The magnitude–frequency distribution (MFD), which quantifies the relative frequency of large versus small earthquakes, is commonly used in seismic hazard assessment studies and is thought to characterize earthquake dynamics. The classic Gutenberg–Richter (GR) model posits that earthquake frequency decays exponentially with magnitude. The tapered Gutenberg–Richter (TGR) model is a variant that assumes a further reduced frequency of larger earthquakes. Distinguishing which of these two distributions better fits observations is important not only for a better understanding of earthquake physics but also for robust forecasting of earthquake magnitudes. Therefore, we evaluate methods used to differentiate these two distributions and their statistical significance given a set of observations. We find the likelihood-ratio test to be the most effective approach. It rarely misclassifies a GR distribution as a TGR distribution, whereas a TGR distribution can be misclassified as GR when the tail of the MFD is insufficiently sampled. We demonstrate that the probability of correctly identifying a TGR model exceeds 90% when the corner magnitude is one unit smaller than the maximum magnitude predicted by the GR distribution. Furthermore, we introduce an objective framework aimed at detecting potential temporal shifts between the two distributions. We apply this framework to global seismicity and two observational cases of induced seismicity. The MFD of global seismicity shows transitions between GR and TGR distributions over time, which might be explained by either inherent temporal variation in behavior or by the random sampling of a bilinear GR model with a larger b value for M >7.6. Regarding the induced seismicity cases, we demonstrate significant and persistent TGR distributions in seismicity induced by geothermal well stimulations at Otaniemi, Finland. Furthermore, we find that earthquakes in the Coso geothermal field (California) exhibit TGR behavior during a specific period, likely influenced by the type of magnitude scale used.
", "doi": "10.1785/0120250130", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2026-02", "series_number": "1", "volume": "116", "issue": "1", "pages": "436-466" }, { "id": "authors:d923p-3kx34", "collection": "authors", "collection_id": "d923p-3kx34", "cite_using_url": "https://authors.library.caltech.edu/records/d923p-3kx34", "type": "article", "title": "Data Assimilation in Machine-Learned Reduced-order Model of Chaotic Earthquake Sequences", "author": [ { "family_name": "Kaveh", "given_name": "Hojjat", "orcid": "0000-0003-3272-3417", "clpid": "Kaveh-Hojjat" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Stuart", "given_name": "Andrew M.", "orcid": "0000-0001-9091-7266", "clpid": "Stuart-A-M" } ], "abstract": "Realistic models of earthquake sequences can be simulated by assuming faults governed by rate-and-state friction embedded in an elastic medium. Exploring the possibility of using such models for earthquake forecasting is challenging due to the difficulty of integrating Partial Differential Equation (PDE) models with sparse, low-resolution observational data. This paper presents a machine-learning-based reduced-order model (ROM) for earthquake sequences that addresses this limitation. The proposed ROM captures the slow/fast chaotic dynamics of earthquake sequences using a low-dimensional representation, enabling computational efficiency and robustness to high-frequency noise in observational data. The ROM's efficiency facilitates effective data assimilation using the Ensemble Kalman Filter (EnKF), even with low-resolution, noisy observations. Results demonstrate the ROM's ability to replicate key scaling properties of the sequence -namely the magnitude-frequency, moment-duration, and moment-area relationships- and to estimate the distributions of fault slip rate and state variable, enabling predictions of large events in time and space with uncertainty quantification. These findings underscore the ROM's potential for forecasting and for addressing challenges in inverse problems for nonlinear geophysical systems.
", "doi": "10.1093/gji/ggaf518", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2026-02", "series_number": "2", "volume": "244", "issue": "2", "pages": "ggaf518" }, { "id": "authors:yg2w5-28x43", "collection": "authors", "collection_id": "yg2w5-28x43", "cite_using_url": "https://authors.library.caltech.edu/records/yg2w5-28x43", "type": "article", "title": "Coulomb stress-based forecasting of injection-induced seismicity in Oklahoma and Kansas", "author": [ { "family_name": "Marty", "given_name": "S.", "orcid": "0000-0001-8083-3237", "clpid": "Marty-Samson" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Langenbruch", "given_name": "C." }, { "family_name": "Curry", "given_name": "W." } ], "abstract": "Induced seismicity in Oklahoma and South Kansas has been widely attributed to wastewater disposal into the deep Arbuckle formation. However, the relative contributions of pore-pressure diffusion and poroelastic stress changes to earthquake triggering remain debated. In this study, we apply the Coulomb threshold rate-and-state seismicity forecasting model of Heimisson et al. (2022) to induced seismicity in the region from 2000 to 2024. Our model is informed by poroelastic stress changes resulting from wastewater injection between 1995 and 2024 and is benchmarked against existing seismicity forecast models. Despite its simplicity, our model accurately reproduces the onset, peak, and decline of seismicity, demonstrating strong agreement with the observed earthquake activity in space and time. It provides robust constraints on permeability, yielding a range consistent with previously reported values. Based on the fit to the data, the model informed by poroelastic stress changes performs better. However, regardless of the assumed mechanism, both models yield similarly reliable seismicity forecasts, indicating that the choice of mechanism has a limited impact on forecasting performance. Finally, we estimate the probability of an M w ≥ 5 event occurring between 2021 and 2024 to range from 7% to 18% and conclude that seismic risk will remain elevated if wastewater injection volumes into the Arbuckle persist at similar levels in the coming years.
", "doi": "10.1016/j.epsl.2025.119677", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2025-12-01", "volume": "671", "pages": "119677" }, { "id": "authors:s13sy-cbz83", "collection": "authors", "collection_id": "s13sy-cbz83", "cite_using_url": "https://authors.library.caltech.edu/records/s13sy-cbz83", "type": "article", "title": "Single-well based control and optimization of hydraulic stimulation and induced seismicity: Application to the Otaniemi geothermal project", "author": [ { "family_name": "Kim", "given_name": "Taeho", "orcid": "0000-0002-2560-7728", "clpid": "Kim-Taeho" }, { "family_name": "Guti\u00e9rrez-Oribio", "given_name": "Diego" }, { "family_name": "Stefanou", "given_name": "Ioannis", "orcid": "0000-0002-4552-7717" }, { "family_name": "Acosta", "given_name": "Mateo", "orcid": "0000-0002-0098-7912", "clpid": "Acosta-Mateo" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "In this study, we apply control theory to mitigate earthquake hazards to a stress-based model of enhanced geothermal stimulation. The model considers pore pressure diffusion as the main stressing mechanism and rate-and-state friction as the shear failure mechanism. The controller is designed to follow a given average pressure and the probability of exceedance of a red-light earthquake (the magnitude at which the stimulation would have to stop by regulation) within chosen volumes surrounding the injection source and within a target time. We rigorously prove that the proposed controller can effectively force two output types within the system to given references, despite the presence of model uncertainties, and with minimal system information, using a continuous control signal. This framework is applied to a validated model of the 2018 Otaniemi geothermal stimulation. We use a suite of simulations to identify injection scenarios that outperform the 2018 Otaniemi stimulation. The optimal stimulation achieves higher average pressure in a shorter time with lower seismic hazard. The controller can help determine whether a combination of safety thresholds and optimization targets is feasible and economical. The control framework could be used to design stimulation schedules for enhanced geothermal systems.", "doi": "10.1016/j.geothermics.2025.103396", "issn": "0375-6505", "publisher": "Elsevier", "publication": "Geothermics", "publication_date": "2025-11", "volume": "132", "pages": "103396" }, { "id": "authors:qw1bk-24f09", "collection": "authors", "collection_id": "qw1bk-24f09", "cite_using_url": "https://authors.library.caltech.edu/records/qw1bk-24f09", "type": "article", "title": "The 2025 Mw 7.7 Mandalay, Myanmar, earthquake reveals a complex earthquake cycle with clustering and variable segmentation on the Sagaing Fault", "author": [ { "family_name": "Antoine", "given_name": "Solene L.", "clpid": "Antoine-Solene-L" }, { "family_name": "Shrestha", "given_name": "Rajani", "clpid": "Shrestha-Rajani" }, { "family_name": "Milliner", "given_name": "Chris", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Chris" }, { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Rollins", "given_name": "Chris" }, { "family_name": "Wang", "given_name": "Kang" }, { "family_name": "Chen", "given_name": "Kejie" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We use remote sensing observations to document surface deformation caused by the 2025 Mw 7.7 Mandalay earthquake. This event is a unique case of an extremely long (~510 km) and sustained supershear rupture probably favored by the rather smooth and continuous geometry of this section of the structurally mature Sagaing Fault. The seismic rupture involved the locked portion of the fault over its entire depth extent (0 to 13 km) with a remarkably uniform slip distribution that averages 3.3 m, and an average stress drop of 4.7 MPa. No shallow-slip deficit is observed. The rupture extent challenges usual scaling laws relating earthquake magnitude, fault length, and slip. The fault ruptured along a known seismic gap that last ruptured in 1839 and tailed off into sections that ruptured during large earthquakes in 1930 and 1946. The amplitude and spatial distribution of fault slip in the 2025 event conform only approximatively to the slip-predictable model and the segmentation inferred from the fault geometry and past ruptures. Plausible sequences of earthquakes with variable magnitude, segmentation, and return periods, including events similar to the 2025 earthquake are produced in quasidynamic simulations using a simplified but nonplanar fault geometry. Based on this simulation, Mw >7.5 events return irregularly with an interevent time of ~141 y on average and a SD of ~40 y. The simulation is consistent with the historical seismicity and with the maximum magnitude ~Mw 7.9 and return period (~250 y) derived from moment conservation. Data assimilation into such simulations could provide a way for time-dependent hazard assessment in the future.
", "doi": "10.1073/pnas.2514378122", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences", "publication_date": "2025-08-11", "series_number": "33", "volume": "122", "issue": "33", "pages": "e2514378122" }, { "id": "authors:5rrnd-av351", "collection": "authors", "collection_id": "5rrnd-av351", "cite_using_url": "https://authors.library.caltech.edu/records/5rrnd-av351", "type": "article", "title": "Localization of inelastic strain with fault maturity and effects on earthquake characteristics", "author": [ { "family_name": "Milliner", "given_name": "C.", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Chris" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Dolan", "given_name": "J. F." }, { "family_name": "Hollingsworth", "given_name": "J.", "orcid": "0000-0003-0122-296X" } ], "abstract": "Coseismic ruptures release stored elastic strain through a combination of shear displacement along localized, principal faults and distributed bulk inelastic failure of the surrounding material. How inelastic strain localizes as fault systems mature and structurally develop is less well understood owing to the difficulty of measuring the complex, near-field and high-strain regions of coseismic surface ruptures. Here we use radar and optical images to measure the near-field surface displacement field and magnitude of off-fault inelastic strain from 16 historic strike-slip earthquakes that occurred on faults with cumulative displacements and fault slip rates that span almost three orders of magnitude. We show that inelastic shear deformation does localize as fault systems mature: the magnitude of off-fault inelastic strain is largest (34–67%) for fault systems with the lowest cumulative displacements (<3 km) and then rapidly decays to values that saturate around 13–19% for the most ‘mature’ fault systems with cumulative displacements exceeding ~20 km. We find that more localized coseismic ruptures host faster ruptures, generate fewer aftershocks and occur along geometrically simpler fault networks.
\nWe present a method for earthquake causal attribution, which allows us to quantify the probability that an event is due to tectonic loading, a previous earthquake, or a fluid injection. The method is an extension of the stochastic declustering algorithm of Marsan and Lengliné (2008). Earthquake triggering is represented by nonparametric, mean-field kernels, which scale linearly with the seismic moment or hydraulic energy of the trigger. The kernels are estimated based on a linear intensity model via expectation–maximization, with uncertainties derived from Gaussian approximation of the incomplete-data likelihood. Some general implications of the resulting probabilistic causal structure, including an explicit algorithm to quantify the cascading effects, are illustrated. The estimators are validated using synthetic catalogs generated with an extended epidemic-type aftershock sequence model, which accounts for injection-induced earthquakes. Application to southern California seismicity and comparisons with the nearest-neighbor distance declustering method support the linearity assumption in the seismic moment. Application to seismicity related to CO2 injection in the Illinois Basin-Decatur Project (for the period 2011–2014) reveals that 11% of the earthquakes were directly triggered by injection, 89% were due to previous earthquakes, whereas the contribution from tectonic loading was negligible (<1%). The earthquake interaction kernels in both cases show ∼1/t decay in time and indicate triggering by elastic static stress transfer; the injection kernels in the Decatur case suggest pore-pressure diffusion as a more likely mechanism than poroelasticity. The Gutenberg–Richter b-value is estimated to be larger for anthropogenic events (∼1.4) than natural ones (∼1.0). Deviations from the model suggest spatial anisotropy of earthquake interaction in both natural and induced settings.
", "doi": "10.1785/0120240233", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2025-08", "series_number": "4", "volume": "115", "issue": "4", "pages": "1406-1434" }, { "id": "authors:7kjwy-7aa70", "collection": "authors", "collection_id": "7kjwy-7aa70", "cite_using_url": "https://authors.library.caltech.edu/records/7kjwy-7aa70", "type": "article", "title": "Finite Size Effects on Seismicity Induced by Fluid Injection in a Discrete Fault Network With Rate-and-State Friction", "author": [ { "family_name": "Kim", "given_name": "Taeho", "orcid": "0000-0002-2560-7728", "clpid": "Kim-Taeho" }, { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The seismicity rate model of J. Dieterich (1994, A constitutive law for rate of earthquake production and its application to earthquake clusteringhttps://doi.org/10.1029/93jb02581) has been used extensively in recent years to model induced seismicity in fluid injection settings. In this study, we highlight its major assumptions and examine how they may bias the interpretations of inferred model parameters when applied to induced seismicity observed in real reservoirs. We do so by comparing the model to numerical simulations of induced earthquakes in a discrete fault network (DFN). The seismicity patterns show significant differences between the DFN and Dietrich model. In particular, DFN simulations show the development of a backfront during the injection due to the exhaustion of available nucleation sources and a shut-off of near-well seismicity due to aseismic slip at high pore pressure. When matched to the DFN catalogs, both the background seismicity rate parameter, Rb, and the direct effect rate-and-state friction parameter, a, of the Dieterich model both significantly underestimate the same parameters of the DFN. We recall the seismicity induced by the 1993 stimulation of the GPK1 injection well in Soultz-Sous-Forts for evidence of co-injection backfronts and aseismic slip among small faults. We do not discount the use of the Dieterich model—they successfully reproduce seismicity simulated from a wide range of initial conditions and fault network conditions—but emphasize that interpretations of inferred parameters must take into account finite size effects that are neglected by the model's original assumptions.
", "doi": "10.1029/2024jb030243", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research: Solid Earth", "publication_date": "2025-07", "series_number": "7", "volume": "130", "issue": "7", "pages": "e2024JB030243" }, { "id": "authors:1zxnv-e5h76", "collection": "authors", "collection_id": "1zxnv-e5h76", "cite_using_url": "https://authors.library.caltech.edu/records/1zxnv-e5h76", "type": "article", "title": "Physics-Informed Deep Learning for Estimating the Spatial Distribution of Frictional Parameters in Slow Slip Regions", "author": [ { "family_name": "Fukushima", "given_name": "Rikuto", "orcid": "0009-0007-0463-1458" }, { "family_name": "Kano", "given_name": "Masayuki", "orcid": "0000-0002-7288-4760" }, { "family_name": "Hirahara", "given_name": "Kazuro", "orcid": "0000-0002-5065-2985" }, { "family_name": "Ohtani", "given_name": "Makiko", "orcid": "0000-0001-5321-502X" }, { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Slow slip events (SSEs) have been observed in many subduction zones and are understood to result from frictional unstable slip on the plate interface. The diversity of their characteristics and the fact that interplate slip can also be seismic suggest that frictional properties are heterogeneous. We are however lacking methods to determine spatial variations of frictional properties. In this paper, we employ a Physics\u2010Informed Neural Network (PINN) to achieve this goal using a synthetic model inspired by the long\u2010term SSEs observed in the Bungo channel. PINN is a deep learning technique that can be used to solve the differential equations representing the physics of the problem and determine the model parameters from observations. We start with an idealized case where it is assumed that fault slip is directly observed. We next move to a more realistic case where the observations consist of synthetic surface displacement velocity data measured by virtual GNSS stations. We find that the geometry and friction properties of the velocity weakening region, where the slip instability develops, are well estimated, especially if surface displacement velocity above the velocity weakening region is observed. Our PINN\u2010based method can be seen as an inversion technique with the regularization constraint that fault slip obeys a particular friction law. This approach remediates the issue that standard regularization techniques are based on non\u2010physical constraints. Our results show that the PINN\u2010based method is a promising approach for estimating the spatial distribution of friction parameters from GNSS observations.
", "doi": "10.1029/2024jb030256", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research: Solid Earth", "publication_date": "2025-05", "series_number": "5", "volume": "130", "issue": "5", "pages": "e2024JB030256" }, { "id": "authors:ve6rw-xn310", "collection": "authors", "collection_id": "ve6rw-xn310", "cite_using_url": "https://authors.library.caltech.edu/records/ve6rw-xn310", "type": "article", "title": "Maximum Magnitude of Induced Earthquakes in Rate and State Friction Framework", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We analyze the evolution of the rupture radius and maximum magnitude (M_(max)) of injection-induced earthquakes on faults obeying rates and state friction. We define the radii of two different slip modes, aseismic (R^a) and seismic slip (R^s), and derive an expression for maximum magnitude evolution. If the flow rate is sufficiently high, the seismic moment grows with the scaled injection volume, Qt/wS, as M∼C_f(Qt/wS)^(3/2), in which C_f depends on the initial stress level, S is storage coefficient, and w is the thickness of the reservoir. These findings are confirmed using numerical simulations conducted with varied initial states. The simulations show that R^s behaves as a rupture arrest radius and R^a behaves as the minimum possible radius of aseismic creep at a given injection volume. The M_(max) evolution curve can be steeper if the fault is slightly critically stressed. A high-flow rate results in frequent seismic events, starting at relatively low-injected volume, which helps track the evolution of M_(max), providing a way to anticipate the risk of a large event. Conversely, a low-flow rate allows for a larger volume injection without seismic events but may lead to sudden large events without precursory events.
", "doi": "10.1785/0220240382", "issn": "0895-0695", "publisher": "Seismological Society of America", "publication": "Seismological Research Letters", "publication_date": "2025-05", "series_number": "3", "volume": "96", "issue": "3", "pages": "1654-1664" }, { "id": "authors:vbhry-09e90", "collection": "authors", "collection_id": "vbhry-09e90", "cite_using_url": "https://authors.library.caltech.edu/records/vbhry-09e90", "type": "article", "title": "Geodetic Monitoring of Elastic and Inelastic Deformation in Compacting Reservoirs Due To Subsurface Operations", "author": [ { "family_name": "Li", "given_name": "Yuexin", "orcid": "0000-0002-0160-7504", "clpid": "Li-Yuexin" }, { "family_name": "Acosta", "given_name": "Mateo", "orcid": "0000-0002-0098-7912", "clpid": "Acosta-Mateo" }, { "family_name": "Sirorattanakul", "given_name": "Krittanon", "orcid": "0000-0003-2310-8447", "clpid": "Sirorattanakul-Krittanon" }, { "family_name": "Bourne", "given_name": "Stephen", "orcid": "0000-0003-2925-8411" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "A variety of geo-energy operations involve extraction or injections of fluids, including hydrocarbon production or storage, hydrogen storage, CO2 sequestration, and geothermal energy production. The surface deformation resulting from such operations can be a source of information on reservoir geomechanical properties as we show in this study. We analyze the time-dependent surface deformation in the Groningen region in northeastern Netherlands using a comprehensive geodetic data set, which includes InSAR (Radarsat2, TerraSAR-X, Sentinel-1), GNSS, and optical leveling spanning several decades. We resort to an Independent Component Analysis (ICA) to isolate deformation signals of various origins. The signals related to gas production from the Groningen gas field and from seasonal storage at Norg Underground Gas Storage are clearly revealed. Surface deformation associated to the Groningen reservoir show decadal subsidence, with spatially variable subsidence rates dictated by local compressibility. The ICA reveals distinct seasonal fluctuations at Norg, closely mirroring the variations of gas storage. By comparing the observed long-term subsidence within the Groningen reservoir and seasonal oscillations at Norg from a linear poroelastic compaction model, we quantify the fraction of inelastic deformation of the reservoir in space and time and constrain the reservoir compressibility. In Groningen, increased compressibility indicates inelastic compaction that has built over time and might account for as much as 20% of the total compaction cumulated until 2021, while Norg shows no signs of inelastic deformation and a constant compressibility. This study provides a methodology to monitor and calibrate models of the subsurface deformation induced by geo-energy operations or aquifer management.
\nSeismic and aseismic slip events result from episodic slips on faults and are often chaotic due to stress heterogeneity. Their predictability in nature is a widely open question. In this study, we forecast extreme events in a numerical model. The model, which consists of a single fault governed by rate-and-state friction, produces realistic sequences of slow events with a wide range of magnitudes and interevent times. The complex dynamics of this system arise from partial ruptures. As the system self-organizes, the state of the system is confined to a chaotic attractor of a relatively small dimension. We identify the instability regions within this attractor where large events initiate. These regions correspond to the particular stress distributions that are favourable for near complete ruptures of the fault. We show that large events can be forecasted in time and space based on the determination of these instability regions in a low-dimensional space and the knowledge of the current slip rate on the fault.
", "doi": "10.1093/gji/ggae417", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2025-02", "series_number": "2", "volume": "240", "issue": "2", "pages": "870-885" }, { "id": "authors:h8cra-3zt96", "collection": "authors", "collection_id": "h8cra-3zt96", "cite_using_url": "https://authors.library.caltech.edu/records/h8cra-3zt96", "type": "article", "title": "Bursts of Fast Propagating Swarms of Induced Earthquakes at the Groningen Gas Field", "author": [ { "family_name": "Sirorattanakul", "given_name": "Krittanon", "orcid": "0000-0003-2310-8447", "clpid": "Sirorattanakul-Krittanon" }, { "family_name": "Wilding", "given_name": "John D.", "orcid": "0000-0002-0914-2078", "clpid": "Wilding-John-D" }, { "family_name": "Acosta", "given_name": "Mateo", "orcid": "0000-0002-0098-7912", "clpid": "Acosta-Mateo" }, { "family_name": "Li", "given_name": "Yuexin", "orcid": "0000-0002-0160-7504", "clpid": "Li-Yuexin" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Bourne", "given_name": "Stephen J.", "orcid": "0000-0003-2925-8411" }, { "family_name": "van Elk", "given_name": "Jan" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Gas extraction from the Groningen gas reservoir, located in the northeastern Netherlands, has led to a drop in pressure and drove compaction and induced seismicity. Stress\u2010based models have shown success in forecasting induced seismicity in this particular context and elsewhere, but they generally assume that earthquake clustering is negligible. To assess earthquake clustering at Groningen, we generate an enhanced seismicity catalog using a deep\u2010learning\u2010based workflow. We identify and locate 1369 events between 2015 and 2022, including 660 newly detected events not previously identified by the standard catalog from the Royal Netherlands Meteorological Institute. Using the nearest\u2010neighbor distance approach, we find that 72% of events are background independent events, whereas the remaining 28% belong to clusters. The 55% of the clustered events are swarm\u2010like, whereas the rest are aftershock\u2010like. Among the swarms include five newly identified sequences propagating at high velocities between 3 and 50 km/day along directions that do not follow mapped faults or existing structures and frequently exhibit a sharp turn in the middle of the sequence. The swarms occurred around the time of the maximum compaction rate between November 2016 and May 2017 in the Zechstein layer, above the anhydrite caprock, and well\u2010above the directly induced earthquakes that occur within the reservoir and caprock. We suggest that these swarms are related to the aseismic deformation within the salt formation rather than fluids. This study suggests that the propagating swarms do not always signify fluid migration.
\n\nThis study presents and validates a workflow that quantitatively links the rate of barchan dunes migration, which can be measured from remote sensing, to the wind velocity, either measured at a meteorological station or extracted from reanalysis data. The workflow requires the selection of a sand transport law and a procedure to estimate the effect of the local topography on the near surface airflow, namely the speed-up effect, that results from the compression of streamlines as the wind climbs up the dune topography. Additionally, the estimate of sand flux under natural conditions needs to account for short duration wind gusts which are usually not fully accounted for or sampled in climatic models. Those spatial and temporal variations of wind speed have a strong influence on the local sand flux due to the non-linearity of the sand transport models. We investigate these effects by using computational fluid dynamic (CFD) modeling to estimate the speed-up effect on airflow and sand transport. We next include that effect to compare the predicted dune migration rate with remote sensing observations, at two desert barchan dune fields located along the southern rim of the Arabia Gulf. We find that, at the two sites, the speed-up effect increases the predicted sand flux by a factor of ∼3 and that the measured and predicted dune migration rates agree well if the sand transport law of Kok et al. (2012) is used, combined with the cessation threshold from Pähtz and Durán (2023) along with reanalysis data ERA5-Land with an hourly sampling. The proposed workflow is applicable to any barchan dune field on Earth or Mars.
", "doi": "10.1016/j.epsl.2024.119049", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2024-12-15", "volume": "648", "pages": "119049" }, { "id": "authors:85316-00r22", "collection": "authors", "collection_id": "85316-00r22", "cite_using_url": "https://authors.library.caltech.edu/records/85316-00r22", "type": "article", "title": "Earthquake Growth Inhibited at Higher Coulomb Stress Change Rate at Groningen", "author": [ { "family_name": "Tamama", "given_name": "Y.", "orcid": "0000-0002-8363-0272", "clpid": "Tamama-Yuri" }, { "family_name": "Acosta", "given_name": "M.", "orcid": "0000-0002-0098-7912", "clpid": "Acosta-Mateo" }, { "family_name": "Bourne", "given_name": "S. J.", "orcid": "0000-0003-2925-8411" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Gas extraction from the Groningen gas field resulted in significant induced seismicity. We analyze the magnitude\u2010frequency distribution of these earthquakes in space, time and in view of stress changes calculated based on gas production and reservoir properties. Previous studies suggested variations related to reservoir geometry and stress. While we confirm the spatial variations, we do not detect a clear sensitivity of b\u2010value to Coulomb stress changes. However, we find that b\u2010value correlates positively with the rate of Coulomb stress changes. This correlation is statistically significant and robust to uncertainties related to stress change calculation. This study thus points to a possible influence of stress change rate on the probability of the magnitude of induced earthquakes.
", "doi": "10.1029/2024gl110139", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2024-10-28", "series_number": "20", "volume": "51", "issue": "20", "pages": "e2024GL110139" }, { "id": "authors:h6c5d-r0547", "collection": "authors", "collection_id": "h6c5d-r0547", "cite_using_url": "https://authors.library.caltech.edu/records/h6c5d-r0547", "type": "article", "title": "Permafrost slows Arctic riverbank erosion", "author": [ { "family_name": "Geyman", "given_name": "Emily C.", "orcid": "0000-0003-4349-9350", "clpid": "Geyman-Emily-C" }, { "family_name": "Douglas", "given_name": "Madison M.", "orcid": "0000-0002-0762-4719", "clpid": "Douglas-Madison-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" } ], "abstract": "The rate of river migration affects the stability of Arctic infrastructure and communities and regulates the fluxes of carbon, nutrients and sediment to the oceans. However, predicting how the pace of river migration will change in a warming Arctic has so far been stymied by conflicting observations about whether permafrost primarily acts to slow or accelerate river migration. Here we develop new computational methods that enable the detection of riverbank erosion at length scales 5–10 times smaller than the pixel size in satellite imagery, an innovation that unlocks the ability to quantify erosion at the sub-monthly timescales when rivers undergo their largest variations in water temperature and flow. We use these high-frequency observations to constrain the extent to which erosion is limited by the thermal condition of melting the pore ice that cements bank sediment, a requirement that will disappear when permafrost thaws, versus the mechanical condition of having sufficient flow to transport the sediment comprising the riverbanks, a condition experienced by all rivers. Analysis of high-resolution data from the Koyukuk River, Alaska, shows that the presence of permafrost reduces erosion rates by 47%. Using our observations, we calibrate and validate a numerical model that can be applied to diverse Arctic rivers. The model predicts that full permafrost thaw may lead to a 30–100% increase in the migration rates of Arctic rivers.
", "doi": "10.1038/s41586-024-07978-w", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2024-10-10", "series_number": "8033", "volume": "634", "issue": "8033", "pages": "359-365" }, { "id": "authors:s6vdv-qvq81", "collection": "authors", "collection_id": "s6vdv-qvq81", "cite_using_url": "https://authors.library.caltech.edu/records/s6vdv-qvq81", "type": "article", "title": "Quake-DFN: A Software for Simulating Sequences of Induced Earthquakes in a Discrete Fault Network", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We present an earthquake simulator, Quake\u2010DFN, which allows simulating sequences of earthquakes in a 3D discrete fault network governed by rate and state friction. The simulator is quasi\u2010dynamic, with inertial effects being approximated by radiation damping and a lumped mass. The lumped mass term allows for accounting for inertial overshoot and, in addition, makes the computation more effective. Quake\u2010DFN is compared against three publicly available simulation results: (1) the rupture of a planar fault with uniform prestress (SEAS BP5\u2010QD), (2) the propagation of a rupture across a stepover separating two parallel planar faults (RSQSim and FaultMod), and (3) a branch fault system with a secondary fault splaying from a main fault (FaultMod). Examples of injection\u2010induced earthquake simulations are shown for three different fault geometries: (1) a planar fault with a wide range of initial stresses, (2) a branching fault system with varying fault angles and principal stress orientations, and (3) a fault network similar to the one that was activated during the 2011 Prague, Oklahoma, earthquake sequence. The simulations produce realistic earthquake sequences. The time and magnitude of the induced earthquakes observed in these simulations depend on the difference between the initial friction and the residual friction \ud835\udf07\u1d62−\ud835\udf07\u0562, the value of which quantifies the potential for runaway ruptures (ruptures that can extend beyond the zone of stress perturbation due to the injection). The discrete fault simulations show that our simulator correctly accounts for the effect of fault geometry and regional stress tensor orientation and shape. These examples show that Quake\u2010DFN can be used to simulate earthquake sequences and, most importantly, magnitudes, possibly induced or triggered by a fluid injection near a known fault system.
", "doi": "10.1785/0120230299", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2024-10", "series_number": "5", "volume": "114", "issue": "5", "pages": "2341-2358" }, { "id": "authors:vtw8j-9bw14", "collection": "authors", "collection_id": "vtw8j-9bw14", "cite_using_url": "https://authors.library.caltech.edu/records/vtw8j-9bw14", "type": "article", "title": "Super-shear ruptures steered by pre-stress heterogeneities during the 2023 Kahramanmara\u015f earthquake doublet", "author": [ { "family_name": "Chen", "given_name": "Kejie", "orcid": "0000-0002-8878-1731" }, { "family_name": "Wei", "given_name": "Guoguang", "orcid": "0000-0002-8942-5659" }, { "family_name": "Milliner", "given_name": "Christopher", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Christopher" }, { "family_name": "Dal Zilio", "given_name": "Luca", "orcid": "0000-0002-5642-0894" }, { "family_name": "Liang", "given_name": "Cunren", "orcid": "0000-0003-3938-426X" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The 2023 M7.8 and M7.5 earthquake doublet near Kahramanmara\u015f, Turkey, provides insight regarding how large earthquakes rupture complex faults. Here we determine the faults geometry using surface ruptures and Synthetic Aperture Radar measurements, and the rupture kinematics from the joint inversion of high-rate Global Navigation Satellite System (GNSS), strong-motion waveforms, and GNSS static displacement. The M7.8 event initiated on a splay fault and subsequently propagated along the main East Anatolian Fault with an average rupture velocity between 3.0 and 4.0 km/s. In contrast, the M7.5 event demonstrated a bilateral supershear rupture of about 5.0–6.0 km/s over an 80 km length. Despite varying strike and dip angles, the sub-faults involved in the mainshock are nearly optimally oriented relative to the local stress tensor. The second event ruptured a fault misaligned with respect to the regional stress, also hinting at the effect of local stress heterogeneity in addition to a possible free surface effect.
", "doi": "10.1038/s41467-024-51446-y", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2024-08-14", "series_number": "1", "volume": "15", "issue": "1", "pages": "7004" }, { "id": "authors:mbeak-rzs62", "collection": "authors", "collection_id": "mbeak-rzs62", "cite_using_url": "https://authors.library.caltech.edu/records/mbeak-rzs62", "type": "article", "title": "Fault Orientation Trumps Fault Maturity in Controlling Coseismic Rupture Characteristics of the 2021 Maduo Earthquake", "author": [ { "family_name": "Liu\u2010Zeng", "given_name": "Jing", "orcid": "0000-0001-7108-6452", "clpid": "Liu\u2010Zeng-Jing" }, { "family_name": "Liu", "given_name": "Zhijun", "clpid": "Liu-Zhijun" }, { "family_name": "Liu", "given_name": "Xiaoli", "clpid": "Liu-Xiaoli" }, { "family_name": "Milliner", "given_name": "Chris", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Chris" }, { "family_name": "Rodriguez Padilla", "given_name": "Alba M.", "orcid": "0000-0003-0696-2190", "clpid": "Rodriguez-Padilla-Alba-M" }, { "family_name": "Xu", "given_name": "Shiqing", "orcid": "0000-0001-5968-1320", "clpid": "Xu-Shiqing" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Yao", "given_name": "Wenqian", "orcid": "0000-0001-6728-0391", "clpid": "Yao-Wenqian" }, { "family_name": "Klinger", "given_name": "Yann", "orcid": "0000-0003-2119-6391", "clpid": "Klinger-Yann" }, { "family_name": "Han", "given_name": "Longfei", "orcid": "0000-0003-4909-4960", "clpid": "Han-Longfei" }, { "family_name": "Shao", "given_name": "Yanxiu", "orcid": "0000-0002-3281-8179", "clpid": "Shao-Yanxiu" }, { "family_name": "Yan", "given_name": "Xiaodong", "clpid": "Yan-Xiaodong" }, { "family_name": "Aati", "given_name": "Saif", "orcid": "0000-0003-1087-832X", "clpid": "Aati-Saif" }, { "family_name": "Shao", "given_name": "Zhigang", "clpid": "Shao-Zhigang" } ], "abstract": "AbstractFault maturity has been proposed to exert a first order control on earthquake rupture, yet direct observations linking individual rupture to long\u2010term fault growth are rare. The 2021 Mw 7.4 Maduo earthquake ruptured the east\u2010growing end of the slow\u2010moving (\u223c1\u00a0mm/yr) Jiangcuo fault in north Tibet, providing an opportunity to examine the relation between rupture characteristics and fault structure. Here we combine field and multiple remote sensing techniques to map the surface rupture at cm\u2010resolution and document comprehensively on\u2010fault offsets and off\u2010fault deformation. The 158 km\u2010long surface rupture consists of misoriented structurally inherited N110\u00b0\u2010striking segments and younger optimally oriented N093\u00b0\u2010striking segments, relative to the regional stress field. Despite being comparatively newly formed, the \u223cN093\u00b0\u2010striking fault segments accommodate more localized strain, with up to 3\u00a0m on\u2010fault left\u2010lateral slip and 25%\u201350% off\u2010fault deformation, and possibly faster rupture speed. These results are in contrast with previous findings showing more localized strain and faster rupture speed on more mature fault segments; instead, our observations suggest that fault orientation with respect to the regional stress can exert a more important control than fault maturity on coseismic rupture behavior when both factors are at play.", "doi": "10.1029/2023av001134", "issn": "2576-604X", "publisher": "American Geophysical Union", "publication": "AGU Advances", "publication_date": "2024-04", "series_number": "2", "volume": "5", "issue": "2", "pages": "e2023AV001134" }, { "id": "authors:6t28z-yy836", "collection": "authors", "collection_id": "6t28z-yy836", "cite_using_url": "https://authors.library.caltech.edu/records/6t28z-yy836", "type": "article", "title": "Induced Seismicity Forecasting with Uncertainty Quantification: Application to the Groningen Gas Field", "author": [ { "family_name": "Kaveh", "given_name": "Hojjat", "orcid": "0000-0003-3272-3417", "clpid": "Kaveh-Hojjat" }, { "family_name": "Batlle", "given_name": "Pau", "orcid": "0000-0003-4886-058X", "clpid": "Battle-Franch-Pau" }, { "family_name": "Acosta", "given_name": "Mateo", "orcid": "0000-0002-0098-7912", "clpid": "Acosta-Mateo-A" }, { "family_name": "Kulkarni", "given_name": "Pranav", "orcid": "0000-0002-1461-0948", "clpid": "Kulkarni-Pranav-D" }, { "family_name": "Bourne", "given_name": "Stephen J.", "orcid": "0000-0003-2925-8411" }, { "family_name": "Avouac", "given_name": "Jean Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Reservoir operations for gas extraction, fluid disposal, carbon dioxide storage, or geothermal energy production are capable of inducing seismicity. Modeling tools exist for seismicity forecasting using operational data, but the computational costs and uncertainty quantification (UQ) pose challenges. We address this issue in the context of seismicity induced by gas production from the Groningen gas field using an integrated modeling framework, which combines reservoir modeling, geomechanical modeling, and stress-based earthquake forecasting. The framework is computationally efficient thanks to a 2D finite-element reservoir model, which assumes vertical flow equilibrium, and the use of semianalytical solutions to calculate poroelastic stress changes and predict seismicity rate. The earthquake nucleation model is based on rate-and-state friction and allows for an initial strength excess so that the faults are not assumed initially critically stressed. We estimate uncertainties in the predicted number of earthquakes and magnitudes. To reduce the computational costs, we assume that the stress model is true, but our UQ algorithm is general enough that the uncertainties in reservoir and stress models could be incorporated. We explore how the selection of either a Poisson or a Gaussian likelihood influences the forecast. We also use a synthetic catalog to estimate the improved forecasting performance that would have resulted from a better seismicity detection threshold. Finally, we use tapered and nontapered Gutenberg–Richter distributions to evaluate the most probable maximum magnitude over time and account for uncertainties in its estimation. Although we did not formally account for uncertainties in the stress model, we tested several alternative stress models, and found negligible impact on the predicted temporal evolution of seismicity and forecast uncertainties. Our study shows that the proposed approach yields realistic estimates of the uncertainties of temporal seismicity and is applicable for operational forecasting or induced seismicity monitoring. It can also be used in probabilistic traffic light systems.
", "doi": "10.1785/0220230179", "issn": "0895-0695", "publisher": "Seismological Society of America", "publication": "Seismological Research Letters", "publication_date": "2024-03", "series_number": "2A", "volume": "95", "issue": "2A", "pages": "773-790" }, { "id": "authors:7x8c3-sr022", "collection": "authors", "collection_id": "7x8c3-sr022", "cite_using_url": "https://authors.library.caltech.edu/records/7x8c3-sr022", "type": "article", "title": "Airborne Sounding Radar for Desert Subsurface Exploration of Aquifers: Desert-SEA: Mission concept study [Space Agencies]", "author": [ { "family_name": "Heggy", "given_name": "Essam", "orcid": "0000-0001-7476-2735", "clpid": "Heggy-Essam" }, { "family_name": "Moghaddam", "given_name": "Mahta", "orcid": "0000-0001-5304-2616" }, { "family_name": "Palmer", "given_name": "Elizabeth M.", "orcid": "0000-0002-4603-3196" }, { "family_name": "Brown", "given_name": "William M." }, { "family_name": "Blanton", "given_name": "J. Lee", "orcid": "0009-0004-3074-4382" }, { "family_name": "Kosinski", "given_name": "Miko\u0142aj" }, { "family_name": "Sirri", "given_name": "Paul" }, { "family_name": "Dixon", "given_name": "Edgar A.", "orcid": "0009-0001-0668-0671" }, { "family_name": "Abotalib", "given_name": "Abotalib Z.", "orcid": "0000-0002-5852-0370" }, { "family_name": "Normand", "given_name": "Jonathan C. L.", "orcid": "0000-0003-0250-9698" }, { "family_name": "Clark", "given_name": "John", "orcid": "0009-0004-0328-662X" }, { "family_name": "Klemens", "given_name": "Gary" }, { "family_name": "Agranier", "given_name": "Matthieu" }, { "family_name": "Guillon", "given_name": "Fran\u00e7ois" }, { "family_name": "Abdellatif", "given_name": "Akram A.", "orcid": "0000-0001-5768-6822" }, { "family_name": "Khattab", "given_name": "Tamer", "orcid": "0000-0003-2347-9555" }, { "family_name": "Tsvetanov", "given_name": "Zlatan", "orcid": "0000-0001-6177-6767" }, { "family_name": "Shokry", "given_name": "Mohamed" }, { "family_name": "Al-Mulla", "given_name": "Noor" }, { "family_name": "Ramah", "given_name": "Mohamed", "orcid": "0000-0001-8831-3236" }, { "family_name": "Bateni", "given_name": "Sayed M.", "orcid": "0000-0002-7134-0067" }, { "family_name": "Tabatabaeenejad", "given_name": "Alireza", "orcid": "0000-0002-5098-8526", "clpid": "Tabatabaeenejad-Alireza" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Deterministic earthquake prediction remains elusive, but time\u2010dependent probabilistic seismicity forecasting seems within reach thanks to the development of physics\u2010based models relating seismicity to stress changes. Difficulties include constraining the earthquake nucleation model and fault initial stress state. Here, we analyze induced earthquakes from the Groningen gas field, where production is strongly seasonal, and seismicity began 3 decades after production started. We use the seismicity response to stress variations to constrain the earthquake nucleation process and calibrate models for time\u2010dependent forecasting of induced earthquakes. Remarkable agreements of modeled and observed seismicity are obtained when we consider (a) the initial strength excess, (b) the finite duration of earthquake nucleation, and (c) the seasonal variations of gas production. We propose a novel metric to quantify the nucleation model's ability to capture the damped amplitude and the phase of the seismicity response to short\u2010timescale (seasonal) stress variations which allows further tightening the model's parameters.
", "doi": "10.1029/2023gl105455", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2023-10-16", "series_number": "19", "volume": "50", "issue": "19", "pages": "e2023GL105455" }, { "id": "authors:dgaad-kdr74", "collection": "authors", "collection_id": "dgaad-kdr74", "cite_using_url": "https://authors.library.caltech.edu/records/dgaad-kdr74", "type": "article", "title": "Cascading foreshocks, aftershocks and earthquake swarms in a discrete fault network", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Earthquakes come in clusters formed of mostly aftershock sequences, swarms and occasional foreshock sequences. This clustering is thought to result either from stress transfer among faults, a process referred to as cascading, or from transient loading by aseismic slip (pre-slip, afterslip or slow slip events). The ETAS statistical model is often used to quantify the fraction of clustering due to stress transfer and to assess the eventual need for aseismic slip to explain foreshocks or swarms. Another popular model of clustering relies on the earthquake nucleation model derived from experimental rate-and-state friction. According to this model, earthquakes cluster because they are time-advanced by the stress change imparted by the mainshock. This model ignores stress interactions among aftershocks and cannot explain foreshocks or swarms in the absence of transient loading. Here, we analyse foreshock, swarm and aftershock sequences resulting from cascades in a Discrete Fault Network model governed by rate-and-state friction. We show that the model produces realistic swarms, foreshocks and aftershocks. The Omori law, characterizing the temporal decay of aftershocks, emerges in all simulations independently of the assumed initial condition. In our simulations, the Omori law results from the earthquake nucleation process due to rate and state friction and from the heterogeneous stress changes due to the coseismic stress transfers. By contrast, the inverse Omori law, which characterizes the accelerating rate of foreshocks, emerges only in the simulations with a dense enough fault system. A high-density complex fault zone favours fault interactions and the emergence of an accelerating sequence of foreshocks. Seismicity catalogues generated with our discrete fault network model can generally be fitted with the ETAS model but with some material differences. In the discrete fault network simulations, fault interactions are weaker in aftershock sequences because they occur in a broader zone of lower fault density and because of the depletion of critically stressed faults. The productivity of the cascading process is, therefore, significantly higher in foreshocks than in aftershocks if fault zone complexity is high. This effect is not captured by the ETAS model of fault interactions. It follows that a foreshock acceleration stronger than expected from ETAS statistics does not necessarily require aseismic slip preceding the mainshock (pre-slip). It can be a manifestation of a cascading process enhanced by the topological properties of the fault network. Similarly, earthquake swarms might not always imply transient loading by aseismic slip, as they can emerge from stress interactions.
", "doi": "10.1093/gji/ggad278", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2023-10", "series_number": "1", "volume": "235", "issue": "1", "pages": "831-852" }, { "id": "authors:rymae-8he11", "collection": "authors", "collection_id": "rymae-8he11", "cite_using_url": "https://authors.library.caltech.edu/records/rymae-8he11", "type": "article", "title": "Probing Shallow Aquifers in Hyperarid Dune Fields Using VHF Sounding Radar", "author": [ { "family_name": "Heggy", "given_name": "Essam", "orcid": "0000-0001-7476-2735", "clpid": "Heggy-Essam" }, { "family_name": "Normand", "given_name": "Jonathan C. L.", "orcid": "0000-0003-0250-9698" }, { "family_name": "Palmer", "given_name": "Elizabeth M.", "orcid": "0000-0002-4603-3196" }, { "family_name": "Scabbia", "given_name": "Giovanni", "orcid": "0000-0002-0246-8366" }, { "family_name": "Al-Maktoumi", "given_name": "Ali K. S.", "orcid": "0000-0001-8766-5993" }, { "family_name": "Mazzoni", "given_name": "Annamaria", "orcid": "0000-0001-7324-5066" }, { "family_name": "Blanton", "given_name": "Lee", "orcid": "0009-0004-3074-4382" }, { "family_name": "Schaefer", "given_name": "Sophie J. N." }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Large-scale characterization of water table depth in shallow aquifers in hyperarid areas provides crucial insights into groundwater dynamics under increasing anthropogenic discharge and climatic fluctuations. Due to their penetration capabilities into arid soils, airborne very-high-frequency (VHF) sounding radars can achieve this objective under specific system design, topographic and geophysical constraints, superseding sporadic well logs, and ground-based surveys that provide compromised assessments of the distribution and depth of these water bodies. One of the least constrained ambiguities limiting the design of such systems, however, is the maximum penetration depth in desiccated sandy soils, which covers a sizeable fraction of desert landscapes. To constrain the latter, we perform a ground survey using 50- and 80-MHz GPRs with effective dynamic ranges of ~80-dB at the surface to probe the unconfined aquifer under desiccated linear dunes in the Wahiba Sands in Oman. Our survey resolves the water table down to at least 69 m depth, the deepest achieved at VHF frequencies in hyperarid terrains. We observe the average two-way plane-wave subsurface radar attenuation, accounting for both dielectric and scattering losses, to range from 0.1 to 1.4 dB/m through these sandy formations. Dielectric and scattering losses can be of equal magnitude depending on the sounding frequency and stratigraphic setting of the subsurface. Penetration depths to the water table are validated with time-domain electromagnetic (TDEM) measurements and well-log data. In addition, we identify shallow paleochannels from L-band synthetic aperture radar (SAR) observations that suggest modern meteoritic recharge of the probed aquifer, creating shallow localized anomalous losses in the radar signal in the first few meters. We conclude that the minimum requirements for an airborne VHF sounding radar to probe shallow aquifers at depths of tens of meters in sandy formations in hyperarid areas are a signal-to-noise ratio (SNR) of 55 dB at the surface, a bandwidth of 10 MHz, and a surface h_(rms) not exceeding 2 m.
", "doi": "10.1109/tgrs.2023.3306286", "issn": "0196-2892", "publisher": "IEEE", "publication": "IEEE Transactions on Geoscience and Remote Sensing", "publication_date": "2023-09-08", "volume": "61", "pages": "4505822" }, { "id": "authors:tc5zd-6bm85", "collection": "authors", "collection_id": "tc5zd-6bm85", "cite_using_url": "https://authors.library.caltech.edu/records/tc5zd-6bm85", "type": "article", "title": "Climatic control on seasonal variations in mountain glacier surface velocity", "author": [ { "family_name": "Nanni", "given_name": "Ugo", "orcid": "0000-0001-6677-6117", "clpid": "Nanni-Ugo" }, { "family_name": "Scherler", "given_name": "Dirk", "orcid": "0000-0003-3911-2803" }, { "family_name": "Ayoub", "given_name": "Francois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-Francois" }, { "family_name": "Millan", "given_name": "Romain", "orcid": "0000-0002-7987-1305" }, { "family_name": "Herman", "given_name": "Frederic", "orcid": "0000-0002-7237-4656" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Accurate measurements of ice flow are essential to predict future changes in glaciers and ice caps. Glacier displacement can in principle be measured on the large scale by cross-correlation of satellite images. At weekly to monthly scales, the expected displacement is often of the same order as the noise for the commonly used satellite images, complicating the retrieval of accurate glacier velocity. Assessments of velocity changes on short timescales and over complex areas such as mountain ranges are therefore still lacking but are essential to better understand how glacier dynamics are driven by internal and external factors. In this study, we take advantage of the wide availability and redundancy of satellite imagery over the western Pamirs to retrieve glacier velocity changes over 10 d intervals for 7 years and for a wide range of glacier geometry and dynamics. Our results reveal strong seasonal trends. In spring/summer, we observe velocity increases of up to 300 % compared to a slow winter period. These accelerations clearly migrate upglacier throughout the melt season, which we link to changes in subglacial hydrology efficiency. In autumn, we observe glacier accelerations that have rarely been observed before. These episodes are primarily confined to the upper ablation zone with a clear downglacier migration. We suggest that they result from glacier instabilities caused by sudden subglacial pressurization in response to (1) supraglacial pond drainage and/or (2) gradual closure of the hydrological system. Our 10 d resolved measurements allow us to characterize the short-term response of glaciers to changing meteorological and climatic conditions.
", "doi": "10.5194/tc-17-1567-2023", "issn": "1994-0424", "publisher": "European Geosciences Union", "publication": "The Cryosphere", "publication_date": "2023-04-11", "series_number": "4", "volume": "17", "issue": "4", "pages": "1567-1583" }, { "id": "authors:anbfn-8dh79", "collection": "authors", "collection_id": "anbfn-8dh79", "cite_using_url": "https://authors.library.caltech.edu/records/anbfn-8dh79", "type": "article", "title": "Stress-Based and Convolutional Forecasting of Injection-Induced Seismicity: Application to the Otaniemi Geothermal Reservoir Stimulation", "author": [ { "family_name": "Kim", "given_name": "Taeho", "orcid": "0000-0002-2560-7728", "clpid": "Kim-Taeho" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Induced seismicity observed during Enhanced Geothermal Stimulation at Otaniemi, Finland is modeled using both statistical and physical approaches. The physical model produces simulations closest to the observations when assuming rate\u2010and\u2010state friction for shear failure with diffusivity matching the pressure build\u2010up at the well\u2010head at onset of injections. Rate\u2010and\u2010state friction implies a time\u2010dependent earthquake nucleation process which is found to be essential in reproducing the spatial pattern of seismicity. This implies that permeability inferred from the expansion of the seismicity triggering front (Shapiro et al., 1997, https://doi.org/10.1111/j.1365-246x.1997.tb01215.x) can be biased. We suggest a heuristic method to account for this bias that is independent of the earthquake magnitude detection threshold. Our modeling suggests that the Omori law decay during injection shut\u2010ins results mainly from stress relaxation by pore pressure diffusion. During successive stimulations, seismicity should only be induced where the previous maximum of Coulomb stress changes is exceeded. This effect, commonly referred to as the Kaiser effect, is not clearly visible in the data from Otaniemi. The different injection locations at the various stimulation stages may have resulted in sufficiently different effective stress distributions that the effect was muted. We describe a statistical model whereby seismicity rate is estimated from convolution of the injection history with a kernel which approximates earthquake triggering by fluid diffusion. The statistical method has superior computational efficiency to the physical model and fits the observations as well as the physical model. This approach is applicable provided the Kaiser effect is not strong, as was the case in Otaniemi.
", "doi": "10.1029/2022jb024960", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research: Solid Earth", "publication_date": "2023-04", "series_number": "4", "volume": "128", "issue": "4", "pages": "e2022JB024960" }, { "id": "authors:00s24-8ta98", "collection": "authors", "collection_id": "00s24-8ta98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230321-823036300.89", "type": "article", "title": "Weak upper-mantle base revealed by postseismic deformation of a deep earthquake", "author": [ { "family_name": "Park", "given_name": "Sunyoung", "orcid": "0000-0002-6660-0047", "clpid": "Park-Sunyoung" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Zhan", "given_name": "Zhongwen", "orcid": "0000-0002-5586-2607", "clpid": "Zhan-Zhongwen" }, { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-Adriano" } ], "abstract": "Mantle viscosity plays a key role in the Earth's internal dynamics and thermal history. Geophysical inferences of the viscosity structure, however, have shown large variability depending on the types of observables used or the assumptions imposed. Here, we study the mantle viscosity structure by using the postseismic deformation following a deep (approximately 560\u2009km) earthquake located near the bottom of the upper mantle. We apply independent component analysis to geodetic time series to successfully detect and extract the postseismic deformation induced by the moment magnitude 8.2, 2018 Fiji earthquake. To search for the viscosity structure that can explain the detected signal, we perform forward viscoelastic relaxation modelling with a range of viscosity structures. We find that our observation requires a relatively thin (approximately 100\u2009km), low-viscosity (10\u00b9\u2077 to 10\u00b9\u2078\u2009Pa\u2009s) layer at the bottom of the mantle transition zone. Such a weak zone could explain the slab flattening and orphaning observed in numerous subduction zones, which are otherwise challenging to explain in the whole mantle convection regime. The low-viscosity layer may result from superplasticity induced by the postspinel transition, weak CaSiO\u2083 perovskite, high water content or dehydration melting.", "doi": "10.1038/s41586-022-05689-8", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2023-03-16", "series_number": "7952", "volume": "615", "issue": "7952", "pages": "455-460" }, { "id": "authors:fzkf9-6mp37", "collection": "authors", "collection_id": "fzkf9-6mp37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221205-666301600.12", "type": "article", "title": "Potential and Limitation of PlanetScope Images for 2-D and 3-D Earth Surface Monitoring With Example of Applications to Glaciers and Earthquakes", "author": [ { "family_name": "Aati", "given_name": "Saif", "orcid": "0000-0003-1087-832X", "clpid": "Aati-Saif" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Rupnik", "given_name": "Ewelina", "orcid": "0000-0002-7229-5501", "clpid": "Rupnik-Ewelina" }, { "family_name": "Deseilligny", "given_name": "Marc-Pierrot", "clpid": "Deseilligny-Marc-Pierrot" } ], "abstract": "The Planet PlanetScope (PS) CubeSat constellation acquires high-resolution optical images that cover the entire surface of the Earth daily, enabling an unprecedented capability to monitor the Earth's surface changes. However, our analysis reveals artifacts of the geometry of PS images related to the imaging system and processing issues, limiting the usability of these data for various Earth science applications, including the monitoring of glaciers, dune motion, or the measurement of ground deformation due to earthquakes and landslides. Here, we analyze these artifacts and propose ways to remediate them. We use two examples to evaluate the data and assess the performance of our proposed approaches. The first is the ground deformation caused by the 2019 Ridgecrest earthquake sequence, California, USA, and the second is the 2018\u20132019 surge of the Shisper glacier in the Karakorum. Using an image correlation technique, we show that PS images exhibit several geometric artifacts, such as scene-to-scene misregistration, inconsistence geolocation accuracy between spectral bands, and topographic artifacts. Altogether, these artifacts make a quantitative analysis of ground displacement difficult and inaccurate. We present a method that remediates most of these geometric artifacts. In addition, we propose a framework for selecting the most appropriate images and a procedure for refining the rational function model (RFM) of unrectified images to monitor surface displacements and topography changes in 3-D. These tools should enhance the use of PS images for Earth science applications.", "doi": "10.1109/tgrs.2022.3215821", "issn": "0196-2892", "publisher": "IEEE", "publication": "IEEE Transactions on Geoscience and Remote Sensing", "publication_date": "2022-11-07", "volume": "60", "pages": "Art. No. 4512919" }, { "id": "authors:eg69j-4an91", "collection": "authors", "collection_id": "eg69j-4an91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230301-701033500.6", "type": "article", "title": "From Macro- to Microscale: A combined modelling approach for near-surface wind flow on Mars at sub-dune length-scales", "author": [ { "family_name": "Love", "given_name": "Richard", "orcid": "0000-0002-8753-4755", "clpid": "Love-Richard" }, { "family_name": "Jackson", "given_name": "Derek W. T.", "orcid": "0000-0003-1778-2187", "clpid": "Jackson-Derek-W-T" }, { "family_name": "Michaels", "given_name": "Timothy", "clpid": "Michaels-Timothy" }, { "family_name": "Smyth", "given_name": "Thomas A. G.", "orcid": "0000-0002-1740-762X", "clpid": "Smyth-Thomas-A-G" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Cooper", "given_name": "Andrew", "clpid": "Cooper-Andrew-P" } ], "abstract": "The processes that initiate and sustain sediment transport which contribute to the modification of aeolian deposits in Mars' low-density atmosphere are still not fully understood despite recent atmospheric modelling. However, detailed microscale wind flow modelling, using Computational Fluid Dynamics at a resolution of <2 m, provides insights into the near-surface processes that cannot be modeled using larger-scale atmospheric modeling. Such Computational Fluid Dynamics simulations cannot by themselves account for regional-scale atmospheric circulations or flow modifications induced by regional km-scale topography, although realistic fine-scale mesoscale atmospheric modeling can. Using the output parameters from mesoscale simulations to inform the input conditions for the Computational Fluid Dynamics microscale simulations provides a practical approach to simulate near-surface wind flow and its relationship to very small-scale topographic features on Mars, particularly in areas which lack in situ rover data. This paper sets out a series of integrated techniques to enable a multi-scale modelling approach for surface airflow to derive surface airflow dynamics at a (dune) landform scale using High Resolution Imaging Science Experiment derived topographic data. The work therefore provides a more informed and realistic Computational Fluid Dynamics microscale modelling method, which will provide more detailed insight into the surface wind forcing of aeolian transport patterns on martian surfaces such as dunes.", "doi": "10.1371/journal.pone.0276547", "pmcid": "PMC9635718", "issn": "1932-6203", "publisher": "Public Library of Science", "publication": "PLoS ONE", "publication_date": "2022-11-04", "series_number": "11", "volume": "17", "issue": "11", "pages": "Art. No. e0276547" }, { "id": "authors:nvgb9-jy854", "collection": "authors", "collection_id": "nvgb9-jy854", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221214-893781900.2", "type": "article", "title": "Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock", "author": [ { "family_name": "Milliner", "given_name": "C. W. D.", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Christopher-W-D" }, { "family_name": "Aati", "given_name": "S.", "orcid": "0000-0003-1087-832X", "clpid": "Aati-Saif" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The variation of stress on faults is important for our understanding of fault friction and the dynamics of earthquake ruptures. However, we still have little observational constraints on their absolute magnitude, or their variations in space and in time over the seismic cycle. Here we use a new geodetic imaging technique to measure the 3D coseismic slip vectors along the 2019 Ridgecrest surface ruptures and invert them for the coseismic stress state. We find that the coseismic stresses show an eastward rotation that becomes increasingly transtensional from south-to-north along the rupture, that matches the known background stress state. We find that the main fault near the M_w 7.1 mainshock hypocenter was critically stressed. Coseismic slip was maximum there and decreased gradually along strike as the fault became less optimally oriented due its curved geometry. The variations of slip and stress along the curved faults are used to infer the static and dynamic fault friction assuming Mohr-Coulomb failure. We find shear stresses of 4\u20139 MPa in the shallow crust (\u223c1.3 km depth) and that fault friction drops from a static, Byerlee-type, value of 0.61 \u00b1 0.14 to a dynamic value of 0.29 \u00b1 0.04 during seismic slip. These values explain quantitatively the slip variations along a transpressional fault bend.", "doi": "10.1029/2022jb024519", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2022-11", "series_number": "11", "volume": "127", "issue": "11", "pages": "Art. No. e2022JB024519" }, { "id": "authors:3m6mr-pa291", "collection": "authors", "collection_id": "3m6mr-pa291", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221117-356919800.1", "type": "article", "title": "The 2020 Westmorland, California Earthquake Swarm as Aftershocks of a Slow Slip Event Sustained by Fluid Flow", "author": [ { "family_name": "Sirorattanakul", "given_name": "Krittanon", "orcid": "0000-0003-2310-8447", "clpid": "Sirorattanakul-Krittanon" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Khoshmanesh", "given_name": "Mostafa", "orcid": "0000-0001-8724-5737", "clpid": "Khoshmanesh-Mostafa" }, { "family_name": "Cochran", "given_name": "Elizabeth S.", "orcid": "0000-0003-2485-4484", "clpid": "Cochran-Elizabeth-S" }, { "family_name": "Acosta", "given_name": "Mateo", "orcid": "0000-0002-0098-7912", "clpid": "Acosta-Mateo" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Swarms are bursts of earthquakes without an obvious mainshock. Some have been observed to be associated with transient aseismic fault slip, while others are thought to be related to fluids. However, the association is rarely quantitative due to insufficient data quality. We use high-quality GPS/GNSS, InSAR, and relocated seismicity to study a swarm of >2,000 earthquakes which occurred between 30 September and 6 October 2020, near Westmorland, California. Using 5 min sampled Global Positioning System (GPS) supplemented with InSAR, we document a spontaneous shallow M_w 5.2 slow slip event that preceded the swarm by 2\u201315 hr. The earthquakes in the early phase were predominantly non-interacting and driven primarily by the slow slip event resulting in a nonlinear expansion. A stress-driven model based on the rate-and-state friction successfully explains the overall spatial and temporal evolution of earthquakes, including the time lag between the onset of the slow slip event and the swarm. Later, a distinct back front and a square root of time expansion of clustered seismicity on en-echelon fault structures suggest that fluids helped sustain the swarm. Static stress triggering analysis using Coulomb stress and statistics of interevent times suggest that 45%\u201365% of seismicity was driven by the slow slip event, 10%\u201335% by inter-earthquake interactions, and 10%\u201330% by fluids. Our model also provides constraints on the friction parameter and the pore pressure and suggests that this swarm behaved like an aftershock sequence but with the mainshock replaced by the slow slip event.", "doi": "10.1029/2022jb024693", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2022-11", "series_number": "11", "volume": "127", "issue": "11", "pages": "Art. No. e2022JB024693" }, { "id": "authors:fgn3t-01z05", "collection": "authors", "collection_id": "fgn3t-01z05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230314-844891400.23", "type": "article", "title": "Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock", "author": [ { "family_name": "Milliner", "given_name": "C. W. D.", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Christopher-W-D" }, { "family_name": "Aati", "given_name": "S.", "orcid": "0000-0003-1087-832X", "clpid": "Aati-Saif" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The variation of stress on faults is important for our understanding of fault friction and the dynamics of earthquake ruptures. However, we still have little observational constraints on their absolute magnitude, or their variations in space and in time over the seismic cycle. Here we use a new geodetic imaging technique to measure the 3D coseismic slip vectors along the 2019 Ridgecrest surface ruptures and invert them for the coseismic stress state. We find that the coseismic stresses show an eastward rotation that becomes increasingly transtensional from south-to-north along the rupture, that matches the known background stress state. We find that the main fault near the M_w 7.1 mainshock hypocenter was critically stressed. Coseismic slip was maximum there and decreased gradually along strike as the fault became less optimally oriented due its curved geometry. The variations of slip and stress along the curved faults are used to infer the static and dynamic fault friction assuming Mohr-Coulomb failure. We find shear stresses of 4\u20139 MPa in the shallow crust (\u223c1.3 km depth) and that fault friction drops from a static, Byerlee-type, value of 0.61 \u00b1 0.14 to a dynamic value of 0.29 \u00b1 0.04 during seismic slip. These values explain quantitatively the slip variations along a transpressional fault bend.", "doi": "10.1029/2022jb024519", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2022-11", "series_number": "11", "volume": "127", "issue": "11", "pages": "Art. No. e2022JB024519" }, { "id": "authors:d6hg7-0hc09", "collection": "authors", "collection_id": "d6hg7-0hc09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220705-346508000", "type": "article", "title": "Linear stability analysis of the condition for vibration during frictional slip", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Slip along a frictional contact between elastic bodies can be stable or unstable, leading to stick-slip motion. Frictional slip can also be associated with vibrations. The condition for these vibrations and their characteristics remains poorly understood. To address this issue, which is relevant to engineering and earth science, we carry out a linear stability analysis of a spring-and-slider system obeying rate and state friction. We first identify the solution space for the linearized equation and define the conditions for different slip modes from the real and imaginary parts of the solution. We then derive asymptotic equations for all boundaries between overdamped stable sliding, inertial/non-inertial underdamped oscillation, stick-slip, and harmonic vibration. Finally, we verified the conditions with numerical simulations. Our work provides rigorous criteria regarding the conditions for the various frictional slip modes and the emergence of vibrations. It can help design appropriate approaches for suppressing undesired vibrations in mechanical systems and investigate the mechanisms generating vibrations (tremor) associated with fault slip in nature.", "doi": "10.1016/j.jmps.2022.104993", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "2022-10", "volume": "167", "pages": "Art. No. 104993" }, { "id": "authors:6bmd6-tfw83", "collection": "authors", "collection_id": "6bmd6-tfw83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221011-459135000.36", "type": "article", "title": "Stress-based forecasting of induced seismicity with instantaneous earthquake failure functions: Applications to the Groningen gas reservoir", "author": [ { "family_name": "Smith", "given_name": "Jonathan D.", "orcid": "0000-0002-1684-1344", "clpid": "Smith-Jonathan-D" }, { "family_name": "Heimisson", "given_name": "El\u00edas R.", "orcid": "0000-0001-8342-7226", "clpid": "Heimisson-El\u00edas-R" }, { "family_name": "Bourne", "given_name": "Stephen J.", "orcid": "0000-0003-2925-8411", "clpid": "Bourne-Stephen-J" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "In this study we use the Groningen gas field to test a new method to assess stress changes due to gas extraction and forecast induced seismicity. We take advantage of the detailed knowledge of the reservoir geometry and production history, and of the availability of surface subsidence measurements and high quality seismicity data. The subsurface is represented as a homogeneous isotropic linear poroelastic half-space subject to stress changes in three-dimensional space due to reservoir compaction and pore pressure variations. The reservoir is represented with cuboidal strain volumes. Stress changes within and outside the reservoir are calculated using a convolution with semi-analytical Green functions. The uniaxial compressibility of the reservoir is spatially variable and constrained with surface subsidence data. We calculate stress changes since the onset of gas production. Coulomb stress changes are maximum near the top and bottom of the reservoir where the reservoir is offset by faults. To assess earthquake probability, we use the standard Mohr-Coulomb failure criterion assuming instantaneous nucleation and a non-critical initial stress. The distribution of initial strength excess, the difference between the initial Coulomb stress and the critical Coulomb stress at failure, is treated as a stochastic variable and estimated from the observations and the modelled stress changes. The exponential rise of seismicity nearly 30 years after the onset of production, provides constraints on the distribution of initial strength. The lag and exponential onset of seismicity are well reproduced assuming either a generalized Pareto distribution, which can represent the tail of any distribution, or a Gaussian distribution, to describe both the tail and body of the distribution. The Gaussian distribution allows to test if the induced seismicity at Groningen has transitioned to the steady-state where seismicity rate is proportional to the stressing rate. We find no evidence that the system has reached such a steady-state regime. The modeling framework is computationally efficient making it possible to test the sensitivity to modeling assumptions regarding the estimation of stress changes. The forecast is found robust to uncertainties about the ability of the model to represent accurately the physical processes. It does not require in particular a priori knowledge of the location and orientation of the faults that can be activated. The method presented here is in principle applicable to induced seismicity in any setting provided deformation and seismicity data are available to calibrate the model.", "doi": "10.1016/j.epsl.2022.117697", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2022-09-15", "volume": "594", "pages": "Art. No. 117697" }, { "id": "authors:5p1y6-0r809", "collection": "authors", "collection_id": "5p1y6-0r809", "cite_using_url": "https://authors.library.caltech.edu/records/5p1y6-0r809", "type": "article", "title": "Surge dynamics of Shisper Glacier revealed by time-series correlation of optical satellite images and their utility to substantiate a generalized sliding law", "author": [ { "family_name": "Beaud", "given_name": "Flavien", "orcid": "0000-0002-0687-8741", "clpid": "Beaud-Flavien" }, { "family_name": "Aati", "given_name": "Saif", "orcid": "0000-0003-1087-832X", "clpid": "Aati-Saif" }, { "family_name": "Delaney", "given_name": "Ian", "orcid": "0000-0003-1722-0600", "clpid": "Delaney-Ian" }, { "family_name": "Adhikari", "given_name": "Surendra", "orcid": "0000-0003-1021-6860", "clpid": "Adhikari-Surendra" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Understanding fast ice flow is key to assessing the future of glaciers. Fast ice flow is controlled by sliding at the bed, yet that sliding is poorly understood. A growing number of studies show the relationship between sliding and basal shear stress transitions from an initially rate-strengthening behavior to a rate-independent or rate-weakening behavior. Studies that have tested a glacier sliding law with data remain rare. Surging glaciers, as we show in this study, can be used as a natural laboratory to inform sliding laws because a single glacier shows extreme velocity variations at a subannual timescale. The present study has two main goals: (1) we introduce a new workflow to produce velocity maps with a high spatiotemporal resolution from remote-sensing data, combining Sentinel-2 (S2) and Landsat 8 (L8) and using the results to describe the recent surge of Shisper Glacier, and (2) we present a generalized sliding law and substantiate the sliding-law behavior using the remote sensing dataset. The quality and spatiotemporal resolution of the velocity time series allow us to identify a gradual amplification of spring speed-up velocities in the 2 years leading up to the surge that started in November 2017. We also find that surface velocity patterns during the surge can be decomposed into three main phases, and each phase appears to be associated with hydraulic changes. Using this dataset, we are able to highlight the rate-independent and rate-weakening relationships between resistive stress and sliding during the surge. We then discuss the importance of the generalized sliding relationship to reconcile observations of fast ice flow, and in particular, different surge behaviors. The approach used in this study remains qualitative, but if coupled with better bed-elevation data and numerical modeling could lead to the widespread quantification of sliding-law parameters.
", "doi": "10.5194/tc-16-3123-2022", "issn": "1994-0424", "publisher": "European Geosciences Union", "publication": "The Cryosphere", "publication_date": "2022-08-03", "series_number": "8", "volume": "16", "issue": "8", "pages": "3123-3148" }, { "id": "authors:7js3m-zsj07", "collection": "authors", "collection_id": "7js3m-zsj07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220614-568568000", "type": "article", "title": "A new approach for 2-D and 3-D precise measurements of ground deformation from optimized registration and correlation of optical images and ICA-based filtering of image geometry artifacts", "author": [ { "family_name": "Aati", "given_name": "Saif", "orcid": "0000-0003-1087-832X", "clpid": "Aati-Saif" }, { "family_name": "Milliner", "given_name": "Chris", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Christopher-W-D" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "High resolution satellite images with improved spatial and temporal resolution provide unprecedented opportunities to monitor Earth Surface changes in 2D and 3D due, for example, to earthquakes, sand dune migration, ice flow, or landslides. The volume of imagery available for such measurements is rapidly growing but the exploitation of these data is challenging due to the various sources of geometric distortions of the satellite imagery. Here we propose a new approach to extract high-quality surface displacement in 3D based on the correlation of multi-date and multi-platform high resolution optical imagery. We additionally show that when a large enough volume of data is available, it is possible to separate the deformation signal from the artifacts due to the satellite jitter and misalignment of the CCDs, which, together with topographic artifacts, are the main source of noise in the measurements. Our method makes use of a reference DEM, but the outcome is independent of the characteristics of the chosen DEM. We use the case-example of the ground deformation caused by the Ridgecrest earthquake sequence to assess the performance of our proposed approach. We show that it outperforms the more standard approach which combines 2-D correlation and DEM differencing. With our technique, we were able to generate high quality measurements of coseismic ground displacement with GSD of 2.4 m, and uncertainties at the 90% confidence level on the NS, EW and vertical displacement measurements of 0.6 m, 0.7 m, and 0.6 m respectively.", "doi": "10.1016/j.rse.2022.113038", "issn": "0034-4257", "publisher": "Elsevier", "publication": "Remote Sensing of Environment", "publication_date": "2022-08", "volume": "277", "pages": "Art. No. 113038" }, { "id": "authors:102h6-xgs60", "collection": "authors", "collection_id": "102h6-xgs60", "cite_using_url": "https://authors.library.caltech.edu/records/102h6-xgs60", "type": "article", "title": "Multi-year measurements of ripple and dune migration on Mars: Implications for the wind regime and sand transport", "author": [ { "family_name": "Roback", "given_name": "Kevin P.", "orcid": "0000-0001-5209-2873", "clpid": "Roback-Kevin-P" }, { "family_name": "Runyon", "given_name": "Kirby", "orcid": "0000-0001-6361-6548" }, { "family_name": "Newman", "given_name": "Claire", "orcid": "0000-0001-9990-8817" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Aeolian sand dunes are observed across the Martian surface. The arrival of the HiRISE camera on Mars Reconnaissance Orbiter at Mars in 2006 enabled detection of modern-day movement of dunes and ripples from orbit for the first time. Since 2006, HiRISE collected a long timeseries of repeat imagery at a few Martian dune fields. We analyze this timeseries of imagery at two of these dune fields, using COSI-Corr for image registration and correlation, to study the movement and dynamics of dunes and meter-scale ripples at the Nili Patera and Meroe Patera barchan dune fields. We present measurements of whole-dune translational sand fluxes extracted at both dune fields via manual tracking of dune crestlines and slipfaces in HiRISE images. We also present a multi-Mars year timeseries of ripple flux measurements. Ripple migration shows a consistent pattern of seasonal variation, with maxima in flux during northern-hemisphere autumn and winter at both dune fields. Ripple migration is also observed to decrease away from the upwind margins of dune fields. We compare our observations with predicted sand transport using winds output from the MarsWRF atmospheric circulation model and theories of sand motion. The model predicts half-hourly, mesoscale winds, from which we estimate the 1 Hz, local-scale winds by assuming a Weibull distribution of wind speed, with parameters chosen based on landed wind data. This approach uses remote sensing observations of bedform migration, and comparisons with model output, to place constraints on the wind regime. Our measurements of the seasonal pattern of sand flux variation agree, to first order, with predictions based on modeled wind speeds. Comparison of the magnitudes of predicted and observed sand fluxes is not feasible due to the high uncertainties in our calculated sand fluxes caused by uncertainties in input parameters, most importantly the assumed fluid threshold for sand transport. However, we note that model predictions fit our observed sand fluxes best when relatively low values of the fluid threshold shear velocity of ~0.6–0.8 m/s (or shear stresses of O(10−3) Pa) are assumed.
", "doi": "10.1016/j.icarus.2022.114966", "issn": "0019-1035", "publisher": "Elsevier", "publication": "Icarus", "publication_date": "2022-07-01", "volume": "380", "pages": "114966" }, { "id": "authors:py16w-tp603", "collection": "authors", "collection_id": "py16w-tp603", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220309-676473000", "type": "article", "title": "Subduction earthquake sequences in a non-linear visco-elasto-plastic megathrust", "author": [ { "family_name": "Dal\u00a0Zilio", "given_name": "Luca", "orcid": "0000-0002-5642-0894", "clpid": "Dal-Zilio-Luca" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Gerya", "given_name": "Taras", "orcid": "0000-0002-1062-2722", "clpid": "Gerya-Taras" } ], "abstract": "We present a 2-D thermomechanical computational framework for simulating earthquake sequences in a non-linear visco-elasto-plastic compressible medium. The method is developed for a plane-strain problem and incorporates an invariant formulation of the classical rate- and state-dependent friction law and an adaptive time-stepping, which allows the time step to vary by many orders of magnitude during a simulation. Long-term tectonic convergence is imposed by displacing a boundary at a constant rate, whereas temperature-dependent viscosity is solved using a rapidly converging Newton\u2013Raphson scheme. The 2-D volume is discretized using finite differences on a fully staggered grid and marker-in-cell techniques. An adaptive free-surface approximation is used to modulate the air viscosity with the time step, which allows stresses to vanish on the free surface during the propagation of fast slipping events. We present a set of increasingly complex models in which we investigate how inertia, radiation damping, thermally activated non-linear rheology and off-megathrust splay-fault events affect sequences of seismic and aseismic slip on a simplified subduction megathrust. The new method provides a unique computational framework to analyse earthquake sequences and to connect forearc deformation with the dynamic properties of the megathrust, thus providing a physical link between observations spanning from slow interseismic strain accumulation to localized coseismic slip of individual earthquakes and post-seismic viscoelastic relaxation.", "doi": "10.1093/gji/ggab521", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2022-05", "series_number": "2", "volume": "229", "issue": "2", "pages": "1098-1121" }, { "id": "authors:csgb4-pzm69", "collection": "authors", "collection_id": "csgb4-pzm69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211012-211827889", "type": "article", "title": "Understanding the Geodetic Signature of Large Aquifer Systems: Example of the Ozark Plateaus in Central United States", "author": [ { "family_name": "Larochelle", "given_name": "Stacy", "orcid": "0000-0001-6161-5605", "clpid": "Larochelle-Stacy" }, { "family_name": "Chanard", "given_name": "Kristel", "orcid": "0000-0001-9934-9621", "clpid": "Chanard-Kristel" }, { "family_name": "Fleitout", "given_name": "Luce", "orcid": "0000-0003-1114-3616", "clpid": "Fleitout-Luce" }, { "family_name": "Fortin", "given_name": "J\u00e9r\u00f4me", "orcid": "0000-0002-6341-3318", "clpid": "Fortin-J\u00e9r\u00f4me-Nicolas" }, { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-Adriano" }, { "family_name": "Longuevergne", "given_name": "Laurent", "orcid": "0000-0003-3169-743X", "clpid": "Longuevergne-Laurent" }, { "family_name": "Rebischung", "given_name": "Paul", "orcid": "0000-0002-2462-1886", "clpid": "Rebischung-Paul" }, { "family_name": "Violette", "given_name": "Sophie", "orcid": "0000-0002-3031-2852", "clpid": "Violette-Sophie" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The continuous redistribution of water involved in the hydrologic cycle leads to deformation of the solid Earth. On a global scale, this deformation is well explained by the loading imposed by hydrological mass variations and can be quantified to first order with space-based gravimetric and geodetic measurements. At the regional scale, however, aquifer systems also undergo poroelastic deformation in response to groundwater fluctuations. Disentangling these related but distinct 3D deformation fields from geodetic time series is essential to accurately invert for changes in continental water mass, to understand the mechanical response of aquifers to internal pressure changes as well as to correct time series for these known effects. Here, we demonstrate a methodology to accomplish this task by considering the example of the well-instrumented Ozark Plateaus Aquifer System (OPAS) in the central United States. We begin by characterizing the most important sources of groundwater level variations in the spatially heterogeneous piezometer dataset using an Independent Component Analysis. Then, to estimate the associated poroelastic displacements, we project geodetic time series corrected for hydrological loading effects onto the dominant groundwater temporal functions. We interpret the extracted displacements in light of analytical solutions and a 2D model relating groundwater level variations to surface displacements. In particular, the relatively low estimates of elastic moduli inferred from the poroelastic displacements and groundwater fluctuations may be indicative of aquifer layers with a high fracture density. Our findings suggest that OPAS undergoes significant poroelastic deformation, including highly heterogeneous horizontal poroelastic displacements.", "doi": "10.1029/2021JB023097", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2022-03", "series_number": "3", "volume": "127", "issue": "3", "pages": "Art. No. e2021JB023097" }, { "id": "authors:r88sx-8tw05", "collection": "authors", "collection_id": "r88sx-8tw05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220414-27838000", "type": "article", "title": "Coulomb threshold rate-and-state model for fault reactivation: application to induced seismicity at Groningen", "author": [ { "family_name": "Heimisson", "given_name": "El\u00edas R.", "orcid": "0000-0001-8342-7226", "clpid": "Heimisson-El\u00edas-R" }, { "family_name": "Smith", "given_name": "Jonathan D.", "orcid": "0000-0002-1684-1344", "clpid": "Smith-Jonathan-D" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bourne", "given_name": "Stephen J.", "orcid": "0000-0003-2925-8411", "clpid": "Bourne-Stephen-J" } ], "abstract": "A number of recent modelling studies of induced seismicity have used the 1994 rate-and-state friction model of Dieterich 1994 to account for the fact that earthquake nucleation is not instantaneous. Notably, the model assumes a population of seismic sources accelerating towards instability with a distribution of initial slip speeds such that they would produce earthquakes steadily in the absence of any perturbation to the system. This assumption may not be valid in typical intraplate settings where most examples of induced seismicity occur, since these regions have low stressing rates and initially low seismic activity. The goal of this paper is twofold. First, to derive a revised Coulomb rate-and-state model, which takes into account that seismic sources can be initially far from instability. Second, to apply and test this new model, called the Threshold rate-and-state model, on the induced seismicity of the Groningen gas field in the Netherlands. Stress changes are calculated based on a model of reservoir compaction since the onset of gas production. We next compare the seismicity predicted by our threshold model and Dieterich's model with the observations. The two models yields comparable spatial distributions of earthquakes in good agreement with the observations. We find however that the Threshold model provides a better fit to the observed time-varying seismicity rate than Dieterich's model, and reproduces better the onset, peak and decline of the observed seismicity rate. We compute the maximum magnitude expected for each model given the Gutenberg\u2013Richter distribution and compare to the observations. We find that the Threshold model both shows better agreement with the observed maximum magnitude and provides result consistent with lack of observed seismicity prior to 1993. We carry out analysis of the model fit using a Chi-squared reduced statistics and find that the model fit is dramatically improved by smoothing the seismicity rate. We interpret this finding as possibly suggesting an influence of source interactions, or clustering, on a long timescale of about 3\u20135 yr.", "doi": "10.1093/gji/ggab467", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2022-03", "series_number": "3", "volume": "228", "issue": "3", "pages": "2061-2072" }, { "id": "authors:3k2tp-eds16", "collection": "authors", "collection_id": "3k2tp-eds16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220120-890583000", "type": "article", "title": "The 2021 Mw 7.4 Madoi Earthquake: An Archetype Bilateral Slip-Pulse Rupture Arrested at a Splay Fault", "author": [ { "family_name": "Chen", "given_name": "Kejie", "orcid": "0000-0002-8878-1731", "clpid": "Chen-Kejie" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Geng", "given_name": "Jianghui", "orcid": "0000-0002-8776-5801", "clpid": "Geng-Jianghui" }, { "family_name": "Liang", "given_name": "Cunren", "orcid": "0000-0003-3938-426X", "clpid": "Liang-Cunren" }, { "family_name": "Zhang", "given_name": "Zhenguo", "orcid": "0000-0002-0059-1766", "clpid": "Zhang-Zhenguo" }, { "family_name": "Li", "given_name": "Zhicai", "clpid": "Li-Zhicai" }, { "family_name": "Zhang", "given_name": "Shengpeng", "clpid": "Zhang-Shengpeng" } ], "abstract": "We combine measurements of ground deformation from Synthetic Aperture Radar images, high-rate Global Navigation Satellite System and tele-seismic waveforms to study the rupture kinematics of the Madoi Earthquake, which occurred in eastern Tibet on 21 May 2021 and reached a moment magnitude M_w 7.4. The data show nearly pure left-lateral motion along a 170 km long rupture and a total duration of 36 s. The earthquake initiated near the middle of the main segment and evolved in a bilateral slip pulse rupture which propagated at a sub-Rayleigh speed of 2.6\u20132.8 km/s. In our model, slip is concentrated at depth of less than \u223c15 km and reaches a maximum of 4.2 m. The rupture arrested \u223c10 s after branching on the extensional splay faults at both extremities. The branching onto the splay faults and the eventual arrest of the rupture is used to provide constraints on the fault frictional properties.", "doi": "10.1029/2021gl095243", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2022-01-28", "series_number": "2", "volume": "49", "issue": "2", "pages": "Art. No. e2021GL095243" }, { "id": "authors:rw7vd-v4b84", "collection": "authors", "collection_id": "rw7vd-v4b84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211025-190753665", "type": "article", "title": "Tectonic tremor as friction-induced inertial vibration", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Slow slip events are often accompanied by tremor but how tremor is generated is yet elusive. In this study, we test the possibility that it is an inertial vibration. In the case of a single-degree-of-freedom spring and slider system with mass per unit area M, governed by rate-and-state friction with effective normal stress \u03c3\u2032, excitation of inertial vibrations emerges when normal stress (\u03c3\u2032) is low, and loading rate (V_l) is high. Accordingly, tremor can be excited in a low effective normal stress (\u03c3\u2032) zone, for example, in a zone of high pore pressure, when the loading rate (V_l) is temporally increased, as can happen during a slow slip event. A high loading rate helps to sustain the vibration, but a long-lasting attenuating tremor can still be excited even with a moderate velocity perturbation as long as the normal stress is sufficiently small. We use numerical simulations to verify that this hypothesis holds for a one-dimensional fault. The dominant frequency of the tremor is close to the fundamental frequency of resonance of the frictionless shear crack at a low sliding rate. Higher frequency modes are excited at higher sliding velocity. We show simulations of spontaneous slow slip events associated with tremor radiated from inertial vibration of a fault patch with locally low effective normal stress. This model provides a possible explanation for tectonic tremor associated with slow slip events.", "doi": "10.1016/j.epsl.2021.117238", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2021-12-15", "volume": "576", "pages": "Art. No. 117238" }, { "id": "authors:ecjyf-zgq10", "collection": "authors", "collection_id": "ecjyf-zgq10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210908-171122066", "type": "article", "title": "On the role of thermal stress and fluid pressure in triggering seismic and aseismic faulting at the Brawley Geothermal Field, California", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Surface deformation and earthquake swarms are correlated in space and time with operations at the Brawley geothermal field in southern California. The seismicity culminated in 2012, about 2 years after the onset of geothermal activity, with a M5.4 earthquake. These earthquakes occurred at a >5km depth, much larger than the \u223c1km reach of the geothermal wells, raising questions about the triggering mechanism. Surface deformation shows that aseismic slip on a normal fault intersecting the geothermal reservoir preceded the swarm and possibly triggered it. In this study, we resort to geomechanical modeling to investigate how the sequence of aseismic and seismic slip unfolded. The modeling accounts for thermo- and poro-elastic stress changes induced by the geothermal operations and allows for inelastic deformation and faulting of the reservoir and surrounding medium. The simulation successfully reproduces the flow rates and well-head pressures reported by the operator as well as the measured surface subsidence. By varying the model parameters, we show that the surface subsidence is due to thermal contraction and normal faulting. The fault reactivation is driven by pressure changes and thermal unclamping. The pressure-driven reactivation is rapid and influences a larger area, while the temperature-driven reactivation is more gradual and more localized near the injection wells. In our simulation, aseismic normal faulting driven by the geothermal operation leads to elastic stress release via yielding and faulting within the reservoir volume and, conversely, to stress build-up beneath the reservoir, where the 2012 swarm developed. Such a stress transfer provides a plausible explanation for the 2012 Brawley swarm. Our study shows how a geothermal operation can, in principle, contribute to seismic hazard mitigation through the aseismic release of tectonic stresses within a geothermal field but points to the difficulty of mitigating the hazard posed by stress transfers in the surrounding area.", "doi": "10.1016/j.geothermics.2021.102238", "issn": "0375-6505", "publisher": "Elsevier", "publication": "Geothermics", "publication_date": "2021-12", "volume": "97", "pages": "Art. No. 102238" }, { "id": "authors:pt8w1-p2c70", "collection": "authors", "collection_id": "pt8w1-p2c70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211001-223725087", "type": "article", "title": "Surface Deformation and Seismicity Induced by Poroelastic Stress at the Raft River Geothermal Field, Idaho, USA", "author": [ { "family_name": "Li", "given_name": "Bing Q.", "orcid": "0000-0002-4158-4941", "clpid": "Li-Bing-Qiuyi" }, { "family_name": "Khoshmanesh", "given_name": "Mostafa", "orcid": "0000-0001-8724-5737", "clpid": "Khoshmanesh-Mostafa" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We investigate the relative importance of injection and production on the spatial-temporal distribution of induced seismicity at the Raft River geothermal field. We use time-series of InSAR measurements to document surface deformation and calibrate a hydro-mechanical model to estimate effective stress changes imparted by injection and production. Seismicity, located predominantly in the basement, is induced primarily by poroelastic stresses from cold water reinjection into a shallower reservoir. The poroelastic effect of production from a deeper reservoir is minimal and inconsistent with observed seismicity, as is pore-pressure-diffusion in the basement and along reactivated faults. We estimate an initial strength excess of \u223c20 kPa in the basement and sedimentary cover, but the seismicity rate in the sedimentary cover is four times lower, reflecting lower density of seed-points for earthquake nucleation. Our modeling workflow could be used to assess the impact of fluid extraction or injection on seismicity and help design or guide operations.", "doi": "10.1029/2021gl095108", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2021-09-20", "series_number": "18", "volume": "48", "issue": "18", "pages": "Art. No. e2021GL095108" }, { "id": "authors:mvcyg-09z46", "collection": "authors", "collection_id": "mvcyg-09z46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210823-154808915", "type": "article", "title": "Inferring Airflow Across Martian Dunes From Ripple Patterns and Dynamics", "author": [ { "family_name": "Hood", "given_name": "D. R.", "orcid": "0000-0002-4137-8208", "clpid": "Hood-Don-R" }, { "family_name": "Ewing", "given_name": "R. C.", "orcid": "0000-0001-6337-610X", "clpid": "Ewing-Ryan-C" }, { "family_name": "Roback", "given_name": "K. P.", "orcid": "0000-0001-5209-2873", "clpid": "Roback-Kevin-P" }, { "family_name": "Runyon", "given_name": "K.", "orcid": "0000-0001-6361-6548", "clpid": "Runyon-Kirby-D" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "McEnroe", "given_name": "M.", "clpid": "McEnroe-M" } ], "abstract": "Large ripples form striking patterns on the slopes of martian sand dunes which can be mapped and tracked using high-resolution optical images. The ripples vary in orientation, wavelength, plan-view morphology, and rates of migration. The variations in the ripple patterns are recognized to signal the effects of the regional and local winds and feedbacks between winds and dune topography. We examine the ripple patterns and the motion of these ripples to interpret airflow dynamics around dunes in the dune field at Nili Patera. We find that coincident changes in ripple patterns and migration rates in dune wakes indicate reattachment lengths of 4\u20137 brink heights. This reattachment length is similar to length scales of flow reattachment for airflow over dunes measured on Earth despite the differences in aeolian environment. Furthermore, ripples on dune flanks are shown to behave according to terrestrial models for ripple development on steep slopes. Compensating for these slope effects allows them to act as indicators of dune-modified and regional wind directions. Changes in ripple patterns and migration rates also signal the response of dunes and airflow during dune collisions. Collectively, we find that differences in ripple patterns connected to changes in migration rate provide information on airflow over and around dunes. This detailed assessment of ripple measurement and ripple migration rates advances the use of ripples on martian dunes and sand sheets to infer dune- and field-scale wind dynamics. These measurements also indicate that the low density atmosphere on Mars does not significantly modify the behavior of wind-topography interactions compared to Earth. Such observations provide targets for computational fluid dynamic and large-eddy simulation models seeking to reveal complex airflows across dune fields both on Earth and on Mars.", "doi": "10.3389/feart.2021.702828", "issn": "2296-6463", "publisher": "Frontiers Media SA", "publication": "Frontiers in Earth Science", "publication_date": "2021-07-12", "volume": "9", "pages": "Art. No. 702828" }, { "id": "authors:n1n6t-pxs56", "collection": "authors", "collection_id": "n1n6t-pxs56", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210426-094559595", "type": "article", "title": "Ridgecrest aftershocks at Coso suppressed by thermal destressing", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Heimisson", "given_name": "El\u00edas R.", "orcid": "0000-0001-8342-7226", "clpid": "Heimisson-El\u00edas-R" }, { "family_name": "Elsworth", "given_name": "Derek", "orcid": "0000-0002-4942-1151", "clpid": "Elsworth-Derek" } ], "abstract": "Geothermal and volcanic areas are prone to earthquake triggering. The Coso geothermal field in California lies just north of the surface ruptures driven by the 2019 Ridgecrest earthquake (moment magnitude M_w = 7.1), in an area where changes in coseismic stress should have triggered aftershocks. However, no aftershocks were observed there. Here we show that 30 years of geothermal heat production at Coso depleted shear stresses within the geothermal reservoir. Thermal contraction of the reservoir initially induced substantial seismicity, as observed in the Coso geothermal reservoir, but subsequently depleted the stress available to drive the aftershocks during the Ridgecrest sequence. This destressing changed the faulting style of the reservoir and impeded aftershock triggering. Although unlikely to have been the case for the Ridgecrest earthquake, such a destressed zone could, in principle, impede the propagation of a large earthquake.", "doi": "10.1038/s41586-021-03601-4", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2021-07-01", "series_number": "7865", "volume": "595", "issue": "7865", "pages": "70-74" }, { "id": "authors:zty5n-mg039", "collection": "authors", "collection_id": "zty5n-mg039", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210910-231037057", "type": "article", "title": "On the relationship between strain rate and seismicity in the India\u2013Asia collision zone: implications for probabilistic seismic hazard", "author": [ { "family_name": "Stevens", "given_name": "V. L.", "orcid": "0000-0003-3174-9949", "clpid": "Stevens-Victoria-L" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The increasing density of geodetic measurements makes it possible to map surface strain rate in many zones of active tectonics with unprecedented spatial resolution. Here we show that the strain tensor rate calculated from GPS in the India\u2013Asia collision zone represents well the strain released in earthquakes. This means that geodetic data in the India\u2013Asia collision zone region can be extrapolated back in time to estimate strain buildup on active faults, or the kinematics of continental deformation. We infer that the geodetic strain rates can be assumed stationary through time on the timescale needed to build up the elastic strain released by larger earthquakes, and that they can be used to estimate the probability of triggering earthquakes. We show that the background seismicity rate correlates with the geodetic strain rate. A good fit is obtained assuming a linear relationship (\u2060\u02d9N=\u03bb \u22c5\u02d9\u03f5\u2060, where \u02d9N is the density of the rate of M_w \u2265 4 earthquakes, \u02d9\u03f5 is strain rate and \u03bb = 2.5 \u00b1 0.1 \u00d7 10\u207b\u00b3 m\u207b\u00b2), as would be expected from a standard Coulomb failure model. However, the fit is significantly better for a non-linear relationship (\u2060\u02d9N=\u03b3\u2081\u22c5\u02d9\u03f5^(\u03b3\u2082) with \u03b3\u2081 = 2.5 \u00b1 0.6 m\u207b\u00b2 and \u03b3\u2082 = 1.42 \u00b1 0.15). The b-value of the Gutenberg\u2013Richter law, which characterize the magnitude\u2013frequency distribution, is found to be insensitive to the strain rate. In the case of a linear correlation between seismicity and strain rate, the maximum magnitude earthquake, derived from the moment conservation principle, is expected to be independent of the strain rate. By contrast, the non-linear case implies that the maximum magnitude earthquake would be larger in zones of low strain rate. We show that within areas of constant strain rate, earthquakes above M_w 4 follow a Poisson distribution in time and and are uniformly distributed in space. These findings provide a framework to estimate the probability of occurrence and magnitude of earthquakes as a function of the geodetic strain rate. We describe how the seismicity models derived from this approach can be used as an input for probabilistic seismic hazard analysis. This method is easy to automatically update, and can be applied in a consistent manner to any continental zone of active tectonics with sufficient geodetic coverage.", "doi": "10.1093/gji/ggab098", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2021-07", "series_number": "1", "volume": "226", "issue": "1", "pages": "220-245" }, { "id": "authors:qabts-rck83", "collection": "authors", "collection_id": "qabts-rck83", "cite_using_url": "https://authors.library.caltech.edu/records/qabts-rck83", "type": "article", "title": "Bookshelf Kinematics and the Effect of Dilatation on Fault Zone Inelastic Deformation: Examples From Optical Image Correlation Measurements of the 2019 Ridgecrest Earthquake Sequence", "author": [ { "family_name": "Milliner", "given_name": "Christopher", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-Christopher" }, { "family_name": "Donnellan", "given_name": "Andrea", "orcid": "0000-0001-6843-8373", "clpid": "Donnellan-Andrea" }, { "family_name": "Aati", "given_name": "Saif", "orcid": "0000-0003-1087-832X", "clpid": "Aati-Saif" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Zinke", "given_name": "Robert", "orcid": "0000-0003-4174-3137", "clpid": "Zinke-Robert" }, { "family_name": "Dolan", "given_name": "James F.", "orcid": "0000-0002-6799-5781" }, { "family_name": "Wang", "given_name": "Kang", "orcid": "0000-0002-9725-3295" }, { "family_name": "B\u00fcrgmann", "given_name": "Roland", "orcid": "0000-0002-3560-044X" } ], "abstract": "The 2019 Ridgecrest earthquake sequence initiated on July 4th with a series of foreshocks, including an Mw 6.4 event, that culminated a day later with the Mw 7.1 mainshock and resulted in rupture of a set of cross-faults. In this study, we use subpixel correlation of optical satellite imagery to measure the displacement, finite strain, and rotation of the near-field coseismic deformation to understand the kinematics of strain release along the surface ruptures. We find the average off-fault deformation along the mainshock rupture is 34% and is significantly higher along the foreshock rupture (56%), suggesting it is a less structurally developed fault system. Measurements of the 2D dilatational strain along the mainshock rupture show a dependency of the width of inelastic strain with the degree of fault extension and contraction, indicating wider fault zones under extension than under shear. Measurements of the vorticity along the main, dextral rupture show that conjugate sinistral faults are embedded within zones of large clockwise rotations caused by the transition of strain beyond the tips of dextral faults leading to bookshelf kinematics. These rotations and bookshelf slip can explain why faults of different shear senses do not intersect one another and the occurrence of pervasive and mechanically unfavorable cross-faulting in this region. Understanding the causes for the variation of fault zone widths along surface ruptures has importance for reducing the epistemic uncertainty of probabilistic models of distributed rupture that will, in turn, provide more precise estimates of the hazard distributed rupture poses to nearby infrastructure.
", "doi": "10.1029/2020jb020551", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research: Solid Earth", "publication_date": "2021-03", "series_number": "3", "volume": "126", "issue": "3", "pages": "e2020JB020551" }, { "id": "authors:d5p5p-a7328", "collection": "authors", "collection_id": "d5p5p-a7328", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201123-125242998", "type": "article", "title": "Analytical prediction of seismicity rate due to tides and other oscillating stresses", "author": [ { "family_name": "Heimisson", "given_name": "El\u00edas R.", "orcid": "0000-0001-8342-7226", "clpid": "Heimisson-Elias-R" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Oscillatory stresses are ubiquitous on Earth and other solid\u2010surface bodies. Tides and seasonal signals perpetually stress faults in the crust. Relating seismicity to these stresses offers fundamental insight into earthquake triggering. We present a simple model that describes seismicity rate due to perpetual oscillatory stresses. The model applies to large\u2010amplitude, nonharmonic, and quasiperiodic stressing. However, it is not valid for periods similar to the characteristic time ta. We show that seismicity rate from short\u2010period stressing scales with the stress amplitude, but for long periods with the stressing rate. Further, that background seismicity rate r is equal to the average seismicity rate during short\u2010period stressing. We suggest that A\u03c3\u2080 may be underestimated if stresses are approximated by a single harmonic function. We revisit Manga et al. (2019, https://doi.org/10.1029/2019GL082892), which analyzed the tidal triggering of marsquakes and provide a rescaling of their seismicity rate response that offers a self\u2010consistent comparison of different hydraulic conditions.", "doi": "10.1029/2020gl090827", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2020-12-16", "series_number": "23", "volume": "47", "issue": "23", "pages": "Art. No. e2020GL090827" }, { "id": "authors:f1yym-dba59", "collection": "authors", "collection_id": "f1yym-dba59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201021-145702533", "type": "article", "title": "Optimization of Optical Image Geometric Modeling, Application to Topography Extraction and Topographic Change Measurements Using PlanetScope and SkySat Imagery", "author": [ { "family_name": "Aati", "given_name": "Saif", "orcid": "0000-0003-1087-832X", "clpid": "Aati-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The volume of data generated by earth observation satellites has increased tremendously over the last few decades and will increase further in the coming decade thanks in particular to the launch of nanosatellites constellations. These data should open new avenues for Earth surface monitoring due to highly improved spectral, spatial and temporal resolution. Many applications depend, however, on the accuracy of the image geometric model. The geometry of optical images, whether acquired from pushbroom or frame systems, is now commonly represented using a Rational Function Model (RFM). While the formalism has become standard, the procedures used to generate these models and their accuracies are diverse. As a result, the RFM models delivered with commercial data are commonly not accurate enough for 3-D extraction, subpixel registration or ground deformation measurements. In this study, we present a methodology for RFM optimization and demonstrate its potential for 3D reconstruction using tri-stereo and multi-date Cubesat images provided by SkySat and PlanetScope, respectively. We use SkySat data over the Morenci Mine, Arizona, which is the largest copper mine in the United States. The re-projection error after the RFM refinement is 0.42 pix without using ground control points (GCPs). Comparison of our Digital Elevation Model (DEM with ~3 m GSD) with a reference DEM obtained from an airborne LiDAR survey (with ~1 m GSD) over stable areas yields a standard deviation of the elevation differences of ~3.9 m. The comparison of the two DEMs allows detecting and measuring the topographic changes due to the mine activity (excavation and stockpiles). We assess the potential of PlanetScope data, using multi-date DOVE-C images from the Shisper glacier, located in the Karakoram (Pakistan), which is known for its recent surge. We extracted DEMs in 2017 and 2019 before and after the surge. The re-projection error after the RFM refinement is 0.38 pix without using GCPs. The accuracy of our DEMs (with ~9 m GSD) is evaluated through comparison with the SRTM DEM (GSD ~30 m) and with a DEM (GSD ~2 m) calculated from Geoeye-1 (GE-1) and World-View-2 (WV-2) stereo images. The standard deviation of the elevation differences in stable areas between the PlanetScope DEM and SRTM is ~12 m, and ~7 m with the GE-1&WV-2 DEM. The mass transfer due to the surge is clearly revealed from a comparison of the 2017 and 2019 DEMs. The study demonstrates that, with the proposed scheme for RFM optimization, times series of DEM extracted from SkySat and PlanetScope images can be used to measure topographic changes due to mining activities or ice flow, and could also be used to monitor geomorphic processes such as landslides, or coastal erosion for example.", "doi": "10.3390/rs12203418", "issn": "2072-4292", "publisher": "MDPI", "publication": "Remote Sensing", "publication_date": "2020-10-19", "series_number": "20", "volume": "12", "issue": "20", "pages": "Art. No. 3418" }, { "id": "authors:wfg20-4tn76", "collection": "authors", "collection_id": "wfg20-4tn76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201014-131627239", "type": "article", "title": "Structural Evolution of Orogenic Wedges: Interplay Between Erosion and Weak D\u00e9collements", "author": [ { "family_name": "Dal Zilio", "given_name": "Luca", "orcid": "0000-0002-5642-0894", "clpid": "Dal-Zilio-Luca" }, { "family_name": "Ruh", "given_name": "Jonas", "orcid": "0000-0001-7035-1453", "clpid": "Ruh-Jonas" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Orogenic wedges commonly display an inner wedge, where crystalline units have been exhumed, and an outer wedge formed by imbricated sedimentary units detached from the basement. Analog experiments have shown that similar structures can emerge naturally in the presence of weak d\u00e9collements due to the interplay between erosion and deformation. In this study, we further investigate this hypothesis using two\u2010dimensional, visco\u2010elasto\u2010plastic numerical models. Our experiments assume a basal and an intermediate d\u00e9collement within the wedge. Experiments with a frictional strength of the basal d\u00e9collement lower or equal to that of the intermediate d\u00e9collement show a structural evolution of fold\u2010and\u2010thrust belts dominated by out\u2010of\u2010sequence thrusting. Conversely, when the intermediate d\u00e9collement is weaker than the basal d\u00e9collement, distinct outer and inner wedges are formed. This process leads to episodic migration of midcrustal ramps, tectonic underplating, and antiformal stacking facilitated by erosion. Comparison between our models and the Himalayan wedge suggests a low effective friction (\u223c0.10), which is probably due to dynamic weakening during large (M8+) Himalayan earthquakes. The deeper d\u00e9collement, along which the lower plate thrusts beneath the High Himalaya, must be a thermally activated ductile shear zone with an apparent friction of \u223c0.18. Fold\u2010and\u2010thrust belts worldwide exhibit various architectures in which different d\u00e9collement levels might be activated. Thus, our study provides a framework to help assess under which conditions a variety of structures observed in orogenic systems can arise.", "doi": "10.1029/2020tc006210", "issn": "0278-7407", "publisher": "American Geophysical Union", "publication": "Tectonics", "publication_date": "2020-10", "series_number": "10", "volume": "39", "issue": "10", "pages": "Art. No. e2020TC006210" }, { "id": "authors:750xa-xag63", "collection": "authors", "collection_id": "750xa-xag63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200722-143843550", "type": "article", "title": "Slip-rate-dependent friction as a universal mechanism for slow slip events", "author": [ { "family_name": "Im", "given_name": "Kyungjae", "orcid": "0000-0003-0057-3119", "clpid": "Im-Kyungjae" }, { "family_name": "Saffer", "given_name": "Demian", "orcid": "0000-0003-3681-0040", "clpid": "Saffer-D" }, { "family_name": "Marone", "given_name": "Chris", "clpid": "Marone-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "A growing body of observations worldwide has documented fault slip transients that radiate little or no seismic energy. The mechanisms that govern these slow slip events (SSEs) and their wide range of depths, slip rates, durations, stress drops and recurrence intervals remain poorly known. Here we show that slow slip can be explained by a transition from rate-weakening frictional sliding at low slip rates towards rate-neutral or rate-strengthening behaviour at higher slip rates, as has been observed experimentally. We use numerical simulations to illustrate that this rate-dependent transition quantitatively explains the experimental data for natural fault rocks representative of materials in the source regions of SSEs. With a standard constant-parameter rate-and-state friction law, SSEs arise only near the threshold for slip instability. The inclusion of velocity-dependent friction parameters substantially broadens the range of conditions for slow slip occurrence, and produces a wide range of event characteristics, which include stress drop, duration and recurrence, as observed in nature. Upscaled numerical simulations that incorporate parameters consistent with laboratory measurements can reproduce geodetic observations of repeating SSEs on tectonic faults. We conclude that slip-rate-dependent friction explains the ubiquitous occurrence of SSEs in a broad range of geological environments.", "doi": "10.1038/s41561-020-0627-9", "issn": "1752-0894", "publisher": "Nature Publishing Group", "publication": "Nature Geoscience", "publication_date": "2020-10", "volume": "13", "pages": "705-710" }, { "id": "authors:8tctn-xb629", "collection": "authors", "collection_id": "8tctn-xb629", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200819-162804555", "type": "article", "title": "Postseismic Deformation Following the 2015 M_w7.8 Gorkha (Nepal) Earthquake: New GPS Data, Kinematic and Dynamic Models, and the Roles of Afterslip and Viscoelastic Relaxation", "author": [ { "family_name": "Liu-Zeng", "given_name": "J.", "clpid": "Liu-Zeng-J" }, { "family_name": "Zhang", "given_name": "Z.", "clpid": "Zhang-Z" }, { "family_name": "Rollins", "given_name": "C.", "orcid": "0000-0002-5291-6956", "clpid": "Rollins-Christopher" }, { "family_name": "Gualandi", "given_name": "A.", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-Adriano" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Shi", "given_name": "H.", "clpid": "Shi-H" }, { "family_name": "Wang", "given_name": "P.", "clpid": "Wang-P" }, { "family_name": "Chen", "given_name": "W.", "clpid": "Chen-W" }, { "family_name": "Zhang", "given_name": "R.", "clpid": "Zhang-R" }, { "family_name": "Zhang", "given_name": "P.", "clpid": "Zhang-P" }, { "family_name": "Wang", "given_name": "W.", "clpid": "Wang-W" }, { "family_name": "Li", "given_name": "Y.", "clpid": "Li-Y" }, { "family_name": "Wang", "given_name": "T.", "clpid": "Wang-T" }, { "family_name": "Li", "given_name": "Z.", "clpid": "Li-Z" } ], "abstract": "We report Global Positioning System (GPS) measurements of postseismic deformation following the 2015 M_w7.8 Gorkha (Nepal) earthquake, including previously unpublished data from 13 continuous GPS stations installed in southern Tibet shortly after the earthquake. We use variational Bayesian Independent Component Analysis (vbICA) to extract the signal of postseismic deformation from the GPS time series, revealing a broad displacement field extending >150 km northward from the rupture. Kinematic inversions and dynamic forward models show that these displacements could have been produced solely by afterslip on the Main Himalayan Thrust (MHT) but would require a broad distribution of afterslip extending similarly far north. This would require the constitutive parameter (a \u2212 b)\u03c3 to decrease northward on the MHT to \u22640.05 MPa (an extreme sensitivity of creep rate to stress change) and seems unlikely in light of the low interseismic coupling and high midcrustal temperatures beneath southern Tibet. We conclude that the northward reach of postseismic deformation more likely results from distributed viscoelastic relaxation, possibly in a midcrustal shear zone extending northward from the seismogenic MHT. Assuming a shear zone 5\u201320 km thick, we estimate an effective shear\u2010zone viscosity of ~3\u00b710\u00b9\u2076\u20133\u00b710\u00b9\u2077 Pa\u00b7s over the first 1.12 postseismic years. Near\u2010field deformation can be more plausibly explained by afterslip itself and implies (a \u2212 b)\u03c3 ~ 0.5\u20131 MPa, consistent with other afterslip studies. This near\u2010field afterslip by itself would have re\u2010increased the Coulomb stress by \u22650.05 MPa over >30% of the Gorkha rupture zone in the first postseismic year, and deformation further north would have compounded this reloading.", "doi": "10.1029/2020jb019852", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2020-09", "series_number": "9", "volume": "125", "issue": "9", "pages": "Art. No. e2020JB019852" }, { "id": "authors:awvsa-zcc40", "collection": "authors", "collection_id": "awvsa-zcc40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200702-084851713", "type": "article", "title": "The predictable chaos of slow earthquakes", "author": [ { "family_name": "Gualandi", "given_name": "A.", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-A" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Michel", "given_name": "S.", "orcid": "0000-0001-7878-6603", "clpid": "Michel-S" }, { "family_name": "Faranda", "given_name": "D.", "clpid": "Faranda-D" } ], "abstract": "Slow earthquakes, like regular earthquakes, result from unstable frictional slip. They produce little slip and can therefore repeat frequently. We assess their predictability using the slip history of the Cascadia subduction between 2007 and 2017, during which slow earthquakes have repeatedly ruptured multiple segments. We characterize the system dynamics using embedding theory and extreme value theory. The analysis reveals a low-dimensional (<5) nonlinear chaotic system rather than a stochastic system. We calculate properties of the underlying attractor like its correlation and instantaneous dimension, instantaneous persistence, and metric entropy. We infer that the system has a predictability horizon of the order of days weeks. For the better resolved segments, the onset of large slip events can be correctly forecasted by high values of the instantaneous dimension. Longer-term deterministic prediction seems intrinsically impossible. Regular earthquakes might similarly be predictable but with a limited predictable horizon of the order of their durations.", "doi": "10.1126/sciadv.aaz5548", "issn": "2375-2548", "publisher": "American Association for the Advancement of Science", "publication": "Science Advances", "publication_date": "2020-07-01", "series_number": "27", "volume": "6", "issue": "27", "pages": "Art. No. eaaz5548" }, { "id": "authors:gkdje-nds59", "collection": "authors", "collection_id": "gkdje-nds59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200625-112849428", "type": "article", "title": "Probabilistic earthquake locations of induced seismicity in the Groningen region, the Netherlands", "author": [ { "family_name": "Smith", "given_name": "Jonathan D.", "orcid": "0000-0002-1684-1344", "clpid": "Smith-J-D" }, { "family_name": "White", "given_name": "Robert S.", "clpid": "White-R-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bourne", "given_name": "Stephen", "orcid": "0000-0003-2925-8411", "clpid": "Bourne-Stephen" } ], "abstract": "The Groningen gas reservoir, situated in the northeast of the Netherlands, is western Europe's largest producing gas field and has been in production since 1963. The gas production has induced both subsidence and seismicity. Seismicity is detected and located using the Koninklijk Nederlands Meteorologisch Instituut shallow-borehole array for the period 2015\u20132017, incorporating the back projection techniques of QuakeMigrate and the nonlinear location procedure to constrain earthquake locations and depths. The uncertainties on the estimated depths are estimated taking into account velocity model, changes in station array geometry and uncertainties in the measurement of arrival times of the P and S waves. We show that the depth distribution of seismicity is consistent with nucleation within the reservoir (28 per cent) or in the overburden (60 per cent) within \u223c500\u2009m from the top of the reservoir. Earthquakes with hypocentres in the overburden likely originate from overlying Zechstein anhydrite caprock. Based on their depth distribution, it seems like the earthquakes are primarily driven by the elastic strain in the reservoir and overburden, induced by the reservoir compaction. We estimate the probability of earthquakes nucleating beneath the reservoir in the underlying Carboniferous limestone and basement, to be no more than 12 per cent.", "doi": "10.1093/gji/ggaa179", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2020-07-01", "series_number": "1", "volume": "222", "issue": "1", "pages": "507-516" }, { "id": "authors:hcg0j-pk874", "collection": "authors", "collection_id": "hcg0j-pk874", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200513-130033224", "type": "article", "title": "Unraveling scaling properties of slow-slip events", "author": [ { "family_name": "Dal Zilio", "given_name": "Luca", "orcid": "0000-0002-5642-0894", "clpid": "Dal-Zilio-Luca" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "A major debate in geophysics is whether earthquakes and slow\u2010slip events (SSEs) arise from similar failure mechanisms. Recent observations from different subduction zones suggest that SSEs follow the same moment\u2010duration scaling as earthquakes, unlike qualitatively different scaling proposed by earlier studies. Here, we examine the scaling properties using dynamic simulations of frictional sliding. The resulting sequences of SSEs match observations from the Cascadia subduction zone, including the earthquake\u2010like cubic moment\u2010duration scaling. In contrast to conventional and widely used assumptions of magnitude\u2010invariant rupture velocities and stress drops, both simulated and natural SSEs have rupture velocities and stress drops that increase with event magnitudes. These findings support the same frictional origin for both earthquakes and SSEs while suggesting a new explanation for the observed SSEs scaling.", "doi": "10.1029/2020gl087477", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2020-05-28", "series_number": "10", "volume": "47", "issue": "10", "pages": "Art. No. e2020GL087477" }, { "id": "authors:zp8cq-w4h90", "collection": "authors", "collection_id": "zp8cq-w4h90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200115-110847580", "type": "article", "title": "Craters as sand traps: Dynamics, history, and morphology of modern sand transport in an active Martian dune field", "author": [ { "family_name": "Roback", "given_name": "K. P.", "clpid": "Roback-K-P" }, { "family_name": "Runyon", "given_name": "K. D.", "clpid": "Runyon-K-D" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Aeolian transport of sand is abundant on modern-day Mars, as revealed by remote sensing measurements of the motion of dunes, and of the meter-scale ripples that mantle them. We study a large-scale natural sand trap within the Meroe Patera dune field: a 1.8-km diameter crater which features a dune-free \"shadow\" in its lee. We compare the volume of sand trapped within this crater to the sand volume that would be expected to cover the area of the crater and its dune-free shadow behind it if the crater were not present. We find that the crater holds less sand than this \"missing\" volume would predict, implying that sand escapes from the crater over time. Modern day imagery shows an apparent lack of sand escaping from the Meroe crater, however, suggesting that changes in the wind regime at the site may have allowed sand to escape in the past. The persistence of an altered dune morphology all the way to the far downwind edge of the dune field suggests consistent wind conditions over the time of the crater-dune field interaction.", "doi": "10.1016/j.icarus.2020.113642", "issn": "0019-1035", "publisher": "Elsevier", "publication": "Icarus", "publication_date": "2020-05-15", "volume": "342", "pages": "Art. No. 113642" }, { "id": "authors:dx550-nbe80", "collection": "authors", "collection_id": "dx550-nbe80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200213-082142665", "type": "article", "title": "Experimental and modeling study of the effect of fault roughness on dynamic frictional sliding", "author": [ { "family_name": "Tal", "given_name": "Yuval", "orcid": "0000-0001-7308-9294", "clpid": "Tal-Yuval" }, { "family_name": "Goebel", "given_name": "Thomas", "orcid": "0000-0003-1552-0861", "clpid": "Goebel-T" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Friction governs many processes in nature from the motion of glaciers and landslides to tremors and earthquakes. The roughness of the sliding interfaces presumably affects their dynamics, in particular the condition for stable or unstable sliding. We investigate this issue by modeling numerically tri-axial stick-slip experiments on Westerly granite samples with different levels of roughness. The model accounts for surface roughness at the millimeter scale and assumes rate and state friction with enhanced dynamic weakening. It reproduces key characteristics observed in the experiments, such as sequences of fast stick-slip events for smooth surface and sequence of slow slip events with small stress drop followed by a large-stress drop unstable slip event for the rough interface. The increase in loading stiffness due to the additional resistance from roughness can explain the initial slow slip. The fast-unstable event may be the result of the higher critical stiffness due to the increase of local normal tractions with slip, as well as of the reduction of the loading stiffness due to contacts losses. The study allows examining numerically the relationship between the frictional behavior on the interface and the apparent friction estimated from external loads. We find that, because of dynamic overshoot, the reduction in apparent friction is larger than that of the actual friction coefficient on the interface.", "doi": "10.1016/j.epsl.2020.116133", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2020-04-15", "volume": "536", "pages": "Art. No. 116133" }, { "id": "authors:w64dc-mxm20", "collection": "authors", "collection_id": "w64dc-mxm20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200323-083435029", "type": "article", "title": "A warning against over-interpretation of seasonal signals measured by the Global Navigation Satellite System", "author": [ { "family_name": "Chanard", "given_name": "Kristel", "orcid": "0000-0001-9934-9621", "clpid": "Chanard-K" }, { "family_name": "M\u00e9tois", "given_name": "Marianne", "orcid": "0000-0002-1489-0513", "clpid": "M\u00e9tois-M" }, { "family_name": "Rebischung", "given_name": "Paul", "clpid": "Rebischung-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "In a recent study, Panda et al. claim that seasonal strain across the Himalaya indicates seasonal slow slip on the Main Himalayan Thrust (MHT) fault driven by hydrological loading related to the monsoon and driving seasonal variations of seismicity. While we find the analysis interesting, we spell out some reasons why the claim should be considered with caution.", "doi": "10.1038/s41467-020-15100-7", "pmcid": "PMC7070017", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2020-03-13", "volume": "11", "pages": "Art. No. 1375" }, { "id": "authors:p8c77-y8548", "collection": "authors", "collection_id": "p8c77-y8548", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200108-110234385", "type": "article", "title": "Cascading and pulse-like ruptures during the 2019 Ridgecrest earthquakes in the Eastern California Shear Zone", "author": [ { "family_name": "Chen", "given_name": "Kejie", "orcid": "0000-0002-8878-1731", "clpid": "Chen-Kejie" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Aati", "given_name": "Saif", "orcid": "0000-0003-1087-832X", "clpid": "Aati-S" }, { "family_name": "Milliner", "given_name": "Chris", "orcid": "0000-0002-3790-595X", "clpid": "Milliner-C" }, { "family_name": "Zheng", "given_name": "Fu", "clpid": "Zheng-Fu" }, { "family_name": "Shi", "given_name": "Chuang", "clpid": "Shi-Chuang" } ], "abstract": "On July 4 2019, a M_w 6.5 earthquake, followed 34\u2009h later by a M_w 7.1 event, struck Searles Valley, California. These events are part of a long-lived cluster of historical earthquakes along the Eastern California Shear Zone (ECSZ) which started in 1872 and are associated with temporarily elevated strain rates. We find that the M_w 6.5 event initiated on a right-lateral NW striking fault and then ruptured a left-lateral fault to the surface. This event triggered right-lateral slip during the M_w 7.1 earthquake. It started as a bilateral, crack-like rupture on a segment brought closer to failure by the M_w 6.5 event. The rupture evolved to pulse-like as it propagated at a relatively slow velocity (2\u2009km/s) along a segment that was unloaded by the M_w 6.5 event. It stopped abruptly at the Coso volcanic area and at the Garlock Fault and brought some neighbouring faults closer to failure.", "doi": "10.1038/s41467-019-13750-w", "pmcid": "PMC6946662", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2020-01-07", "volume": "11", "pages": "Art. No. 22" }, { "id": "authors:63etc-deb78", "collection": "authors", "collection_id": "63etc-deb78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190801-132601461", "type": "article", "title": "Similar scaling laws for earthquakes and Cascadia slow-slip events", "author": [ { "family_name": "Michel", "given_name": "Sylvain", "orcid": "0000-0001-7878-6603", "clpid": "Michel-S" }, { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Faults can slip not only episodically during earthquakes but also during transient aseismic slip events, often called slow-slip events. Previous studies based on observations compiled from various tectonic settings have suggested that the moment of slow-slip events is proportional to their duration, instead of following the duration-cubed scaling found for earthquakes. This finding has spurred efforts to unravel the cause of the difference in scaling. Thanks to a new catalogue of slow-slip events on the Cascadia megathrust based on the inversion of surface deformation measurements between 2007 and 2017, we find that a cubic moment\u2013duration scaling law is more likely. Like regular earthquakes, slow-slip events also have a moment that is proportional to A^(3/2), where A is the rupture area, and obey the Gutenberg\u2013Richter relationship between frequency and magnitude. Finally, these slow-slip events show pulse-like ruptures similar to seismic ruptures. The scaling properties of slow-slip events are thus strikingly similar to those of regular earthquakes, suggesting that they are governed by similar dynamic properties.", "doi": "10.1038/s41586-019-1673-6", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2019-10-24", "series_number": "7779", "volume": "574", "issue": "7779", "pages": "522-526" }, { "id": "authors:v9pfg-9hy69", "collection": "authors", "collection_id": "v9pfg-9hy69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180924-160011784", "type": "article", "title": "Interseismic Coupling and Slow Slip Events on the Cascadia Megathrust", "author": [ { "family_name": "Michel", "given_name": "Sylvain", "orcid": "0000-0001-7878-6603", "clpid": "Michel-S" }, { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "In this study, we model geodetic strain accumulation along the Cascadia subduction zone between 2007.0 and 2017.632 using position time series from 352 continuous GPS stations. First, we use the secular linear motion to determine interseismic locking along the megathrust. We determine two end member models, assuming that the megathrust is either a priori locked or creeping, which differ essentially along the trench where the inversion is poorly constrained by the data. In either case, significant locking of the megathrust updip of the coastline is needed. The downdip limit of the locked portion lies\u2009\u223c\u200920\u201380 km updip from the coast assuming a locked a priori, but very close to the coast for a creeping a priori. Second, we use a variational Bayesian Independent Component Analysis (vbICA) decomposition to model geodetic strain time variations, an approach which is effective to separate the geodetic strain signal due to non-tectonic and tectonic sources. The Slow Slip Events (SSEs) kinematics is retrieved by linearly inverting for slip on the megathrust the Independent Components related to these transient phenomena. The procedure allows the detection and modelling of 64 SSEs which spatially and temporally match with the tremors activity. SEEs and tremors occur well inland from the coastline and follow closely the estimated location of the mantle wedge corner. The transition zone, between the locked portion of the megathrust and the zone of tremors, is creeping rather steadily at the long-term slip rate and probably buffers the effect of SSEs on the megathrust seismogenic portion.", "doi": "10.1007/s00024-018-1991-x", "issn": "0033-4553", "publisher": "Springer", "publication": "Pure and Applied Geophysics", "publication_date": "2019-09", "series_number": "9", "volume": "176", "issue": "9", "pages": "3867-3891" }, { "id": "authors:bzn86-qm394", "collection": "authors", "collection_id": "bzn86-qm394", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221115-689860300.1", "type": "article", "title": "Reconciling the Long\u2010Term Relationship Between Reservoir Pore Pressure Depletion and Compaction in the Groningen Region", "author": [ { "family_name": "Smith", "given_name": "Jonathan D.", "orcid": "0000-0002-1684-1344", "clpid": "Smith-Jonathan-D" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "White", "given_name": "Robert S.", "orcid": "0000-0002-2972-397X", "clpid": "White-Robert-S" }, { "family_name": "Copley", "given_name": "Alex", "orcid": "0000-0003-0362-0494", "clpid": "Copley-Alex" }, { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-Adriano" }, { "family_name": "Bourne", "given_name": "Stephen", "orcid": "0000-0003-2925-8411", "clpid": "Bourne-Stephen" } ], "abstract": "The Groningen gas reservoir, situated in the northeast of the Netherlands is western Europe's largest gas reservoir. Due to gas production measurable subsidence and seismicity has been detected across this region, attributed to the deformations induced by reservoir pore pressure depletion. We investigate the surface displacement history using a principal component analysis-based inversion method to combine a diverse set of optical leveling, interferometric synthetic aperture radar, and Global Positioning System data to better constrain reservoir compaction and subsidence history. The generated compaction model is then used in combination with prior pressure depletion models to determine a reservoir uniaxial compressibility. The best fitting model of uniaxial compressibility is time independent but spatially variable. The absence of evidence for any significant time delay between changes in depletion and compaction rates supports an instantaneous poroelastic reservoir response. The absence of nonlinear yielding at the largest compaction strains suggests that anelastic deformations are a minor part of reservoir compaction.", "doi": "10.1029/2018jb016801", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2019-06", "series_number": "6", "volume": "124", "issue": "6", "pages": "6165-6178" }, { "id": "authors:fqpnm-r0e70", "collection": "authors", "collection_id": "fqpnm-r0e70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190306-110635099", "type": "article", "title": "A geodesy- and seismicity-based local earthquake likelihood model for central Los Angeles", "author": [ { "family_name": "Rollins", "given_name": "Chris", "orcid": "0000-0002-5291-6956", "clpid": "Rollins-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We estimate time\u2010independent earthquake likelihoods in central Los Angeles using a model of interseismic strain accumulation and the 1932\u20132017 seismic catalog. We assume that on the long\u2010term average, earthquakes and aseismic deformation collectively release seismic moment at a rate balancing interseismic loading, mainshocks obey the Gutenberg\u2010Richter law (a log linear magnitude\u2010frequency distribution [MFD]) up to a maximum magnitude and a Poisson process, and aftershock sequences obey the Gutenberg\u2010Richter and \"B\u00e5th\" laws. We model a comprehensive suite of these long\u2010term systems, assess how likely each system would be to have produced the MFD of the instrumental catalog, and use these likelihoods to probabilistically estimate the long\u2010term MFD. We estimate M_(max) = 6.8 + 1.05/\u22120.4 (every ~300 years) or M_(max) = 7.05 + 0.95/\u22120.4 assuming a truncated or tapered Gutenberg\u2010Richter MFD, respectively. Our results imply that, for example, the (median) likelihood of one or more M_w \u2265 6.5 mainshocks is 0.2% in 1 year, 2% in 10 years, and 18\u201321% in 100 years.", "doi": "10.1029/2018gl080868", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2019-03-28", "series_number": "6", "volume": "46", "issue": "6", "pages": "3153-3162" }, { "id": "authors:583fe-hhw64", "collection": "authors", "collection_id": "583fe-hhw64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190222-084153146", "type": "article", "title": "Triggering of the Mw 7.2 Hawaii earthquake of May 4, 2018 by a dike intrusion", "author": [ { "family_name": "Chen", "given_name": "Kejie", "orcid": "0000-0002-8878-1731", "clpid": "Chen-Kejie" }, { "family_name": "Smith", "given_name": "Jonathan D.", "orcid": "0000-0002-1684-1344", "clpid": "Smith-J-D" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Liu", "given_name": "Zhen", "orcid": "0000-0002-6313-823X", "clpid": "Liu-Zhen" }, { "family_name": "Song", "given_name": "Y. Tony", "orcid": "0000-0001-6903-0804", "clpid": "Song-Y-Tony" }, { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-A" } ], "abstract": "A Mw 7.2 earthquake struck the south flank of Kilauea, Hawaii, on 4 May 2018, following a period of volcanic unrest. To investigate its relationship with the stress changes induced by prior tectonic and magmatic activity, we model the coseismic slip distribution, preintrusion deformation, and dike intrusion using geodetic, seismic, and tsunami observations. The d\u00e9collement beneath the south flank was creeping seaward by ~25 cm/year. Diking started on 20 April and led to fissure eruption on 3 May. The magmatic activity and creep resulted in an onshore U\u2010shaped zone of stress unloading, fringed by an off\u2010shore zone of stress buildup that apparently guided the 2018 rupture. It takes only 20 to 35 years at the preintrusion rate to accumulate a moment deficit equivalent to the moment that was released in 2018. This event falls short of balancing the moment budget since the 1975 Mw 7.7 earthquake.", "doi": "10.1029/2018gl081428", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2019-03-16", "series_number": "5", "volume": "46", "issue": "5", "pages": "2503-2510" }, { "id": "authors:xfafj-kge41", "collection": "authors", "collection_id": "xfafj-kge41", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190321-083801765", "type": "article", "title": "Stabilization of fault slip by fluid injection in the laboratory and in situ", "author": [ { "family_name": "Cappa", "given_name": "Fr\u00e9d\u00e9ric", "orcid": "0000-0003-4859-8024", "clpid": "Cappa-Fr\u00e9d\u00e9ric" }, { "family_name": "Scuderi", "given_name": "Marco Maria", "orcid": "0000-0001-5232-0792", "clpid": "Scuderi-Marco-Maria" }, { "family_name": "Collettini", "given_name": "Cristiano", "orcid": "0000-0002-4828-2516", "clpid": "Collettini-Cristiano" }, { "family_name": "Guglielmi", "given_name": "Yves", "orcid": "0000-0001-9581-7475", "clpid": "Guglielmi-Yves" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Faults can slip seismically or aseismically depending on their hydromechanical properties, which can be measured in the laboratory. Here, we demonstrate that fault slip induced by fluid injection in a natural fault at the decametric scale is quantitatively consistent with fault slip and frictional properties measured in the laboratory. The increase in fluid pressure first induces accelerating aseismic creep and fault opening. As the fluid pressure increases further, friction becomes mainly rate strengthening, favoring aseismic slip. Our study reveals how coupling between fault slip and fluid flow promotes stable fault creep during fluid injection. Seismicity is most probably triggered indirectly by the fluid injection due to loading of nonpressurized fault patches by aseismic creep.", "doi": "10.1126/sciadv.aau4065", "pmcid": "PMC6415952", "issn": "2375-2548", "publisher": "American Association for the Advancement of Science", "publication": "Science Advances", "publication_date": "2019-03", "series_number": "3", "volume": "5", "issue": "3", "pages": "Art. No. eaau4065" }, { "id": "authors:w1fhh-3v002", "collection": "authors", "collection_id": "w1fhh-3v002", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-100648209", "type": "article", "title": "Crustal rheology of southern Tibet constrained from lake-induced viscoelastic deformation", "author": [ { "family_name": "Henriquet", "given_name": "Maxime", "clpid": "Henriquet-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bills", "given_name": "Bruce G.", "clpid": "Bills-B-G" } ], "abstract": "We probe the rheology of the Tibetan lithosphere using the rebound that accompanied climate-driven lake level variations. At the modern decadal time scale, we used deformation around Siling Tso measured from InSAR. At the millennial time scale, we use Holocenepaleoshorelines around Siling Tso and Zhari Nam Tso. We use chronological constraints from the literature and Digital Elevation Models to constrain their ages and geometry. We observe a small post-highstand subsidence of the area near the center of mass of the paleolake-load and a low-amplitude short-wavelength outer bulge. In the context of a model consisting of an elastic lid over a viscous channel with a rigid base, these observations preclude the existence of a thick low viscosity channel and require a thin elastic lid. Based on Monte Carlo inversion, we constrain the range of possible equivalent elastic thickness of the lid (<5 km), the viscosity (2\u00d710^(18)\u201310^(20) Pa.s) and thickness of the crustal channel (<10\u201320 km). By contrast, the modern data requires a stiffer lid with equivalent elastic thickness >20 km and a >20 km thick channel with lower crustal viscosity (<5\u00d710^(18) Pa.s). The different rheologies inferred at these different time-scales could be explained by a Burgers body rheology of the middle and lower crust, with a short-term viscosity of 10^(18) Pa.s and long-term viscosity of 10^(20) Pa.s, or even better by vertical variations of viscosity. To illustrate the latter claim, we show that the observations at the decadal and Holocene time scales can be reconciled by assuming a low viscosity zone (10^(18) Pa.s) at mid-crustal depth (between \u223c10 and 30 km depth) embedded in a higher viscosity crust (>10^(20) Pa.s). In both cases, the interferences in space of the deformation signals induced by the lakes geometry, and in time through the viscoelastic response to the lake level variations results in limited distortion of the paleo-shorelines. While the elastic lid in the upper crust needs in any case to be thin (<10 km), the low amplitude distortion requires significant viscoelastic support from the lower crust and upper mantle; this explains the relatively high effective elastic thickness (>20 km) inferred in some previous studies of Holocene paleoshorelines. In the longer term, the effective elastic thickness of the lithosphere must drop asymptotically to the value of the elastic lid in the upper crust (<10 km); this explains the low effective elastic thickness derived from gravity studies.", "doi": "10.1016/j.epsl.2018.11.014", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2019-01-15", "volume": "506", "pages": "308-322" }, { "id": "authors:nep8j-j9g29", "collection": "authors", "collection_id": "nep8j-j9g29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190107-082842022", "type": "article", "title": "Bimodal seismicity in the Himalaya controlled by fault friction and geometry", "author": [ { "family_name": "Dal Zilio", "given_name": "Luca", "orcid": "0000-0002-5642-0894", "clpid": "Dal-Zilio-Luca" }, { "family_name": "van Dinther", "given_name": "Ylona", "orcid": "0000-0002-4273-8287", "clpid": "van-Dinther-Ylona" }, { "family_name": "Gerya", "given_name": "Taras", "orcid": "0000-0002-1062-2722", "clpid": "Gerya-Taras" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "There is increasing evidence that the Himalayan seismicity can be bimodal: blind earthquakes (up to Mw\u2009~\u20097.8) tend to cluster in the downdip part of the seismogenic zone, whereas infrequent great earthquakes (Mw 8+) propagate up to the Himalayan frontal thrust. To explore the causes of this bimodal seismicity, we developed a two-dimensional, seismic cycle model of the Nepal Himalaya. Our visco-elasto-plastic simulations reproduce important features of the earthquake cycle, including interseismic strain and a bimodal seismicity pattern. Bimodal seismicity emerges as a result of relatively higher friction and a non-planar geometry of the Main Himalayan Thrust fault. This introduces a region of large strength excess that can only be activated once enough stress is transferred upwards by blind earthquakes. This supports the view that most segments of the Himalaya might produce complete ruptures significantly larger than the 2015\u2009Mw 7.8 Gorkha earthquake, which should be accounted for in future seismic hazard assessments.", "doi": "10.1038/s41467-018-07874-8", "pmcid": "PMC6318329", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2019-01-03", "volume": "10", "pages": "Art. No. 48" }, { "id": "authors:tdcjk-de970", "collection": "authors", "collection_id": "tdcjk-de970", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181101-080742326", "type": "article", "title": "A Global Database of Strong\u2010Motion Displacement GNSS Recordings and an Example Application to PGD Scaling", "author": [ { "family_name": "Ruhl", "given_name": "Christine J.", "clpid": "Ruhl-C-J" }, { "family_name": "Melgar", "given_name": "Diego", "clpid": "Melgar-D" }, { "family_name": "Geng", "given_name": "Jianghui", "clpid": "Geng-Jianghui" }, { "family_name": "Goldberg", "given_name": "Dara E.", "clpid": "Goldberg-D-E" }, { "family_name": "Crowell", "given_name": "Brendan W.", "clpid": "Crowell-B-W" }, { "family_name": "Allen", "given_name": "Richard M.", "clpid": "Allen-R-M" }, { "family_name": "Bock", "given_name": "Yehuda", "clpid": "Bock-Y" }, { "family_name": "Barrientos", "given_name": "Sergio", "clpid": "Barrientos-S" }, { "family_name": "Riquelme", "given_name": "Sebastian", "clpid": "Riquelme-S" }, { "family_name": "B\u00e1ez", "given_name": "Juan Carlos", "clpid": "B\u00e1ez-Soto-J-C" }, { "family_name": "Cabral-Cano", "given_name": "Enrique", "orcid": "0000-0002-9143-2401", "clpid": "Cabral-Cano-E" }, { "family_name": "P\u00e9rez-Campos", "given_name": "Xyoli", "orcid": "0000-0001-8970-7966", "clpid": "P\u00e9rez-Campos-Xyoli" }, { "family_name": "Hill", "given_name": "Emma M.", "clpid": "Hill-E-M" }, { "family_name": "Protti", "given_name": "Marino", "clpid": "Protti-M" }, { "family_name": "Ganas", "given_name": "Athanassios", "clpid": "Ganas-A" }, { "family_name": "Ruiz", "given_name": "Mario", "clpid": "Ruiz-M" }, { "family_name": "Mothes", "given_name": "Patricia", "clpid": "Mothes-P" }, { "family_name": "Jarr\u00edn", "given_name": "Paul", "clpid": "Jarr\u00edn-P" }, { "family_name": "Nocquet", "given_name": "Jean\u2010Mathieu", "clpid": "Nocquet-J-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "D'Anastasio", "given_name": "Elisabetta", "clpid": "D'Anastasio-E" } ], "abstract": "Displacement waveforms derived from Global Navigation Satellite System (GNSS) data have become more commonly used by seismologists in the past 15 yrs. Unlike strong\u2010motion accelerometer recordings that are affected by baseline offsets during very strong shaking, GNSS data record displacement with fidelity down to 0 Hz. Unfortunately, fully processed GNSS waveform data are still scarce because of limited public availability and the highly technical nature of GNSS processing. In an effort to further the use and adoption of high\u2010rate (HR) GNSS for earthquake seismology, ground\u2010motion studies, and structural monitoring applications, we describe and make available a database of fully curated HR\u2010GNSS displacement waveforms for significant earthquakes. We include data from HR\u2010GNSS networks at near\u2010source to regional distances (1\u20131000 km) for 29 earthquakes between M_w 6.0 and 9.0 worldwide. As a demonstration of the utility of this dataset, we model the magnitude scaling properties of peak ground displacements (PGDs) for these events. In addition to tripling the number of earthquakes used in previous PGD scaling studies, the number of data points over a range of distances and magnitudes is dramatically increased. The data are made available as a compressed archive with the article.", "doi": "10.1785/0220180177", "issn": "0895-0695", "publisher": "Seismological Society of America", "publication": "Seismological Research Letters", "publication_date": "2019-01", "series_number": "1", "volume": "90", "issue": "1", "pages": "271-279" }, { "id": "authors:pcqwd-1yt53", "collection": "authors", "collection_id": "pcqwd-1yt53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180615-090858454", "type": "article", "title": "Comparing dune migration measured from remote sensing with sand flux prediction based on weather data and model, a test case in Qatar", "author": [ { "family_name": "Michel", "given_name": "Sylvain", "orcid": "0000-0001-7878-6603", "clpid": "Michel-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Ewing", "given_name": "Ryan C.", "orcid": "0000-0001-6337-610X", "clpid": "Ewing-R-C" }, { "family_name": "Vriend", "given_name": "Nathalie", "clpid": "Vriend-N-M" }, { "family_name": "Heggy", "given_name": "Essam", "clpid": "Heggy-E" } ], "abstract": "This study explores validating and calibrating the wind regime predicted by Global Circulation Models (GCM) on Earth and other planets using optical remote sensing of dune dynamics. We use Spot-5 images to track the migration of 64 Barchan dunes in Qatar using the COSI-Corr technique. We estimate the volume of the dunes using a scaling law calibrated from one particular dune, which was surveyed in the field. Using volume and migration rate, we determine the sand flux from a single dune, Q_(Dunes), and scale this estimate to the whole dune field. We compare the measured sand flux with those derived from wind velocity measurements at a local meteorological station as well as with those predicted from ERA-Interim (a Global Circulation Model). The comparison revealed that the wind velocity predicted by ERA-Interim is inappropriate to calculate the sand flux. This is due to the 6-h sampling rate and to systematic bias revealed by a comparison with the local wind data. We describe a simple procedure to correct for these effects. With the proposed correction, similar sand flux are predicted using the local and ERA-Interim data, independently of the value of the value of the shear velocity threshold, u_(*t). The predicted sand flux is about 65% of Q_(Dunes). The agreement is best assuming the value u_(*t)=0.244 m/s, which is only slightly larger than the value of u_(*t)=0.2612 m/s estimated based in the sand granulometry measured from field samples. The influence of the dune topography on the wind velocity field could explain the underestimation. In any case, the study demonstrates the possibility of validating GCM model and calibrating aeolian sand transport laws using remote sensing measurements of dune dynamics and highlights the caveats associated to such an approach.", "doi": "10.1016/j.epsl.2018.05.037", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2018-09-01", "volume": "497", "pages": "12-21" }, { "id": "authors:hq1hr-f5057", "collection": "authors", "collection_id": "hq1hr-f5057", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190306-110634964", "type": "article", "title": "Interseismic Strain Accumulation on Faults Beneath Los Angeles, California", "author": [ { "family_name": "Rollins", "given_name": "Chris", "orcid": "0000-0002-5291-6956", "clpid": "Rollins-Christopher" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Landry", "given_name": "Walter", "clpid": "Landry-Walter" }, { "family_name": "Argus", "given_name": "Donald F.", "orcid": "0000-0002-2770-4257", "clpid": "Argus-D-F" }, { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-Sylvain" } ], "abstract": "Geodetic data show that the Los Angeles metropolitan area is undergoing 8\u20139 mm/year of north\u2010south tectonic shortening associated with the Big Bend of the San Andreas Fault. This shortening has been linked to multiple damaging twentieth century thrust earthquakes as well as possible Mw \u2265 7.0 Holocene thrust events beneath central Los Angeles. To better characterize this seismic hazard, we assess how this shortening is being accommodated by interseismic strain accumulation on subsurface faults, incorporating detailed seismology\u2010 and geology\u2010based models of fault geometry and the low\u2010stiffness Los Angeles sedimentary basin. We find that strain accumulation on local strike\u2010slip faults likely contributes no more than 1\u20132 mm/year of the shortening. We formally invert the geodetic data for the pattern of interseismic strain accumulation on the north dipping Sierra Madre, Puente Hills, and Compton thrust faults and a master decollement. We explore the impact of the assumed material model, strain accumulation on faults to the west and east, and other model assumptions. We infer that the three faults slip at 3\u20134 mm/year over the long term and are currently partially or fully locked and accruing interseismic strain on their upper sections. This locking implies an annual deficit of seismic moment, 1.6 + 1.3/\u22120.5 \u00d7 10^(17) Nm/year in total, which is presumably balanced over the long\u2010term average by the moment released in earthquakes. The depth distribution of moment deficit accumulation rate matches that of seismicity rates in Los Angeles to first order, in part, because the models incorporate the blind nature of the Puente Hills and Compton Faults.", "doi": "10.1029/2017jb015387", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2018-08", "series_number": "8", "volume": "123", "issue": "8", "pages": "7126-7150" }, { "id": "authors:4zr9n-x9475", "collection": "authors", "collection_id": "4zr9n-x9475", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171017-110101413", "type": "article", "title": "Lag and mixing during sediment transfer across the Tian Shan piedmont caused by climate-driven aggradation-incision cycles", "author": [ { "family_name": "Malatesta", "given_name": "Luca C.", "clpid": "Malatesta-L-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Brown", "given_name": "Nathan D.", "clpid": "Brown-N-D" }, { "family_name": "Breitenbach", "given_name": "Sebastian F. M.", "clpid": "Breitenbach-S-F-M" }, { "family_name": "Pan", "given_name": "Jiawei", "clpid": "Pan-Jiawei" }, { "family_name": "Chevalier", "given_name": "Marie-Luce", "clpid": "Chevalier-M-L" }, { "family_name": "Rhodes", "given_name": "Edward", "clpid": "Rhodes-E-J" }, { "family_name": "Saint-Carlier", "given_name": "Dimitri", "clpid": "Saint-Carlier-D" }, { "family_name": "Zhang", "given_name": "Wenjing", "clpid": "Zhang-Wenjing" }, { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Lav\u00e9", "given_name": "J\u00e9r\u00f4me", "clpid": "Lav\u00e9-J" }, { "family_name": "Blard", "given_name": "Pierre-Henri", "clpid": "Blard-P-H" } ], "abstract": "Transient sediment storage and mixing of deposits of various ages during transport across alluvial piedmonts alters the clastic sedimentary record. We quantify buffering and mixing during cycles of aggradation-incision in the north piedmont of the Eastern Tian Shan. We complement existing chronologic data with 20 new luminescence ages and one cosmogenic radionuclide age of terrace abandonment and alluvial aggradation. Over the last 0.5 Myrs, the piedmont deeply incised and aggraded many times per 100 kyr. Aggradation is driven by an increased flux of glacial sediment accumulated in the high range and flushed onto the piedmont by greater water discharge at stadial-interstadial transitions. After this sediment is evacuated from the high range, the reduced input sediment flux results in fluvial incision of the piedmont as fast as 9 cm/yr and to depths up to 330 m. The timing of incision onset is different in each river and does not directly reflect climate forcing but the necessary time for the evacuation of glacial sediment from the high range. A significant fraction of sediments evacuated from the high range is temporarily stored on the piedmont before a later incision phase delivers it to the basin. Coarse sediments arrive in the basin with a lag of at least 7 to 14 kyrs between the first evacuation from the mountain and later basinward transport. The modern output flux of coarse sediments from the piedmont contains a significant amount of recycled material that was deposited on the piedmont as early as the Middle Pleistocene. Variations in temperature and moisture delivered by the Westerlies are the likely cause of repeated aggradation-incision cycles in the north piedmont instead of monsoonal precipitation. The arrival of the gravel front into the proximal basin is delayed relative to the fine-grained load and both are separated by a hiatus. This work shows, based on field observations and data, how sedimentary systems respond to climatic perturbations, and how sediment recycling and mixing can ensue.", "doi": "10.1111/bre.12267", "issn": "0950-091X", "publisher": "Wiley", "publication": "Basin Research", "publication_date": "2018-08", "series_number": "4", "volume": "30", "issue": "4", "pages": "613-635" }, { "id": "authors:mv8pe-wy195", "collection": "authors", "collection_id": "mv8pe-wy195", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180612-083811607", "type": "article", "title": "Contrasting river incision in north and south Tian Shan piedmonts due to variable glacial imprint in mountain valleys", "author": [ { "family_name": "Malatesta", "given_name": "Luca C.", "clpid": "Malatesta-L-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Fluvial terraces carved by incising rivers are widely used to investigate external forcing by climate and tectonics. In the Eastern Tian Shan (Central Asia), the north piedmont rivers are much more deeply incised (mean: 124 m) compared to the south piedmont (mean: 17 m) despite very similar tectonic and climatic settings. We attribute the incision contrast to a difference in glacial imprint between southern and northern catchments. Whereas the upper halves of the valleys in the northern higher subrange are formerly glaciated, wide and gently sloping, U-shaped valleys flowing into V-shaped valleys, the valleys of the lower southern subrange are entirely V-shaped. The glacially widened valleys act as capacitors that accumulate and release glacial and periglacial sediment onto the piedmont. The resulting discrete pulse in sediment flux, Q_s, forces aggradation and steepening, followed by incision and gentler slopes of the piedmont rivers. The fluvial valleys do not accumulate sediment, and changes in water discharge primarily control the slope of the piedmont rivers. Today, incision in the north is associated with the drop in Q_s that occurred after depletion of the upstream reservoir, while aggradation in the south is due to Central Asian aridity. The same climatic forcing can have strikingly distinct morphological expressions downstream of catchments with different glacial imprints.", "doi": "10.1130/G40320.1", "issn": "0091-7613", "publisher": "Geological Society of America", "publication": "Geology", "publication_date": "2018-07-01", "series_number": "7", "volume": "46", "issue": "7", "pages": "659-662" }, { "id": "authors:hhjp4-cvz95", "collection": "authors", "collection_id": "hhjp4-cvz95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180228-085254520", "type": "article", "title": "Late Pleistocene acceleration of deformation across the northern Tianshan piedmont (China) evidenced from the morpho-tectonic evolution of the Dushanzi anticline", "author": [ { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Saint-Carlier", "given_name": "Dimitri", "clpid": "Saint-Carlier-D" }, { "family_name": "Lav\u00e9", "given_name": "J\u00e9r\u00f4me", "clpid": "Lav\u00e9-J" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Blard", "given_name": "Pierre-Henri", "clpid": "Blard-P-H" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Brown", "given_name": "Nathan D.", "clpid": "Brown-N-D" }, { "family_name": "Malatesta", "given_name": "Luca Claude", "clpid": "Malatesta-L-C" }, { "family_name": "Shengli", "given_name": "Wang", "clpid": "Shengli-Wang" }, { "family_name": "Rhodes", "given_name": "Edward J.", "clpid": "Rhodes-E-J" } ], "abstract": "We document the temporal evolution of deformation in the northern Tianshan piedmont where the deformation is partitioned across several thrusts and folds. We focus on the Dushanzi anticline, where abandoned terraces and growth strata allow us to constrain the history of folding since the Miocene. Based on subsurface seismic imaging, structural measurements and morphological analysis, we show that this anticline is associated with two decollement levels. We use kink band migration in growth strata dated by paleomagnetism to constrain the shortening from the Mio-Pliocene to the Holocene. Our results show that the Dushanzi anticline has been active since at least 8\u202fMa and that the fold grew at a steady shortening rate of 0.6\u202f\u00b1\u202f0.1\u202fmm/yr from 8 to ~1.5\u202fMa with possible variations from 2.5 to 1.5\u202fMa. Then it accelerated rapidly to a rate of 4.3\u202f\u00b1\u202f1.0\u202fmm/yr over at least the last 100\u202fka. These results, together with similar temporal shortening evolutions across other structures, suggest that the deformation rate across the eastern Tianshan piedmont increased relatively recently. This may reflect either a redistribution of the deformation from the internal structures toward the borders or a general acceleration of the deformation across the entire range.", "doi": "10.1016/j.tecto.2018.02.016", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2018-04-04", "volume": "730", "pages": "132-140" }, { "id": "authors:0d6z0-jtk95", "collection": "authors", "collection_id": "0d6z0-jtk95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180620-104204252", "type": "article", "title": "Toward a Global Horizontal and Vertical Elastic Load Deformation Model Derived from GRACE and GNSS Station Position Time Series", "author": [ { "family_name": "Chanard", "given_name": "Kristel", "orcid": "0000-0001-9934-9621", "clpid": "Chanard-K" }, { "family_name": "Fleitout", "given_name": "Luce", "orcid": "0000-0003-1114-3616", "clpid": "Fleitout-L" }, { "family_name": "Calais", "given_name": "Eric", "orcid": "0000-0002-5935-8117", "clpid": "Calais-E" }, { "family_name": "Rebischung", "given_name": "Paul", "clpid": "Rebischung-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We model surface displacements induced by variations in continental water, atmospheric pressure, and nontidal oceanic loading, derived from the Gravity Recovery and Climate Experiment (GRACE) for spherical harmonic degrees two and higher. As they are not observable by GRACE, we use at first the degree\u20101 spherical harmonic coefficients from Swenson et al. (2008, https://doi.org/10.1029/2007JB005338). We compare the predicted displacements with the position time series of 689 globally distributed continuous Global Navigation Satellite System (GNSS) stations. While GNSS vertical displacements are well explained by the model at a global scale, horizontal displacements are systematically underpredicted and out of phase with GNSS station position time series. We then reestimate the degree 1 deformation field from a comparison between our GRACE\u2010derived model, with no a priori degree 1 loads, and the GNSS observations. We show that this approach reconciles GRACE\u2010derived loading displacements and GNSS station position time series at a global scale, particularly in the horizontal components. Assuming that they reflect surface loading deformation only, our degree\u20101 estimates can be translated into geocenter motion time series. We also address and assess the impact of systematic errors in GNSS station position time series at the Global Positioning System (GPS) draconitic period and its harmonics on the comparison between GNSS and GRACE\u2010derived annual displacements. Our results confirm that surface mass redistributions observed by GRACE, combined with an elastic spherical and layered Earth model, can be used to provide first\u2010order corrections for loading deformation observed in both horizontal and vertical components of GNSS station position time series.", "doi": "10.1002/2017JB015245", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2018-04", "series_number": "4", "volume": "123", "issue": "4", "pages": "3225-3237" }, { "id": "authors:pp0kz-q4y46", "collection": "authors", "collection_id": "pp0kz-q4y46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180411-105832773", "type": "article", "title": "Constraints on Transient Viscoelastic Rheology of the Asthenosphere From Seasonal Deformation", "author": [ { "family_name": "Chanard", "given_name": "Kristel", "orcid": "0000-0001-9934-9621", "clpid": "Chanard-K" }, { "family_name": "Fleitout", "given_name": "Luce", "orcid": "0000-0003-1114-3616", "clpid": "Fleitout-L" }, { "family_name": "Calais", "given_name": "Eric", "orcid": "0000-0002-5935-8117", "clpid": "Calais-E" }, { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We discuss the constraints on short\u2010term asthenospheric viscosity provided by seasonal deformation of the Earth. We use data from 195 globally distributed continuous Global Navigation Satellite System stations. Surface loading is derived from the Gravity Recovery and Climate Experiment and used as an input to predict geodetic displacements. We compute Green's functions for surface displacements for a purely elastic spherical reference Earth model and for viscoelastic Earth models. We show that a range of transient viscoelastic rheologies derived to explain the early phase of postseismic deformation may induce a detectable effect on the phase and amplitude of horizontal displacements induced by seasonal loading at long wavelengths (1,300\u20134,000 km). By comparing predicted and observed seasonal horizontal motion, we conclude that transient asthenospheric viscosity cannot be lower than 5 \u00d7 10^(17) Pa.s, suggesting that low values of transient asthenospheric viscosities reported in some postseismic studies cannot hold for the seasonal deformation global average.", "doi": "10.1002/2017GL076451", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2018-03-16", "series_number": "5", "volume": "45", "issue": "5", "pages": "2328-2338" }, { "id": "authors:e63wh-ygb80", "collection": "authors", "collection_id": "e63wh-ygb80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171128-100137887", "type": "article", "title": "Seismic and Aseismic Moment Budget and Implication for the Seismic Potential of the Parkfield Segment of the San Andreas Fault", "author": [ { "family_name": "Michel", "given_name": "Sylvain", "orcid": "0000-0001-7878-6603", "clpid": "Michel-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Jolivet", "given_name": "Romain", "orcid": "0000-0002-9896-3651", "clpid": "Jolivet-R" }, { "family_name": "Wang", "given_name": "Lifeng", "clpid": "Wang-Lifeng" } ], "abstract": "This study explores methods to assess the seismic potential of a fault based on geodetic measurements, geological information of fault\u2010slip rate, and seismicity data. The methods are applied to the Parkfield section along the San Andreas fault (SAF) at the transition zone between the SAF creeping segment in the north and the locked section of Cholame to the south, where M_w \u223c6 earthquakes occurred every 24.5 yrs on average since the 1857 M_w 7.7 Fort Tejon earthquake. We compare the moment released by the known earthquakes and associated postseismic deformation with the moment deficit accumulated during the interseismic period derived from geodetic measurement of interseismic strain. We find that the recurring M_w 6 earthquakes are insufficient to balance the slip budget. We discuss and evaluate various possible scenarios which might account for the residual moment deficit and implications of the possible magnitude and return period of M_w >6 earthquakes on that fault segment. The most likely explanation is that this fault segment hosts M_w 6.5\u20137.5 earthquakes, with a return period of 140\u2013300 yrs. Such events could happen as independent earthquakes in conjunction with ruptures of the Carrizo plain segment of the SAF. We show how the results from our analysis can be formally incorporated in probabilistic seismic hazard assessment assuming various magnitude\u2013frequency distribution and renewal time models.", "doi": "10.1785/0120160290", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2018-02", "series_number": "1", "volume": "108", "issue": "1", "pages": "19-38" }, { "id": "authors:wm30c-xzt07", "collection": "authors", "collection_id": "wm30c-xzt07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171003-111456097", "type": "article", "title": "Denudation outpaced by crustal thickening in the eastern Tianshan", "author": [ { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Saint-Carlier", "given_name": "Dimitri", "clpid": "Saint-Carlier-D" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Lave", "given_name": "J\u00e9r\u00f4me", "clpid": "Lav\u00e9-J" }, { "family_name": "Blard", "given_name": "Pierre-Henri", "clpid": "Blard-P-H" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Jolivet", "given_name": "Marc", "clpid": "Jolivet-M" }, { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Wang", "given_name": "ShengLi", "clpid": "Wang-ShengLi" }, { "family_name": "Brown", "given_name": "Nathan David", "clpid": "Brown-N-D" }, { "family_name": "Malatesta", "given_name": "Luca Claude", "clpid": "Malatesta-L-C" }, { "family_name": "Rhodes", "given_name": "Edward", "clpid": "Rhodes-E-J" }, { "literal": "ASTER Team" } ], "abstract": "The modern high topography of the Tianshan resulted from the reactivation of a Paleozoic orogenic belt by the India/Asia collision. Today, the range exhibits tectonically active forelands and intermontane basins. Based on quantitative morphotectonic observations and age constraints derived from cosmogenic 10Be dating, single-grain post-infrared infrared stimulated luminescence (p-IR IRSL) dating and modeling of fault scarp degradation, we quantify the deformation in the Nalati and Bayanbulak intermontane basins in the central Eastern Tianshan. Our results indicate that at least 1.4 mm/yr of horizontal crustal shortening is accommodated within these two basins. This shortening represents over 15% of the 8.5 \u00b1 0.5 mm/yr total shortening rate across the entire range at this longitude. This shortening rate implies that the Eastern Central Tianshan is thickening at a mean rate of \u223c1.4 mm/yr, a rate that is significantly higher than the average denudation rate of 0.14 mm/yr derived from our cosmogenic analysis. This discrepancy suggests that the Tianshan range has not yet reached a steady-state topography and remains in a transient state of topographic growth, most likely due to limited denudation rates driven by the arid climate of Central Asia.", "doi": "10.1016/j.epsl.2017.09.025", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2017-12-01", "volume": "479", "pages": "179-191" }, { "id": "authors:0tjbc-5jy13", "collection": "authors", "collection_id": "0tjbc-5jy13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171220-134657325", "type": "article", "title": "Determination of M_(max) from Background Seismicity and Moment Conservation", "author": [ { "family_name": "Stevens", "given_name": "V. L.", "clpid": "Stevens-V-L" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We describe a simple method to determine the probability distribution function of the magnitude M_(max) and return period T_R of the maximum plausible earthquake on crustal faults. The method requires the background seismicity rate (estimated from instrumental data) and the rate of interseismic moment buildup. The method assumes that the moment released by the seismic slip is in balance with the moment deficit accumulated in between earthquakes. It also assumes that the seismicity obeys the Gutenberg\u2013Richter (GR) law up to M_(max) . We took into account the aftershocks of large infrequent events that were not represented in the instrumental record, so that we could estimate the average seismicity rate over the entire fault history. We extrapolated the instrumental record, using the GR law to model the frequency of larger events and their aftershocks. This increased the frequencies of smaller events on average; when these smaller events were newly extrapolated, they predicted a higher frequency of larger events. We iterated this process until stability was reached, and then we assumed moment balance when we found the maximum magnitude; we have found this method to be appropriate in applications involving examples of fault with good historical catalogs. We then showed examples of applications to faults with no historical catalogs. We present results from nine cases. For the San Andreas fault system, we find M_(max)=8.1\u00b10.3, with T_R380^(950)_(120)yrs ; for the North Anatolian fault, M_(max)=8.0\u00b10.3, with T_R275^(650)_(135)yrs ; for the Main Himalayan thrust, M_(max)=9.0\u00b10.2, with T_R1200^(2700)_(550)yrs; for the Japan trench, M_(max)=9.3\u00b10.3, with T_R520^(1200)_(220)yrs; for the Sumatra\u2013Andaman trench, M_(max)=9.0\u00b10.3, with T_R200^(450)_(80)yrs ; for the Bocon\u00f3 fault, M_(max)=7.3\u00b10.3, with T_R160^(360)_(70)yrs; for the Altyn Tagh fault, M_(max)=8.0\u00b10.3, with T_R900^(2000)_(400)yrs; for the Dead Sea Transform, M_(max)=7.8\u00b10.3, with T_R1000^(2400)_(450)yrs; and for the Kunlun fault, M_(max)=8.0\u00b10.3, with T_R1000^(2000)_(450)yrs.", "doi": "10.1785/0120170022", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2017-12", "series_number": "6", "volume": "107", "issue": "6", "pages": "2578-2596" }, { "id": "authors:k56jh-jmm38", "collection": "authors", "collection_id": "k56jh-jmm38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170911-080518933", "type": "article", "title": "Early Neogene foreland of the Zagros, implications for the initial closure of the Neo-Tethys and kinematics of crustal shortening", "author": [ { "family_name": "Pirouz", "given_name": "Mortaza", "orcid": "0000-0002-7569-492X", "clpid": "Pirouz-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hassanzadeh", "given_name": "Jamshid", "clpid": "Hassanzadeh-J" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Bahroudi", "given_name": "Abbas", "clpid": "Bahroudi-A" } ], "abstract": "We study the transition from passive margin to foreland basin sedimentation now exposed in the High Zagros belt to provide chronological constraints on the initial stage of Arabia\u2013Eurasia collision and closure of the Neo-Tethys. We performed magnetostratigraphy and strontium isotope stratigraphy along two sections near the Zagros suture which expose the oldest preserved foreland deposits: the Shalamzar section in the west and the Dehmoord section in the east. The top of the passive margin Asmari formation has an age of 28\u201329 Ma in the High Zagros and is overlain by foreland deposits with a major basal unconformity representing 7 Myr of hiatus. The base of the foreland deposits has an age of 21.5 Ma at Dehmoord and ca. 26 Ma at Shalamzar. The sedimentation rate increased from 30 m/Myr in the passive margin to 247 m/Myr in the foreland. Combined with available age constraints across the Zagros, our results show that the unconformity is diachronous and records the southwestward migration of the flexural bulge within the Arabian plate at an average rate of 24 \u00b1 2 mm/yr over the last 27 Ma. The time evolution of sediment accumulation in the Zagros foreland follows the prediction from a flexural model, as the foreland is thrust beneath the orogenic wedge and loaded by the wedge and basin fill. We detect the onset of forebulge formation within the Asmari Formation around 25 Ma. We conclude that closure of the Neo-Tethys formed the Zagros collisional wedge at 27 \u00b1 2 Ma. Hence, the Arabia\u2013Eurasia collision was probably not the main driver of global cooling which started near the Eocene\u2013Oligocene boundary (ca. 33.7 Ma). We estimate 650 km of forebulge migration since the onset of the collision which consists of 350 km of shortening across the orogen, and 300 km of widening of the wedge and increasing flexural rigidity of Arabia. We conclude the average rate of shortening across the Zagros to be ca. 13 mm/yr over the last 27 Myr; a value comparable to the modern rate. Palinspastic restoration of structural cross-sections and crustal volume conservation comprise only ca. 200 km of shortening across the Zagros and metamorphic Sanandaj\u2013Sirjan belt implying that at least 150 km of the Arabian crust was underthrust beneath Eurasia without contributing to crustal thickening, possibly due to eclogitization.", "doi": "10.1016/j.epsl.2017.07.046", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2017-11-01", "volume": "477", "pages": "168-182" }, { "id": "authors:y98na-kse28", "collection": "authors", "collection_id": "y98na-kse28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171109-110007329", "type": "article", "title": "Pre- and post-seismic deformation related to the 2015, M_w 7.8 Gorkha earthquake, Nepal", "author": [ { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" }, { "family_name": "Genrich", "given_name": "Joachim F.", "clpid": "Genrich-J-F" }, { "family_name": "Blewitt", "given_name": "Geoffrey", "clpid": "Blewitt-G" }, { "family_name": "Adhikari", "given_name": "Lok Bijaya", "clpid": "Adhikari-L-B" }, { "family_name": "Koirala", "given_name": "Bharat Prasad", "clpid": "Koirala-B-P" }, { "family_name": "Gupta", "given_name": "Ratnamani", "clpid": "Gupta-R" }, { "family_name": "Upreti", "given_name": "Bishal Nath", "clpid": "Upreti-B-N" }, { "family_name": "Pratt-Sitaula", "given_name": "Beth", "clpid": "Pratt-Sitaula-B" }, { "family_name": "Liu-Zeng", "given_name": "Jing", "clpid": "Liu-Zeng-Jing" } ], "abstract": "We analyze time series from continuously recording GPS stations in Nepal spanning the pre- and post-seismic period associated to the M_w7.8 Gorkha earthquake which ruptured the Main Himalayan Thrust (MHT) fault on April 25th, 2015. The records show strong seasonal variations due to surface hydrology. After corrections for these variations, the time series covering the pre- and post-seismic periods do not show any detectable transient pre-seismic displacement. By contrast, a transient post-seismic signal is clear. The observed signal shows southward displacements consistent with afterslip on the MHT. Using additional data from stations deployed after the mainshock, we invert the time series for the spatio-temporal evolution of slip on the MHT. This modelling indicates afterslip dominantly downdip of the mainshock rupture. Two other regions show significant afterslip: a more minor zone updip of the rupture, and a region between the mainshock and the largest aftershock ruptures. Afterslip in the first ~ 7 months after the mainshock released a moment of [12.8 \u00b1 0.5] \u00d7 10^(19) Nm which represents 17.8 \u00b1 0.8% of the co-seismic moment. The moment released by aftershocks over that period of time is estimated to 2.98 \u00d7 10^(19) Nm. Geodetically observed post-seismic deformation after co-seismic offset correction was thus 76.7 \u00b1 1.0% aseismic. The logarithmic time evolution of afterslip is consistent with rate-strengthening frictional sliding. According to this theory, and assuming a long-term loading velocity modulated on the basis of the coupling map of the region and the long term slip rate of 20.2 \u00b1 1.1 mm/yr, afterslip should release about 34.0 \u00b1 1.4% of the co-seismic moment after full relaxation of post-seismic deformation. Afterslip contributed to loading the shallower portion of the MHT which did not rupture in 2015 and stayed locked afterwards. The risk for further large earthquakes in Nepal remains high both updip of the rupture area of the Gorkha earthquake and West of Kathmandu where the MHT has remained locked and where no earthquake larger than M_w7.5 has occurred since 1505.", "doi": "10.1016/j.tecto.2016.06.014", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2017-09-13", "volume": "714-715", "pages": "90-106" }, { "id": "authors:m4h85-f4q35", "collection": "authors", "collection_id": "m4h85-f4q35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161104-103904641", "type": "article", "title": "Ductile shearing to brittle thrusting along the Nepal Himalaya: Linking Miocene channel flow and critical wedge tectonics to 25th April 2015 Gorkha earthquake", "author": [ { "family_name": "Searle", "given_name": "Mike", "clpid": "Searle-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Elliott", "given_name": "John", "clpid": "Elliott-J-G" }, { "family_name": "Dyck", "given_name": "Brendan", "clpid": "Dyck-B" } ], "abstract": "The 25th April 2015 magnitude 7.8 Gorkha earthquake in Nepal ruptured the Main Himalayan thrust (MHT) for ~ 140 km east-west and ~ 50 km across strike. The earthquake nucleated at a depth of ~ 15\u201318 km approximating to the brittle-ductile transition and propagated east along the MHT but did not rupture to the surface, leaving half of the fault extent still locked beneath the Siwalik hills. Coseismic slip shows that motion is confined to the ramp-flat geometry of the MHT and there was no out-of-sequence movement along the Main Central Thrust (MCT). Below 20 km depth, the MHT is a creeping, aseismic ductile shear zone. Cumulated deformation over geological time has exhumed the deeper part of the Himalayan orogen which is now exposed in the Greater Himalaya revealing a tectonic history quite different from presently active tectonics. There, early Miocene structures, including the MCT, are almost entirely ductile, with deformation occurring at temperatures higher than ~ 400 \u00b0C, and were active between ~ 22\u201316 Ma. Kyanite and sillimanite-grade gneisses and migmatites approximately 5\u201320 km thick in the core of the Greater Himalayan Sequence (GHS) together with leucogranite intrusions along the top of the GHS were extruded southward between ~ 22\u201315 Ma, concomitant with ages of partial melting. Thermobarometric constraints show that ductile extrusion of the GHS during the Miocene occurred at muscovite-dehydration temperatures ~ 650-775 \u00b0C, and thus brittle thrusting and critical taper models for GHS deformation are unrealistic. As partial melting and channel flow ceased at ~ 15 Ma, brittle thrusting and underplating associated with duplex formation occurred along the Lesser Himalaya passively uplifting the GHS.", "doi": "10.1016/j.tecto.2016.08.003", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2017-09-13", "volume": "714-715", "pages": "117-124" }, { "id": "authors:1bgnp-74m19", "collection": "authors", "collection_id": "1bgnp-74m19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171005-083018196", "type": "article", "title": "Flexural bending of the Zagros foreland basin", "author": [ { "family_name": "Pirouz", "given_name": "Mortaza", "orcid": "0000-0002-7569-492X", "clpid": "Pirouz-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Gualandi", "given_name": "Adriano", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-A" }, { "family_name": "Hassanzadeh", "given_name": "Jamshid", "clpid": "Hassanzadeh-J" }, { "family_name": "Sternai", "given_name": "Pietro", "clpid": "Sternai-P" } ], "abstract": "We constrain and model the geometry of the Zagros foreland to assess the equivalent elastic thickness of the northern edge of the Arabian plate and the loads that have originated due to the Arabia\u2013Eurasia collision. The Oligo-Miocene Asmari formation, and its equivalents in Iraq and Syria, is used to estimate the post-collisional subsidence as they separate passive margin sediments from the younger foreland deposits. The depth to these formations is obtained by synthesizing a large database of well logs, seismic profiles and structural sections from the Mesopotamian basin and the Persian Gulf. The foreland depth varies along strike of the Zagros wedge between 1 and 6\u2009km. The foreland is deepest beneath the Dezful embayment, in southwest Iran, and becomes shallower towards both ends. We investigate how the geometry of the foreland relates to the range topography loading based on simple flexural models. Deflection of the Arabian plate is modelled using point load distribution and convolution technique. The results show that the foreland depth is well predicted with a flexural model which assumes loading by the basin sedimentary fill, and thickened crust of the Zagros. The model also predicts a Moho depth consistent with Free-Air anomalies over the foreland and Zagros wedge. The equivalent elastic thickness of the flexed Arabian lithosphere is estimated to be ca. 50\u2009km. We conclude that other sources of loading of the lithosphere, either related to the density variations (e.g. due to a possible lithospheric root) or dynamic origin (e.g. due to sublithospheric mantle flow or lithospheric buckling) have a negligible influence on the foreland geometry, Moho depth and topography of the Zagros. We calculate the shortening across the Zagros assuming conservation of crustal mass during deformation, trapping of all the sediments eroded from the range in the foreland, and an initial crustal thickness of 38\u2009km. This calculation implies a minimum of 126 \u00b1 18\u2009km of crustal shortening due to ophiolite obduction and post-collisional shortening.", "doi": "10.1093/gji/ggx252", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2017-09", "series_number": "3", "volume": "210", "issue": "3", "pages": "1659-1680" }, { "id": "authors:88mvq-jx760", "collection": "authors", "collection_id": "88mvq-jx760", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170808-080406085", "type": "article", "title": "Aftershocks driven by afterslip and fluid pressure sweeping through a fault-fracture mesh", "author": [ { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Rollins", "given_name": "Christopher", "orcid": "0000-0002-5291-6956", "clpid": "Rollins-C" }, { "family_name": "Cochran", "given_name": "Elizabeth S.", "orcid": "0000-0003-2485-4484", "clpid": "Cochran-E-S" }, { "family_name": "Hauksson", "given_name": "Egill", "orcid": "0000-0002-6834-5051", "clpid": "Hauksson-E" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ben-Zion", "given_name": "Yehuda", "orcid": "0000-0002-9602-2014", "clpid": "Ben-Zion-Y" } ], "abstract": "A variety of physical mechanisms are thought to be responsible for the triggering and spatiotemporal evolution of aftershocks. Here we analyze a vigorous aftershock sequence and postseismic geodetic strain that occurred in the Yuha Desert following the 2010 M_w 7.2 El Mayor-Cucapah earthquake. About 155,000 detected aftershocks occurred in a network of orthogonal faults and exhibit features of two distinct mechanisms for aftershock triggering. The earliest aftershocks were likely driven by afterslip that spread away from the main shock with the logarithm of time. A later pulse of aftershocks swept again across the Yuha Desert with square root time dependence and swarm-like behavior; together with local geological evidence for hydrothermalism, these features suggest that the events were driven by fluid diffusion. The observations illustrate how multiple driving mechanisms and the underlying fault structure jointly control the evolution of an aftershock sequence.", "doi": "10.1002/2017GL074634", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2017-08-28", "series_number": "16", "volume": "44", "issue": "16", "pages": "8260-8267" }, { "id": "authors:70t37-k4742", "collection": "authors", "collection_id": "70t37-k4742", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170817-075028405", "type": "article", "title": "Pulse-Like Partial Ruptures and High-Frequency Radiation at Creeping-Locked Transition during Megathrust Earthquakes", "author": [ { "family_name": "Michel", "given_name": "Sylvain", "orcid": "0000-0001-7878-6603", "clpid": "Michel-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Jiang", "given_name": "Junle", "orcid": "0000-0002-8796-5846", "clpid": "Jiang-Junle" } ], "abstract": "Megathrust earthquakes tend to be confined to fault areas locked in the interseismic period and often rupture them only partially. For example, during the 2015 M7.8 Gorkha earthquake, Nepal, a slip pulse propagating along strike unzipped the bottom edge of the locked portion of the Main Himalayan Thrust (MHT). The lower edge of the rupture produced dominant high-frequency (>1 Hz) radiation of seismic waves. We show that similar partial ruptures occur spontaneously in a simple dynamic model of earthquake sequences. The fault is governed by standard laboratory-based rate-and-state friction with the aging law and contains one homogenous velocity-weakening (VW) region embedded in a velocity-strengthening (VS) area. Our simulations incorporate inertial wave-mediated effects during seismic ruptures (they are thus fully dynamic) and account for all phases of the seismic cycle in a self-consistent way. Earthquakes nucleate at the edge of the VW area and partial ruptures tend to stay confined within this zone of higher prestress, producing pulse-like ruptures that propagate along strike. The amplitude of the high-frequency sources is enhanced in the zone of higher, heterogeneous stress at the edge of the VW area.", "doi": "10.1002/2017GL074725", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2017-08-28", "series_number": "16", "volume": "44", "issue": "16", "pages": "8345-8351" }, { "id": "authors:ddabv-kdq45", "collection": "authors", "collection_id": "ddabv-kdq45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170831-144217593", "type": "article", "title": "Aseismic deformation associated with an earthquake swarm in the northern Apennines (Italy)", "author": [ { "family_name": "Gualandi", "given_name": "A.", "orcid": "0000-0002-3100-8932", "clpid": "Gualandi-A" }, { "family_name": "Nichele", "given_name": "C.", "clpid": "Nichele-C" }, { "family_name": "Serpelloni", "given_name": "E.", "orcid": "0000-0003-1822-403X", "clpid": "Serpelloni-E" }, { "family_name": "Chiaraluce", "given_name": "L.", "orcid": "0000-0002-9697-6504", "clpid": "Chiaraluce-L" }, { "family_name": "Anderlini", "given_name": "L.", "orcid": "0000-0002-9461-3320", "clpid": "Anderlini-L" }, { "family_name": "Latorre", "given_name": "D.", "orcid": "0000-0002-4594-0317", "clpid": "Latorre-D" }, { "family_name": "Belardinelli", "given_name": "M. E.", "orcid": "0000-0002-7653-5090", "clpid": "Belardinelli-M-E" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Analyzing the displacement time series from continuous GPS (cGPS) with an Independent Component Analysis, we detect a transient deformation signal that correlates both in space and time with a seismic swarm activity (maximum M_w=3.69 \u00b1 0.09) occurred in the hanging wall of the Altotiberina normal fault (Northern Apennines, Italy) in 2013\u20132014. The geodetic transient lasted \u223c6 months and produced a NW-SE trending extension of \u223c5.3 mm, consistent with the regional tectonic regime. The seismicity and the geodetic signal are consistent with slip on two splay faults in the Altotiberina fault (ATF) hanging wall. Comparing the seismic moment associated with the geodetic transient and the seismic events, we observe that seismicity accounts for only a fraction of the measured geodetic deformation. The combined seismic and aseismic slip decreased the Coulomb stress on the locked shallow portion of the ATF, while the transition region to the creeping section has been loaded.", "doi": "10.1002/2017GL073687", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2017-08-16", "series_number": "15", "volume": "44", "issue": "15", "pages": "7706-7714" }, { "id": "authors:bqkcs-aj546", "collection": "authors", "collection_id": "bqkcs-aj546", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170831-074652571", "type": "article", "title": "Testing monsoonal controls on bedrock river incision in the Himalaya and Eastern Tibet with a stochastic-threshold stream power model", "author": [ { "family_name": "Scherler", "given_name": "Dirk", "orcid": "0000-0003-3911-2803", "clpid": "Scherler-D" }, { "family_name": "DiBiase", "given_name": "Roman A.", "orcid": "0000-0002-5347-8396", "clpid": "DiBiase-R-A" }, { "family_name": "Fisher", "given_name": "G. Burch", "clpid": "Fisher-G-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "^(10)Be-derived catchment average erosion rates from the Himalaya and Eastern Tibet show different relationships with normalized channel steepness index (k_(sn)), suggesting differences in erosional efficiency of bedrock river incision. We used a threshold stream power model (SPM) combined with a stochastic distribution of discharges to explore the extent to which this observation can be explained by differences in the mean and variability of discharge between the two regions. Based on the analysis of 199 daily discharge records (record lengths 3\u201345 years; average 18.5 years), we parameterized monsoonal discharge with a weighted sum of two inverse gamma distributions. During both high- and low-flow conditions, annual and interannual discharge variabilities are similarly low in each region. Channel widths for 36 rivers indicate, on average, 25% wider streams in Eastern Tibet than in the Himalaya. Because most catchments with ^(10)Be data are not gauged, we constrained mean annual discharge in these catchments using gridded precipitation data sets that we calibrated to the available discharge records. Comparing ^(10)Be-derived with modeled erosion rates, the stochastic-threshold SPM explains regional differences better than a simple SPM based on drainage area or mean annual runoff. Systematic differences at small k_(sn) values can be reconciled with k_(sn)-dependent erosion thresholds, whereas substantial scatter for high k_(sn) values persists, likely due to methodological limitations. Sensitivity analysis of the stochastic-threshold SPM calibrated to the Himalaya indicates that changes in the duration or strength of summer monsoon precipitation have the largest effect on erosional efficiency, while changes in monsoonal discharge variability have almost no effect. The modeling approach presented in this study can in principle be used to assess the impact of precipitation changes on erosion.", "doi": "10.1002/2016JF004011", "issn": "2169-9003", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Earth Surface", "publication_date": "2017-07", "series_number": "7", "volume": "122", "issue": "7", "pages": "1389-1429" }, { "id": "authors:sd7ay-39b26", "collection": "authors", "collection_id": "sd7ay-39b26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170320-124537893", "type": "article", "title": "Dynamically triggered slip on a splay fault in the M_w 7.8, 2016 Kaikoura (New Zealand) earthquake", "author": [ { "family_name": "Hollinsworth", "given_name": "James", "orcid": "0000-0003-0122-296X", "clpid": "Hollinsworth-J" }, { "family_name": "Ye", "given_name": "Lingling", "orcid": "0000-0002-8739-2072", "clpid": "Ye-Lingling" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We investigate the Mw 7.8, 2016 Kaikoura (New Zealand) earthquake using optical satellite imagery and seismology to reveal the main features of the rupture process. Correlation of Landsat8 images reveals a 30-40\u2009km surface rupture on the Kekerengu Fault and Jordan Thrust, with up to 12\u2009m of right-lateral slip. A previously unrecognized conjugate strike-slip fault, the Papatea Fault, also slipped co-seismically (3-4\u2009m). The global CMT centroid indicates both thrust and right-lateral slip, and is located ~100\u2009km NE of the mainshock epicenter. The significant non-double-couple component of the gCMT (25%) suggests the mainshock is not well represented by a single planar fault. Back-projection of teleseismic P waves reveals two main bursts of seismic radiation: (1) at 10-20\u2009s, near the mainshock epicenter, and (2) at ~70\u2009s, close to the observed surface ruptures. We determine a finite source kinematic model of the rupture from the inversion of seismic waveforms. We use two faults in our model, defined to match the observed slip on the Kekerengu Fault, and a deeper offshore fault with a lower dip angle to satisfy the long period seismological observations. We compute the equivalent moment tensor from our finite source model and find it to be remarkably consistent with the gCMT solution. Although little is known about the geometry of these faults at depth, if the Kekerengu fault splays from the deeper thrust, it provides a rare example where the contribution of slip on a splay fault can be clearly isolated in the seismological waveforms.", "doi": "10.1002/2016GL072228", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2017-04-28", "series_number": "8", "volume": "44", "issue": "8", "pages": "3517-3525" }, { "id": "authors:27jtn-xg898", "collection": "authors", "collection_id": "27jtn-xg898", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170317-102149527", "type": "article", "title": "Rate-and-state friction properties of the Longitudinal Valley Fault from kinematic and dynamic modeling of seismic and aseismic slip", "author": [ { "family_name": "Thomas", "given_name": "Marion Y.", "orcid": "0000-0002-4335-8841", "clpid": "Thomas-M-Y" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "The Longitudinal Valley Fault (LVF, Taiwan) is a fast slipping fault (\u223c5 cm/yr), which exhibits both seismic, and aseismic slip. Geodetic and seismological observations (1992-2010) were used to infer the temporal evolution of fault slip [Thomas et al., 2014a]. This kinematic model is used here to estimate spatial variations of steady-state velocity dependence of fault friction and to develop a simplified fully-dynamic rate-and-state model of the LVF. Based on the postseismic slip, we estimate that the rate-and-state parameter (a \u2013 b) \u03c3[over-bar] decreases from \u223c1.2 MPa near the surface to near velocity-neutral at 19 km depth. The inferred (a \u2212 b) values are consistent with the laboratory measurements on clay-rich fault gouges comparable to the Lichi M\u00e9lange, which borders the LVF. The dynamic model that incorporates the obtained (a \u2013 b) \u03c3[over-bar] estimates as well as a VW patch with tuned rate-and-state properties produces a sequence of earthquakes with some realistic diversity and a spatio-temporal pattern of seismic and aseismic slip similar to that inferred from the kinematic modeling. The larger events have moment magnitude (M_w\u223c6.7) similar to the 2003 Chenkung earthquake, with a range of smaller events. The model parameterization allows reproducing partial overlap of seismic and aseismic slip before the earthquake, but cannot reproduce the significant postseismic slip observed in the previously locked patch. We discuss factors that can improve the dynamic model in that regard, including the possibility of temporal variations in (a \u2212 b) due to shear heating. Such calibrated dynamic models can be used to reconcile field observations, kinematic analysis, and laboratory experiments, and assess fault behavior.", "doi": "10.1002/2016JB013615", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2017-04", "series_number": "4", "volume": "122", "issue": "4", "pages": "3115-3137" }, { "id": "authors:75prk-hw065", "collection": "authors", "collection_id": "75prk-hw065", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170418-081344017", "type": "article", "title": "Locally and remotely triggered aseismic slip on the central San Jacinto Fault near Anza, CA, from joint inversion of seismicity and strainmeter data", "author": [ { "family_name": "Inbal", "given_name": "A.", "orcid": "0000-0001-8848-7279", "clpid": "Inbal-Asaf" }, { "family_name": "Ampuero", "given_name": "J.-P.", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We study deep aseismic slip along the central section of the San Jacinto Fault, near the Anza Seismic Gap, in southern California. Elevated strain rates following the remote M_w7.2, 4 April 2010 El Mayor-Cucapah and the local M_w5.4, 7 July 2010 Collins Valley earthquakes were recorded by Plate Boundary Observatory borehole strainmeters near Anza and were accompanied by vigorous aftershock sequences. We introduce a method to infer the distribution of triggered aseismic slip from combined seismicity and geodetic data, based on a rate-and-state friction model that maps observed changes in seismicity rates into stress changes. We invert for the cumulative slip in the 10 day period following each main shock. Synthetic tests show that the effect of aftershock interactions on the inferred slip distribution is negligible. The joint data set is more consistent with a model in which aseismic slip on a principal fault triggers seismicity on adjacent faults than with one in which aseismic slip and seismicity are coplanar. Our results indicate that aseismic slip primarily occurs along the rim of two seismicity clusters adjacent to Anza Gap, as well as beneath the Anza Gap itself, at depths larger than 10 km. The triggered aseismic slip generated by the two main shocks has little overlap, a pattern also found in sequences of large earthquakes occurring on a same fault. Stresses inferred from seismic activity leading to the Collins Valley main shock suggest that this earthquake was triggered by stresses imposed by the El Mayor-Cucapah remote-triggered aseismic slip, which persisted for more than 2 months.", "doi": "10.1002/2016JB013499", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2017-04", "series_number": "4", "volume": "122", "issue": "4", "pages": "3033-3061" }, { "id": "authors:a828a-acd46", "collection": "authors", "collection_id": "a828a-acd46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170126-133530299", "type": "article", "title": "From the seismic cycle to long-term deformation: linking seismic coupling and Quaternary coastal geomorphology along the Andean Megathrust", "author": [ { "family_name": "Saillard", "given_name": "M.", "clpid": "Saillard-M" }, { "family_name": "Audin", "given_name": "L.", "clpid": "Audin-L" }, { "family_name": "Rousset", "given_name": "B.", "clpid": "Rousset-B" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chlieh", "given_name": "M.", "clpid": "Chlieh-M" }, { "family_name": "Hall", "given_name": "S. R.", "orcid": "0000-0002-2060-7112", "clpid": "Hall-S-R" }, { "family_name": "Husson", "given_name": "L.", "clpid": "Husson-L" }, { "family_name": "Farber", "given_name": "D. L.", "clpid": "Farber-D-L" } ], "abstract": "Measurement of interseismic strain along subduction zones reveals the location of both locked asperities, which might rupture during Megathrust earthquakes, and creeping zones, which tend to arrest such seismic ruptures. The heterogeneous pattern of interseismic coupling presumably relates to spatial variations of frictional properties along the subduction interface and may also show up in the forearc morphology. To investigate this hypothesis, we compiled information on the extent of earthquake ruptures for the last 500\u2009years and uplift rates derived from dated marine terraces along the South American coastline from central Peru to Southern Chile. We additionally calculated a new interseismic coupling model for that same area based on a compilation of GPS data. We show that the coastline geometry, characterized by the distance between the coast and the trench, the latitudinal variations of long-term uplift rates and the spatial pattern of interseismic coupling are correlated. Zones of faster and long-term permanent coastal uplift, evidenced by uplifted marine terraces, coincide with peninsulas, and also with areas of creep on the megathrust where slip is mostly aseismic and tend to arrest seismic ruptures. We conclude that spatial variations of frictional properties along the megathrust dictate the tectono-geomorphological evolution of the coastal zone and the extent of seismic ruptures along strike.", "doi": "10.1002/2016TC004156", "issn": "0278-7407", "publisher": "American Geophysical Union", "publication": "Tectonics", "publication_date": "2017-02", "series_number": "2", "volume": "36", "issue": "2", "pages": "241-256" }, { "id": "authors:4k1qs-pds30", "collection": "authors", "collection_id": "4k1qs-pds30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161004-094902569", "type": "article", "title": "Autogenic entrenchment patterns and terraces due to coupling with lateral erosion in incising alluvial channels", "author": [ { "family_name": "Malatesta", "given_name": "Luca C.", "clpid": "Malatesta-L-C" }, { "family_name": "Prancevic", "given_name": "Jeffrey P.", "orcid": "0000-0003-1890-7551", "clpid": "Prancevic-J-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The abandonment of terraces in incising alluvial rivers can be used to infer tectonic and climatic histories. A river incising into alluvium erodes both vertically and laterally as it abandons fill-cut terraces. We argue that the input of sediment from the valley walls during entrenchment can alter the incision dynamics of a stream by promoting vertical incision over lateral erosion. Using a numerical model, we investigate how valley wall feedbacks may affect incision rates and terrace abandonment as the channel becomes progressively more entrenched in its valley. We postulate that erosion of taller valley walls delivers large pulses of sediment to the incising channel, potentially overwhelming the local sediment transport capacity. Based on field observations, we propose that these pulses of sediment can form talus piles that shield the valley wall from subsequent erosion and potentially force progressive channel narrowing. Our model shows that this positive feedback mechanism can enhance vertical incision relative to 1-D predictions that ignore lateral erosion. We find that incision is most significantly enhanced when sediment transport rates are low relative to the typical volume of material collapsed from the valley walls. The model also shows a systematic erosion of the youngest terraces when river incision slows down. The autogenic entrenchment due to lateral feedbacks with valley walls should be taken into account in the interpretation of complex-response terraces.", "doi": "10.1002/2015JF003797", "issn": "2169-9003", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Earth Surface", "publication_date": "2017-01", "series_number": "1", "volume": "122", "issue": "1", "pages": "335-355" }, { "id": "authors:aqkpe-py038", "collection": "authors", "collection_id": "aqkpe-py038", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170323-102209814", "type": "article", "title": "Earthquake supercycles on the Mentawai segment of the Sunda megathrust in the seventeenth century and earlier", "author": [ { "family_name": "Philibosian", "given_name": "Belle", "orcid": "0000-0003-3138-4716", "clpid": "Philibosian-B-E" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Natawidjaja", "given_name": "Danny H.", "clpid": "Natawidjaja-D-H" }, { "family_name": "Chiang", "given_name": "Hong-Wei", "clpid": "Chiang-Hong-Wei" }, { "family_name": "Wu", "given_name": "Chung-Che", "clpid": "Wu-Chung-Che" }, { "family_name": "Shen", "given_name": "Chuan-Chou", "clpid": "Shen-Chuan-Chou" }, { "family_name": "Daryono", "given_name": "Mudrik R.", "clpid": "Daryono-M-R" }, { "family_name": "Perfettini", "given_name": "Hugo", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Suwargadi", "given_name": "Bambang W.", "clpid": "Suwargadi-B-W" }, { "family_name": "Lu", "given_name": "Yanbin", "clpid": "Lu-Yanbin" }, { "family_name": "Wang", "given_name": "Xianfeng", "clpid": "Wang-Xianfeng" } ], "abstract": "Over at least the past millennium, the Mentawai segment of the Sunda megathrust has failed in sequences of closely timed events rather than in single end-to-end ruptures\u2014each the culmination of an earthquake \"supercycle.\" Here we synthesize the sixteenth- and seventeenth-century coral microatoll records into a chronology of interseismic and coseismic vertical deformation. We identify at least five discrete uplift events in about 1597, 1613, 1631, 1658, and 1703 that likely correspond to large megathrust ruptures. This sequence contrasts with the following supercycle culmination, which involved only two large ruptures in 1797 and 1833. Fault slip modeling suggests that together the five cascading ruptures involved failure of the entire Mentawai segment. Interseismic deformation rates also changed after the onset of the rupture sequence, as they did after the 1797 earthquake. We model this change as an altered distribution of fault coupling, presumably triggered by the ~1597 rupture. We also analyze the far less continuous microatoll record between A.D. 1 and 1500. While we cannot confidently delineate the extent of any megathrust rupture during that period, all evidence suggests that individual major ruptures involve only part of the Mentawai segment, often overlap below the central Mentawai Islands, often trigger coupling changes, and occur in clusters that cumulatively cover the entire Mentawai segment at the culmination of each supercycle. It is clear that each Mentawai rupture sequence evolves uniquely in terms of the order and grouping of asperities that rupture, suggesting heterogeneities in fault frictional properties at the ~100\u2009km scale.", "doi": "10.1002/2016JB013560", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2017-01", "series_number": "1", "volume": "122", "issue": "1", "pages": "642-676" }, { "id": "authors:0kfae-2px46", "collection": "authors", "collection_id": "0kfae-2px46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161017-091410617", "type": "article", "title": "The 16 April 2016, M_W 7.8 (M_S 7.5) Ecuador earthquake: A quasi-repeat of the 1942 M_S 7.5 earthquake and partial re-rupture of the 1906 M_S 8.6 Colombia\u2013Ecuador earthquake", "author": [ { "family_name": "Ye", "given_name": "Lingling", "orcid": "0000-0002-8739-2072", "clpid": "Ye-Lingling" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Li", "given_name": "Linyan", "clpid": "Li-Linyan" }, { "family_name": "Cheung", "given_name": "Kwok Fai", "orcid": "0000-0002-7435-0500", "clpid": "Cheung-Kwok-Fai" }, { "family_name": "Lay", "given_name": "Thorne", "orcid": "0000-0003-2360-4213", "clpid": "Lay-T" } ], "abstract": "The 2016 Ecuador M _W 7.8 earthquake ruptured the subduction zone boundary between the Nazca and South American plates. Joint modeling of seismic and tsunami observations indicates an \u223c120 km long rupture area beneath the coastline north of the 1998 M_W 7.2 rupture. The slip distribution reveals two discrete asperities near the hypocenter and around the equator. Their locations and the patchy pattern are consistent with the prior interseismic geodetic strain, which showed highly locked patches also beneath the coastline. Aftershocks cluster along two streaks, one aligned nearly parallel to the plate convergence direction up-dip of the main slip patches, and the other on a trench-perpendicular lineation south of the 1958 rupture zone. Comparisons of seismic waveforms and magnitudes show that the 2016 event and 1942 earthquakes have similar surface wave magnitude M_S 7.5), overlapping rupture areas, and similar main pulses of moment rate. The same area ruptured as the southernmost portion of the larger earthquake of 1906 (M_W 8.6, M_S 8.6). The seismic behavior reflects persistent heterogeneous frictional properties of the Colombia\u2013Ecuador megathrust.", "doi": "10.1016/j.epsl.2016.09.006", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2016-11-15", "volume": "454", "pages": "248-258" }, { "id": "authors:639qc-amv61", "collection": "authors", "collection_id": "639qc-amv61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161027-083345104", "type": "article", "title": "On the influence of the asthenospheric flow on the tectonics and topography at a collision-subduction transition zones: Comparison with the eastern Tibetan margin", "author": [ { "family_name": "Sternai", "given_name": "Pietro", "clpid": "Sternai-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Jolivet", "given_name": "Laurent", "clpid": "Jolivet-L" }, { "family_name": "Faccenna", "given_name": "Claudio", "clpid": "Faccenna-C" }, { "family_name": "Gerya", "given_name": "Taras", "orcid": "0000-0002-1062-2722", "clpid": "Gerya-T" }, { "family_name": "Becker", "given_name": "Thorsten Wolfgang", "clpid": "Becker-T-W" }, { "family_name": "Menant", "given_name": "Armel", "clpid": "Menant-A" } ], "abstract": "The tectonic and topographic evolution of southeast Asia is attributed to the indentation of India into Eurasia, gravitational collapse of the uplifted terrains and the dynamics of the Sunda and other western Pacific subduction zones, but their relative contributions remain elusive. Here, we analyse 3D numerical geodynamic modelling results involving a collision-subduction system and show that vigorous asthenospheric flow due to differential along-strike slab kinematics may contribute to the surface strain and elevations at collision-subduction transition zones. We argue that protracted northward migration of the collisional front and Indian slab during south to south-westward rollback subduction along the Sunda margin might have produced a similar asthenospheric flow. This flow could have contributed to the southeast Asia extrusion tectonics and uplift of the terrains around the eastern Himalayan syntaxis and protruding from southeast Tibet. Therefore, we suggest that the tectonics and topographic growth east and southeast of Tibet are controlled not only by crustal and lithospheric deformation but also by asthenospheric dynamics.", "doi": "10.1016/j.jog.2016.02.009", "issn": "0264-3707", "publisher": "Elsevier", "publication": "Journal of Geodynamics", "publication_date": "2016-10", "volume": "100", "pages": "184-197" }, { "id": "authors:k7f8a-72647", "collection": "authors", "collection_id": "k7f8a-72647", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161017-081801040", "type": "article", "title": "Time scale bias in erosion rates of glaciated landscapes", "author": [ { "family_name": "Ganti", "given_name": "Vamsi", "orcid": "0000-0003-2165-6052", "clpid": "Ganti-Vamsi" }, { "family_name": "von Hagke", "given_name": "Christoph", "orcid": "0000-0002-4386-5106", "clpid": "von-Hagke-Christoph" }, { "family_name": "Scherler", "given_name": "Dirk", "orcid": "0000-0003-3911-2803", "clpid": "Scherler-Dirk" }, { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" }, { "family_name": "Fischer", "given_name": "Woodward W.", "orcid": "0000-0002-8836-3054", "clpid": "Fischer-W-W" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time.", "doi": "10.1126/sciadv.1600204", "pmcid": "PMC5052011", "issn": "2375-2548", "publisher": "American Association for the Advancement of Science", "publication": "Science Advances", "publication_date": "2016-10", "series_number": "10", "volume": "2", "issue": "10", "pages": "Art. No. e1600204" }, { "id": "authors:tdnkx-tn611", "collection": "authors", "collection_id": "tdnkx-tn611", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160713-140842873", "type": "article", "title": "Origin and time evolution of subduction polarity reversal from plate kinematics of Southeast Asia", "author": [ { "family_name": "von Hagke", "given_name": "Christoph", "clpid": "von-Hagke-C" }, { "family_name": "Philippon", "given_name": "M\u00e9lody", "clpid": "Philippon-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Gurnis", "given_name": "Michael", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M" } ], "abstract": "We present a regional model of plate geometry and kinematics of Southeast Asia since the Late Cretaceous, embedded in a global plate model. The model involves subduction polarity reversals and sheds new light on the origin of the subduction polarity reversal currently observed in Taiwan. We show that this subduction zone reversal is inherited from subduction of the proto\u2013South China Sea plate and owes its current location to triple junction migration and slab rollback. This analysis sheds new light on the plate tectonic context of the Taiwan orogeny and questions the hypothesis that northern Taiwan can be considered an older, more mature equivalent of southern Taiwan.", "doi": "10.1130/G37821.1", "issn": "0091-7613", "publisher": "Geological Society of America", "publication": "Geology", "publication_date": "2016-08", "series_number": "8", "volume": "44", "issue": "8", "pages": "659-662" }, { "id": "authors:0n2z3-j5p90", "collection": "authors", "collection_id": "0n2z3-j5p90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160323-110329270", "type": "article", "title": "Climate-change versus landslide origin of fill terraces in a rapidly eroding bedrock landscape: San Gabriel River, California", "author": [ { "family_name": "Scherler", "given_name": "Dirk", "orcid": "0000-0003-3911-2803", "clpid": "Scherler-D" }, { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" }, { "family_name": "Rhodes", "given_name": "Edward J.", "clpid": "Rhodes-E-J" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Fill terraces along rivers represent the legacy of aggradation periods that are most commonly attributed to climate change. In the North Fork of the San Gabriel River, an arid bedrock landscape in the San Gabriel Mountains, California, a series of prominent fill terraces was previously related to climate-change\u2212induced pulses of hillslope sediment supply that temporarily and repeatedly overwhelmed river transport capacity during the Quaternary. Based on field observations, digital topographic analysis, and dating of Quaternary deposits, we suggest instead that valley aggradation was spatially confined to the North Fork San Gabriel Canyon and was a consequence of the sudden supply of unconsolidated material to upstream reaches by one of the largest known landslides in the San Gabriel Mountains. New ^(10)Be-derived surface exposure ages from the landslide deposits, previously assumed to be early to middle Pleistocene in age, indicate at least three Holocene events at ca. 8\u22129 ka, ca. 4\u22125 ka, and ca. 0.5\u22121 ka. The oldest and presumably most extensive landslide predates the valley aggradation period, which is constrained by existing ^(14)C ages and new luminescence ages to ca. 7\u22128 ka. The spatial distribution, morphology, and sedimentology of the river terraces are consistent with deposition from far-traveling debris flows that originated within, and mined, the landslide deposits. Valley aggradation in the North Fork San Gabriel Canyon therefore resulted from locally enhanced sediment supply that temporarily overwhelmed river transport capacity, but the lack of similar deposits in other parts of the San Gabriel Mountains argues against a regional climatic signal. Our study highlights the potential for valley aggradation by debris flows in arid bedrock landscapes downstream of landslides that occupy headwater areas.", "doi": "10.1130/B31356.1", "issn": "0016-7606", "publisher": "Geological Society of America", "publication": "Geological Society of America Bulletin", "publication_date": "2016-07", "series_number": "7-8", "volume": "128", "issue": "7-8", "pages": "1228-1248" }, { "id": "authors:a00b1-4mj87", "collection": "authors", "collection_id": "a00b1-4mj87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160715-080315862", "type": "article", "title": "Separating climate-induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements", "author": [ { "family_name": "Van Camp", "given_name": "M.", "clpid": "Van-Camp-M" }, { "family_name": "de Viron", "given_name": "O.", "clpid": "de-Viron-O" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We estimate the signature of the climate-induced mass transfers in repeated absolute gravity measurements based on satellite gravimetric measurements from the Gravity Recovery and Climate Experiment (GRACE) mission. We show results at the globe scale and compare them with repeated absolute gravity (AG) time behavior in three zones where AG surveys have been published: Northwestern Europe, Canada, and Tibet. For 10 yearly campaigns, the uncertainties affecting the determination of a linear gravity rate of change range 3\u20134\u2009nm/s^2/a in most cases, in the absence of instrumental artifacts. The results are consistent with what is observed for long-term repeated campaigns. We also discuss the possible artifact that can result from using short AG survey to determine the tectonic effects in a zone of high hydrological variability. We call into question the tectonic interpretation of several gravity changes reported from stations in Tibet, in particular the variation observed prior to the 2015 Gorkha earthquake.", "doi": "10.1002/2016GL068648", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2016-05-16", "series_number": "9", "volume": "43", "issue": "9", "pages": "4313-4320" }, { "id": "authors:sb92a-ssq81", "collection": "authors", "collection_id": "sb92a-ssq81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160909-095219599", "type": "article", "title": "Postseismic relocking of the subduction megathrust following the 2007 Pisco, Peru, earthquake", "author": [ { "family_name": "Remy", "given_name": "D.", "clpid": "Remy-D" }, { "family_name": "Perfettini", "given_name": "H.", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Cotte", "given_name": "N.", "orcid": "0000-0002-1596-0755", "clpid": "Cotte-N" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chlieh", "given_name": "M.", "clpid": "Chlieh-M" }, { "family_name": "Bondoux", "given_name": "F.", "clpid": "Bondoux-F" }, { "family_name": "Sladen", "given_name": "A.", "orcid": "0000-0003-4126-0020", "clpid": "Sladen-A" }, { "family_name": "Tavera", "given_name": "H.", "clpid": "Tavera-H" }, { "family_name": "Socquet", "given_name": "A.", "clpid": "Socquet-A" } ], "abstract": "Characterizing the time evolution of slip over different phases of the seismic cycle is crucial to a better understanding of the factors controlling the occurrence of large earthquakes. In this study, we take advantage of interferometric synthetic aperture radar data and 3.5\u2009years of continuous Global Positioning System (GPS) measurements to determine interseismic, coseismic, and postseismic slip distributions in the region of the 2007, M_w 8.0 Pisco, earthquake, Peru, using the same fault geometry and inversion method. Our interseismic model, based on pre-2007 campaign GPS data, suggests that the 2007 Pisco seismic slip occurred in a region strongly coupled before the earthquake while afterslip occurred in low coupled regions. Large afterslip occurred in the peripheral area of coseismic rupture in agreement with the notion that afterslip is mainly induced by coseismic stress changes. The temporal evolution of the region of maximum afterslip, characterized by a relaxation time of about 2.3\u2009years, is located in the region where the Nazca ridge is subducting, consistent with rate-strengthening friction promoting aseismic slip. We estimate a return period for the Pisco earthquake of about 230\u2009years with an estimated aseismic slip that might account for about 50% of the slip budget in this region over the 0\u201350\u2009km seismogenic depth range. A major result of this study is that the main asperity that ruptured during the 2007 Pisco earthquake relocked soon after this event.", "doi": "10.1002/2015JB012417", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2016-05", "series_number": "5", "volume": "121", "issue": "5", "pages": "3978-3995" }, { "id": "authors:yeskv-a8d93", "collection": "authors", "collection_id": "yeskv-a8d93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160407-155935752", "type": "article", "title": "Millenary M_w > 9.0 earthquakes required by geodetic strain in the Himalaya", "author": [ { "family_name": "Stevens", "given_name": "V. L.", "clpid": "Stevens-V-L" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The Himalayan arc produced the largest known continental earthquake, the M_w\u2009\u2248\u20098.7 Assam earthquake of 1950, but how frequently and where else in the Himalaya such large-magnitude earthquakes occur is not known. Paleoseismic evidence for coseismic ruptures at the front of the Himalaya with 15 to 30\u2009m of slip suggests even larger events in medieval times, but this inference is debated. Here we estimate the frequency and magnitude of the largest earthquake in the Himalaya needed so that the moment released by seismicity balances the deficit of moment derived from measurements of geodetic strain. Assuming one third of the moment buildup is released aseismically and the earthquakes roughly follow a Gutenberg-Richter distribution, we find that M_w\u2009>\u20099.0 events are needed with a confidence level of at least 60% and must return approximately once per 800\u2009years on average.", "doi": "10.1002/2015GL067336", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2016-02-16", "series_number": "3", "volume": "43", "issue": "3", "pages": "1118-1123" }, { "id": "authors:hwk94-8y960", "collection": "authors", "collection_id": "hwk94-8y960", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160225-105620266", "type": "article", "title": "Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake", "author": [ { "family_name": "Elliott", "given_name": "J. R.", "clpid": "Elliott-J-R" }, { "family_name": "Jolivet", "given_name": "R.", "orcid": "0000-0002-9896-3651", "clpid": "Jolivet-R" }, { "family_name": "Gonz\u00e1lez", "given_name": "P. J.", "clpid": "Gonz\u00e1lez-P-J" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hollingsworth", "given_name": "J.", "orcid": "0000-0003-0122-296X", "clpid": "Hollingsworth-J" }, { "family_name": "Searle", "given_name": "M. P.", "clpid": "Searle-M-P" }, { "family_name": "Stevens", "given_name": "V. L.", "clpid": "Stevens-V-L" } ], "abstract": "The Himalayan mountain range has been the locus of some of the largest continental earthquakes, including the 2015 magnitude 7.8 Gorkha earthquake. Competing hypotheses suggest that Himalayan topography is sustained and plate convergence is accommodated either predominantly on the main plate boundary fault, or more broadly across multiple smaller thrust faults. Here we use geodetic measurements of surface displacement to show that the Gorkha earthquake ruptured the Main Himalayan Thrust fault. The earthquake generated about 1\u2009m of uplift in the Kathmandu Basin, yet caused the high Himalaya farther north to subside by about 0.6\u2009m. We use the geodetic data, combined with geologic, geomorphological and geophysical analyses, to constrain the geometry of the Main Himalayan Thrust in the Kathmandu area. Structural analyses together with interseismic and coseismic displacements are best explained by a steep, shallow thrust fault flattening at depth between 5 and 15\u2009km and connecting to a mid-crustal, steeper thrust. We suggest that present-day convergence across the Himalaya is mostly accommodated by this fault\u2014no significant motion on smaller thrust faults is required. Furthermore, given that the Gorkha earthquake caused the high Himalayan mountains to subside and that our fault geometry explains measured interseismic displacements, we propose that growth of Himalayan topography may largely occur during the ongoing post-seismic phase.", "doi": "10.1038/ngeo2623", "issn": "1752-0894", "publisher": "Nature Publishing Group", "publication": "Nature Geoscience", "publication_date": "2016-02", "series_number": "2", "volume": "9", "issue": "2", "pages": "174-180" }, { "id": "authors:cjtr2-6e496", "collection": "authors", "collection_id": "cjtr2-6e496", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160401-080805516", "type": "article", "title": "The influence of stress history on the grain size and microstructure of experimentally deformed quartzite", "author": [ { "family_name": "Kidder", "given_name": "Steven", "clpid": "Kidder-S-B" }, { "family_name": "Hirth", "given_name": "Greg", "clpid": "Hirth-G" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Behr", "given_name": "Whitney", "clpid": "Behr-W" } ], "abstract": "Deformation of middle crustal shear zones likely varies with time as a result of the stress build-up and release associated with earthquakes and post-seismic deformation, but the processes involved and their microstructural signature in the rock record are poorly understood. We conducted a series of experiments on quartzite at 900 \u00b0C to characterize microstructures associated with changes in stress and strain rate, and to investigate the feasibility of carrying out grain size piezometry in natural rocks that experienced analogous changes. Differential stress (referred to simply as \"stress\") was varied in two-stage experiments by changing strain rate and by stopping the motor and allowing stress to relax. The two-stage samples preserve a microstructural record that can be interpreted quantitatively in terms of stress history. The microstructure associated with a stress increase is a bimodal distribution of recrystallized grain sizes. The smaller grains associated with the second deformation stage accurately record the stress of the second stage, and the surviving coarse grains remain similar in size to those formed during the earlier stage. The transient microstructure associated with stress decrease is a \"partial foam\" texture containing a larger concentration of stable 120\u00b0 triple junctions than occur in samples deformed at a relatively constant strain rate. Our results indicate that microstructures preserved in rocks that experienced relatively simple, two-stage deformation histories can be used to quantitatively assess stress histories.\n\nGrain growth rates during deformation are similar to rates observed in previous isostatic growth experiments, supporting theoretical approaches to recrystallized grain size, such as the wattmeter theory (Austin and Evans, 2007), that incorporate static growth rates. From an analysis of the experimental data for quartz recrystallized grain size, we find: 1) Recrystallized grain size quickly reaches a value consistent with ambient deformation conditions. We argue that this explains a good match between average grain sizes predicted by the wattmeter after complete recrystallization and the recrystallized grain sizes of the experiments. 2) The present formulation of the wattmeter overestimates the rates at which porphyroclasts recrystallize by as much as an order of magnitude, and 3) owing to problems with extrapolation of grain growth data for quartz, the wattmeter is not presently applicable to natural samples deformed at low temperatures. We present a simplified flow law for quartz, and suggest that the change in slope of the quartz piezometer at high stress (regime 1) is related to a switch to a linear viscous rheology.", "doi": "10.1016/j.jsg.2015.12.004", "issn": "0191-8141", "publisher": "Elsevier", "publication": "Journal of Structural Geology", "publication_date": "2016-02", "volume": "83", "pages": "194-206" }, { "id": "authors:k1fxk-f5735", "collection": "authors", "collection_id": "k1fxk-f5735", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150929-080354449", "type": "article", "title": "Erosion by an Alpine glacier", "author": [ { "family_name": "Herman", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Herman-F" }, { "family_name": "Beyssac", "given_name": "Olivier", "clpid": "Beyssac-O" }, { "family_name": "Brughelli", "given_name": "Mattia", "clpid": "Brughelli-M" }, { "family_name": "Lane", "given_name": "Stuart N.", "clpid": "Lane-S-N" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Adatte", "given_name": "Thierry", "clpid": "Adatte-T" }, { "family_name": "Lin", "given_name": "Jiao Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Cox", "given_name": "Simon C.", "clpid": "Cox-S-C" } ], "abstract": "Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.", "doi": "10.1126/science.aab2386", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2015-10-09", "series_number": "6257", "volume": "350", "issue": "6257", "pages": "193-195" }, { "id": "authors:qhk0h-nz521", "collection": "authors", "collection_id": "qhk0h-nz521", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150721-170858547", "type": "article", "title": "Slip pulse and resonance of the Kathmandu basin during the 2015 Gorkha earthquake, Nepal", "author": [ { "family_name": "Galetzka", "given_name": "J.", "clpid": "Galetzka-J" }, { "family_name": "Genrich", "given_name": "J. F.", "clpid": "Genrich-J-F" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hudnut", "given_name": "K. W.", "orcid": "0000-0002-3168-4797", "clpid": "Hudnut-K-W" } ], "abstract": "Detailed geodetic imaging of earthquake ruptures enhances our understanding of earthquake physics and associated ground shaking. The 25 April 2015 moment magnitude 7.8 earthquake in Gorkha, Nepal was the first large continental megathrust rupture to have occurred beneath a high-rate (5-hertz) Global Positioning System (GPS) network. We used GPS and interferometric synthetic aperture radar data to model the earthquake rupture as a slip pulse ~20 kilometers in width, ~6 seconds in duration, and with a peak sliding velocity of 1.1 meters per second, which propagated toward the Kathmandu basin at ~3.3 kilometers per second over ~140 kilometers. The smooth slip onset, indicating a large (~5-meter) slip-weakening distance, caused moderate ground shaking at high frequencies (>1 hertz; peak ground acceleration, ~16% of Earth's gravity) and minimized damage to vernacular dwellings. Whole-basin resonance at a period of 4 to 5 seconds caused the collapse of tall structures, including cultural artifacts.", "doi": "10.1126/science.aac6383", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2015-09-04", "series_number": "6252", "volume": "349", "issue": "6252", "pages": "1091-1095" }, { "id": "authors:rs837-eaj64", "collection": "authors", "collection_id": "rs837-eaj64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150721-143815662", "type": "article", "title": "Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Meng", "given_name": "Lingsen", "orcid": "0000-0003-2428-0548", "clpid": "Meng-Lingsen" }, { "family_name": "Wei", "given_name": "Shengji", "clpid": "Wei-Shengji" }, { "family_name": "Wang", "given_name": "Teng", "clpid": "Wang-Teng" }, { "family_name": "Ampuero", "given_name": "Jean-Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" } ], "abstract": "Large earthquakes are thought to release strain on previously locked faults. However, the details of how earthquakes are initiated, grow and terminate in relation to pre-seismically locked and creeping patches is unclear. The 2015 M_w 7.8 Gorkha, Nepal earthquake occurred close to Kathmandu in a region where the prior pattern of fault locking is well documented. Here we analyse this event using seismological records measured at teleseismic distances and Synthetic Aperture Radar imagery. We show that the earthquake originated northwest of Kathmandu within a cluster of background seismicity that fringes the bottom of the locked portion of the Main Himalayan Thrust fault (MHT). The rupture propagated eastwards for about 140\u2009km, unzipping the lower edge of the locked portion of the fault. High-frequency seismic waves radiated continuously as the slip pulse propagated at about 2.8\u2009km\u2009s^(\u22121) along this zone of presumably high and heterogeneous pre-seismic stress at the seismic\u2013aseismic transition. Eastward unzipping of the fault resumed during the M_w 7.3 aftershock on 12 May. The transfer of stress to neighbouring regions during the Gorkha earthquake should facilitate future rupture of the areas of the MHT adjacent and updip of the Gorkha earthquake rupture.", "doi": "10.1038/ngeo2518", "issn": "1752-0894", "publisher": "Nature Publishing Group", "publication": "Nature Geoscience", "publication_date": "2015-09", "series_number": "9", "volume": "8", "issue": "9", "pages": "708-711" }, { "id": "authors:q3fpn-0h047", "collection": "authors", "collection_id": "q3fpn-0h047", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150910-134543395", "type": "article", "title": "Response to Comment on \"Tectonic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet\"", "author": [ { "family_name": "Wang", "given_name": "Ping", "clpid": "Wang-Ping" }, { "family_name": "Scherler", "given_name": "Dirk", "orcid": "0000-0003-3911-2803", "clpid": "Scherler-D" }, { "family_name": "Liu-Zeng", "given_name": "Jing", "clpid": "Liu-Zeng-Jing" }, { "family_name": "Mey", "given_name": "J\u00fcrgen", "clpid": "Mey-J" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Zhang", "given_name": "Yunda", "clpid": "Zhang-Yunda" }, { "family_name": "Shi", "given_name": "Dingguo", "clpid": "Shi-Dingguo" } ], "abstract": "In their Comment, Zeitler et al. do not challenge our results or interpretation. Our study does not disprove coupling between tectonic uplift and erosion but suggests that this coupling cannot be the sole explanation of rapid uplift in the Himalayan syntaxes.", "doi": "10.1126/science.aaa9636", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2015-08-21", "series_number": "6250", "volume": "349", "issue": "6250", "pages": "799-799" }, { "id": "authors:7qgcw-dkb40", "collection": "authors", "collection_id": "7qgcw-dkb40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150903-124854490", "type": "article", "title": "Interseismic coupling on the main Himalayan thrust", "author": [ { "family_name": "Stevens", "given_name": "V. L.", "clpid": "Stevens-V-L" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We determine the slip rate and pattern of interseismic coupling on the Main Himalayan Thrust along the entire Himalayan arc based on a compilation of geodetic, interferometric synthetic aperture radar, and microseismicity data. We show that convergence is perpendicular to the arc and increases eastwards from 13.3 \u00b1 1.7 mm/yr to 21.2 \u00b1 2.0 mm/yr. These rates are comparable to geological and geomorphic estimates, indicating an essentially elastic geodetic surface strain. The interseismic uplift rate predicted from the coupling model closely mimics the topography, suggesting that a small percentage of the interseismic strain is permanent. We find that the fault is fully locked along its complete length over about 100 km width. We don't find any resolvable aseismic barrier that could affect the seismic segmentation of the arc and limit the along-strike propagation of seismic ruptures. The moment deficit builds up at a rate of 15.1 \u00b1 1 \u00d7 10^(19) N m/yr for the entire length of the Himalaya.", "doi": "10.1002/2015GL064845", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2015-07-28", "series_number": "14", "volume": "42", "issue": "14", "pages": "5828-5837" }, { "id": "authors:qt3cj-11b27", "collection": "authors", "collection_id": "qt3cj-11b27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150429-104726958", "type": "article", "title": "The 2012 Brawley swarm triggered by injection-induced aseismic slip", "author": [ { "family_name": "Wei", "given_name": "Shengji", "clpid": "Wei-Shengji" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hudnut", "given_name": "Kenneth W.", "orcid": "0000-0002-3168-4797", "clpid": "Hudnut-K-W" }, { "family_name": "Donnellan", "given_name": "Andrea", "clpid": "Donnellan-A" }, { "family_name": "Parker", "given_name": "Jay W.", "clpid": "Parker-J-W" }, { "family_name": "Graves", "given_name": "Robert W.", "clpid": "Graves-R-W" }, { "family_name": "Helmberger", "given_name": "Don", "clpid": "Helmberger-D-V" }, { "family_name": "Fielding", "given_name": "Eric", "orcid": "0000-0002-6648-8067", "clpid": "Fielding-E-J" }, { "family_name": "Liu", "given_name": "Zhen", "orcid": "0000-0002-6313-823X", "clpid": "Liu-Zhen" }, { "family_name": "Cappa", "given_name": "Frederic", "orcid": "0000-0003-4859-8024", "clpid": "Cappa-F" }, { "family_name": "Eneva", "given_name": "Mariana", "clpid": "Eneva-M" } ], "abstract": "It has long been known that fluid injection or withdrawal can induce earthquakes, but the underlying mechanisms remain elusive. For example, the 2012 Brawley swarm, which produced two strike-slip shocks with magnitudes larger than 5.3 and surface ruptures in the close vicinity of a geothermal field, started with earthquakes about 5 km deeper than the injection depth (\u223c1.5 km). This makes the causality between the injection and seismicity unclear. Here, we jointly analyze broadband and strong motion waveforms, UAVSAR, leveling measurements and field observations to reveal the detailed seismic and aseismic faulting behaviors associated with the 2012 Brawley swarm. In particular, path calibration established from smaller events in the swarm allows waveform inversion to be conducted up to 3 Hz to resolve finite rupture process of the Mw 4.7 normal event. Our results show that the 2012 earthquake sequence was preceded by aseismic slip on a shallow normal fault beneath the geothermal field. Aseismic slip initiated in 2010 when injection rate rapidly increased and triggered the following earthquakes subsequently, including unusually shallow and relatively high frequency seismic excitations on the normal fault. In this example, seismicity is induced indirectly by fluid injection, a result of mediation by aseismic creep, rather than directly by a pore pressure increase at the location of the earthquakes.", "doi": "10.1016/j.epsl.2015.03.054", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2015-07-15", "volume": "422", "pages": "115-125" }, { "id": "authors:paq0w-1qz88", "collection": "authors", "collection_id": "paq0w-1qz88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150611-110529655", "type": "article", "title": "Seismicity triggered by fluid injection\u2013induced aseismic slip", "author": [ { "family_name": "Guglielmi", "given_name": "Yves", "orcid": "0000-0001-9581-7475", "clpid": "Guglielmi-Y" }, { "family_name": "Cappa", "given_name": "Fr\u00e9d\u00e9ric", "orcid": "0000-0003-4859-8024", "clpid": "Cappa-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Henry", "given_name": "Pierre", "clpid": "Henry-P" }, { "family_name": "Elsworth", "given_name": "Derek", "orcid": "0000-0002-4942-1151", "clpid": "Elsworth-D" } ], "abstract": "Anthropogenic fluid injections are known to induce earthquakes. The mechanisms involved are\npoorly understood, and our ability to assess the seismic hazard associated with geothermal\nenergy or unconventional hydrocarbon production remains limited. We directly measure fault\nslip and seismicity induced by fluid injection into a natural fault. We observe highly dilatant\nand slow [~4 micrometers per second (\u00b5m/s)] aseismic slip associated with a 20-fold increase\nof permeability, which transitions to faster slip (~10 \u00b5m/s) associated with reduced dilatancy\nand micro-earthquakes. Most aseismic slip occurs within the fluid-pressurized zone and obeys\na rate-strengthening friction law \u00b5 = 0.67 + 0.045ln (v/v_0) with v_0 = 0.1 \u00b5m/s. Fluid injection\nprimarily triggers aseismic slip in this experiment, with micro-earthquakes being an indirect\neffect mediated by aseismic creep.", "doi": "10.1126/science.aab0476", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2015-06-12", "series_number": "6240", "volume": "348", "issue": "6240", "pages": "1224-1226" }, { "id": "authors:e5v37-h6325", "collection": "authors", "collection_id": "e5v37-h6325", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150416-154546979", "type": "article", "title": "Numerical modeling of long-term earthquake sequences on the NE Japan megathrust: Comparison with observations and implications for fault friction", "author": [ { "family_name": "Cubas", "given_name": "Nadaya", "clpid": "Cubas-N" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Perfettini", "given_name": "Hugo", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" } ], "abstract": "We use numerical modeling to investigate fault properties that explain key features of the 2011 Mw 9.0 Tohoku-Oki earthquake as well as the overall regional behavior of the NE Japan megathrust. In particular, we study the possibility that slip near the trench resulted from thermal pressurization on a shallow patch of the megathrust, and investigate whether low-velocity friction on that patch is rate-strengthening or rate-weakening. Our models also contain a deeper rate-weakening patch, not prone to efficient thermal pressurization, to account for the moderate-sized interplate seismicity. We produce earthquake sequences and aseismic slip in our models using 2D dynamic simulations that incorporate shear-induced temperature variations and the associated change in pore fluid pressure to capture thermal pressurization. We find that all our models can reproduce more frequent deeper moderate (Mw 7.5) events and less frequent larger events with substantial slip at shallow depth, as observed along the Fukushima\u2013Miyagi segment of the Japan megathrust. However, only the scenario with a sufficiently rate-strengthening patch can match the thousand-year recurrence time of Tohoku-Oki-like earthquakes suggested by the historical and geological record, due to co-existence of seismic and aseismic slip at the shallow depths. This scenario also reproduces other characteristics of the Tohoku-Oki earthquake: the trenchward-skewed distribution of slip, the backward re-rupture of the deeper patch, as well as the weaker radiation at high frequency of the shallower portion of the rupture in spite of its larger slip.", "doi": "10.1016/j.epsl.2015.03.002", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2015-06-01", "volume": "419", "pages": "187-198" }, { "id": "authors:cfjva-1dj35", "collection": "authors", "collection_id": "cfjva-1dj35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150430-091229989", "type": "article", "title": "Postseismic Deformation Following the 2010 M=7.2 El Mayor-Cucapah Earthquake: Observations, Kinematic Inversions, and Dynamic Models", "author": [ { "family_name": "Rollins", "given_name": "Christopher", "orcid": "0000-0002-5291-6956", "clpid": "Rollins-C" }, { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Due to its location on a transtensional section of the Pacific-North American plate boundary, the Salton Trough is a region featuring large strike-slip earthquakes within a regime of shallow asthenosphere, high heat flow, and complex faulting, and so postseismic deformation there may feature enhanced viscoelastic relaxation and afterslip that is particularly detectable at the surface. The 2010 M=7.2 El Mayor-Cucapah earthquake was the largest shock in the Salton Trough since 1892 and occurred close to the US-Mexico border, and so the postseismic deformation recorded by the continuous GPS network of southern California provides an opportunity to study the rheology of this region. Three-year postseismic transients extracted from GPS displacement time-series show four key features: (1) 1\u20132 cm of cumulative uplift in the Imperial Valley and \u223c 1 cm of subsidence in the Peninsular Ranges, (2) relatively large cumulative horizontal displacements > 150 km from the rupture in the Peninsular Ranges, (3) rapidly decaying horizontal displacement rates in the first few months after the earthquake in the Imperial Valley, and (4) sustained horizontal velocities, following the rapid early motions, that were still visibly ongoing 3 years after the earthquake. Kinematic inversions show that the cumulative 3-year postseismic displacement field can be well fit by afterslip on and below the coseismic rupture, though these solutions require afterslip with a total moment equivalent to at least a M=7.2 earthquake and higher slip magnitudes than those predicted by coseismic stress changes. Forward modeling shows that stress-driven afterslip and viscoelastic relaxation in various configurations within the lithosphere can reproduce the early and later horizontal velocities in the Imperial Valley, while Newtonian viscoelastic relaxation in the asthenosphere can reproduce the uplift in the Imperial Valley and the subsidence and large westward displacements in the Peninsular Ranges. We present two forward models of dynamically coupled deformation mechanisms that fit the postseismic transient well: a model combining afterslip in the lower crust, Newtonian viscoelastic relaxation in a localized zone in the lower crust beneath areas of high heat flow and geothermal activity, and Newtonian viscoelastic relaxation in the asthenosphere; and a second model that replaces the afterslip in the first model with viscoelastic relaxation with a stress-dependent viscosity in the mantle. The rheology of this high-heat-flow, high-strain-rate region may incorporate elements of both these models and may well be more complex than either of them.", "doi": "10.1007/s00024-014-1005-6", "issn": "0033-4553", "publisher": "Springer", "publication": "Pure and Applied Geophysics", "publication_date": "2015-05", "series_number": "5", "volume": "172", "issue": "5", "pages": "1305-1358" }, { "id": "authors:fcdba-ht686", "collection": "authors", "collection_id": "fcdba-ht686", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150402-135439354", "type": "article", "title": "Static Laboratory Earthquake Measurements with the Digital Image Correlation Method", "author": [ { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-V" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Leprince", "given_name": "S.", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Mapping full-field displacement and strain changes on the Earth's surface following an earthquake is of paramount importance to enhance our understanding of earthquake mechanics. Currently, aerial and satellite images taken pre- and post-earthquake can be processed with sub-pixel correlation algorithms to infer the co-seismic ground deformations (e.g., [1, 2]). However, the interpretation of this data is not straightforward due to the inherent complexity of natural faults and deformation fields. To gain understanding into rupture mechanics and to help interpret complex rupture features occurring in nature, we develop a laboratory earthquake setup capable of reproducing displacement and strain maps similar to those obtained in the field, while maintaining enough simplicity so that clear conclusions can be drawn. Earthquakes are mimicked in the laboratory by dynamic rupture propagating along an inclined frictional interface formed by two Homalite plates under compression (e.g., [3]). In our study, the interface is partially glued, in order to confine the rupture before it reaches the ends of the specimen. The specimens are painted with a speckle pattern to provide the surface with characteristic features for image matching. Images of the specimens are taken before and after dynamic rupture with a 4 Megapixels resolution CCD camera. The digital images are analyzed with two software packages for sub-pixel correlation: VIC-2D (Correlated Solutions Inc.) and COSI-Corr. Both VIC-2D and COSI-Corr are able to characterize the full-field static displacement of the experimentally produced dynamic shear ruptures. The correlation analysis performed with either software clearly shows (i) the relative displacement (slip) along the frictional interface, (ii) the rupture arrest on the glued boundaries, and (iii) the presence of wing cracks. The obtained displacement measurements are converted to strains, using non-local de-noising techniques; stresses are obtained by introducing Homalite's constitutive properties. This study is a first step towards using the digital image correlation method in combination with high-speed photography to capture the highly transient phenomena involved in dynamic rupture.", "doi": "10.1007/s11340-014-9893-z", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2015-01", "series_number": "1", "volume": "55", "issue": "1", "pages": "77-94" }, { "id": "authors:hbjnf-yh796", "collection": "authors", "collection_id": "hbjnf-yh796", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141002-110016774", "type": "article", "title": "Tectonic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet", "author": [ { "family_name": "Wang", "given_name": "Ping", "clpid": "Wang-Ping" }, { "family_name": "Scherler", "given_name": "Dirk", "orcid": "0000-0003-3911-2803", "clpid": "Scherler-D" }, { "family_name": "Liu-Zeng", "given_name": "Jing", "clpid": "Liu-Zeng-J" }, { "family_name": "Mey", "given_name": "J\u00fcrgen", "clpid": "Mey-J" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Zhang", "given_name": "Yunda", "clpid": "Zhang-Yunda" }, { "family_name": "Shi", "given_name": "Dingguo", "clpid": "Shi-Dingguo" } ], "abstract": "The Himalayan mountains are dissected by some of the deepest and most impressive gorges on Earth. Constraining the interplay between river incision and rock uplift is important for understanding tectonic deformation in this region. We report here the discovery of a deeply incised canyon of the Yarlung Tsangpo River, at the eastern end of the Himalaya, which is now buried under more than 500 meters of sediments. By reconstructing the former valley bottom and dating sediments at the base of the valley fill, we show that steepening of the Tsangpo Gorge started at about 2 million to 2.5 million years ago as a consequence of an increase in rock uplift rates. The high erosion rates within the gorge are therefore a direct consequence of rapid rock uplift.", "doi": "10.1126/science.1259041", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2014-11-21", "series_number": "6212", "volume": "346", "issue": "6212", "pages": "978-981" }, { "id": "authors:88xry-bjt60", "collection": "authors", "collection_id": "88xry-bjt60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140828-133117445", "type": "article", "title": "Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux", "author": [ { "family_name": "Ayoub", "given_name": "F.", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Newman", "given_name": "C. E.", "clpid": "Newman-C-E" }, { "family_name": "Richardson", "given_name": "M. I.", "clpid": "Richardson-M-I" }, { "family_name": "Lucas", "given_name": "A.", "clpid": "Lucas-A" }, { "family_name": "Leprince", "given_name": "S.", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Bridges", "given_name": "N. T.", "orcid": "0000-0002-6790-6793", "clpid": "Bridges-N-T" } ], "abstract": "Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1\u2013100\u2009km scale) of T_s=0.01\u00b10.0015\u2009N\u2009m^(\u22122).", "doi": "10.1038/ncomms6096", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2014-09-30", "volume": "5", "pages": "Art. no. 5096" }, { "id": "authors:kb670-bp502", "collection": "authors", "collection_id": "kb670-bp502", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141121-083842997", "type": "article", "title": "Lithological control on the deformation mechanism and the mode of fault slip on the Longitudinal Valley Fault, Taiwan", "author": [ { "family_name": "Thomas", "given_name": "Marion Y.", "orcid": "0000-0002-4335-8841", "clpid": "Thomas-M-Y" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Gratier", "given_name": "Jean-Pierre", "clpid": "Gratier-J-P" }, { "family_name": "Lee", "given_name": "Jian-Cheng", "clpid": "Lee-Jian-Cheng" } ], "abstract": "The Longitudinal Valley Fault (LVF) in Taiwan is creeping at shallow depth along its southern half, where it is bounded by the Lichi M\u00e9lange. By contrast, the northern segment of the LVF is locked where it is bounded by forearc sedimentary and volcanoclastic formations. Structural and petrographic investigations show that the Lichi M\u00e9lange most probably formed as a result of internal deformation of the forearc when the continental shelf of South China collided with the Luzon arc as a result of the subduction of the South China Sea beneath the Philippine Sea Plate. The forearc formations constitute the protolith of the Lichi M\u00e9lange. It seems improbable that the mechanical properties of the minerals of the matrix (illite, chorite, kaolinite) in themselves explain the aseismic behavior of the LVF. Microstructural investigations show that deformation within the fault zone must have resulted from a combination of frictional sliding at grain boundaries, cataclasis (responsible for grain size comminution) and pressure solution creep (responsible for the development of the scaly foliation and favored by the mixing of soluble and insoluble minerals). The microstructure of the gouge formed in the Lichi M\u00e9lange favors effective pressure solution creep, which inhibits strain-weakening brittle mechanisms and is probably responsible for the dominantly aseismic mode of fault slip. Since the Lichi M\u00e9lange is analogous to any unlithified subduction m\u00e9langes, this study sheds light on the mechanisms which favor aseismic creep on subduction megathrust.", "doi": "10.1016/j.tecto.2014.05.038", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2014-09-29", "volume": "632", "pages": "48-63" }, { "id": "authors:ncwa0-zv610", "collection": "authors", "collection_id": "ncwa0-zv610", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141202-105757792", "type": "article", "title": "Rupture and variable coupling behavior of the Mentawai segment of the Sunda megathrust during the supercycle culmination of 1797 to 1833", "author": [ { "family_name": "Philibosian", "given_name": "Belle", "orcid": "0000-0003-3138-4716", "clpid": "Philibosian-B-E" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Natawidjaja", "given_name": "Danny H.", "clpid": "Natawidjaja-D-H" }, { "family_name": "Chiang", "given_name": "Hong-Wei", "clpid": "Chiang-Hong-Wei" }, { "family_name": "Wu", "given_name": "Chung-Che", "clpid": "Wu-Chung-Che" }, { "family_name": "Perfettini", "given_name": "Hugo", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Shen", "given_name": "Chuan-Chou", "clpid": "Shen-Chuan-Chou" }, { "family_name": "Daryono", "given_name": "Mudrik R.", "clpid": "Daryono-M-R" }, { "family_name": "Suwargadi", "given_name": "Bambang W.", "clpid": "Suwargadi-B-W" } ], "abstract": "We refer to periods of subduction strain accumulation beneath the Mentawai Islands, Sumatra, as \"supercycles,\" because each culminates in a series of partial ruptures of the megathrust in its final decades. The finale of the previous supercycle comprised two giant earthquakes in 1797 and 1833 and whatever happened in between. This behavior between two great ruptures has implications for how the megathrust will behave between its more recent partial failure, during the M_w 8.4 earthquake of 2007, and subsequent large ruptures. We synthesize previously published coral microatoll records and a large new coral data set to constrain not only these two giant ruptures but also the intervening interseismic megathrust behavior. We present detailed maps of coseismic uplift during the two earthquakes and of interseismic deformation during the periods 1755\u20131833 and 1950\u20132000, as well as models of the corresponding slip and coupling on the underlying megathrust. The large magnitudes we derive (M_w 8.6\u20138.8 for 1797 and M_w 8.8\u20138.9 for 1833) confirm that the 2007 earthquakes released only a fraction of the moment released during the previous rupture sequence. Whereas megathrust behavior leading up to the 1797 and 2007 earthquakes was similar and comparatively simple, behavior between 1797 and 1833 was markedly different and more complex: several patches of the megathrust became weakly coupled following the 1797 earthquake. We conclude that while major earthquakes generally do not involve rupture of the entire Mentawai segment, they may significantly change the state of coupling on the megathrust for decades to follow, influencing the progression of subsequent ruptures.", "doi": "10.1002/2014JB011200", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2014-09", "series_number": "9", "volume": "119", "issue": "9", "pages": "7258-7287" }, { "id": "authors:23djw-hrq80", "collection": "authors", "collection_id": "23djw-hrq80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140828-112246557", "type": "article", "title": "Response of rate-and-state seismogenic faults to harmonic shear-stress perturbations", "author": [ { "family_name": "Ader", "given_name": "Thomas J.", "clpid": "Ader-T-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ampuero", "given_name": "Jean-Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" } ], "abstract": "Field and laboratory observations show that seismicity has non-trivial period-dependent response to periodic stress perturbations. In Nepal, seismicity shows significant variations in response to annual monsoon-induced stress variations but not to semidiurnal tidal stresses of the same magnitude. Such period dependence cannot be explained by the Coulomb failure model and spring-slider rate-and-state model (SRM). Here, we study seismicity response to periodic stress perturbations in a 2-D continuum model of a rate-and-state fault (that is, a finite rate-and-state fault). We find that the resulting seismicity indeed exhibits nearly periodic variations. Their amplitude is maximum at a certain period, T_a, and decreases with smaller and larger periods to the SRM predictions, remaining much larger than the SRM predictions for a wide range of periods around T_a. We attribute the higher sensitivity of finite faults to their finite nucleation zones which vary in space and have a different slip-velocity evolution than that of the SRM. At periods T \u226b T_a and T \u226a T_a, the seismicity-rate variations are in phase with the stress-rate and stress variations, respectively, consistent with the SRM, although a gradual phase shift appears as T increases towards T_a. Based on the similarities with the SRM and our simulations, we propose a semi-analytical expression for T_a. Plausible sets of model parameters make T_a equal to 1\u2009yr, potentially explaining Nepal observations and constraining the fault properties. Our finite-fault findings indicate that a\u03c3, where a is a rate-and-state parameter and \u03c3 is the effective normal stress, can be severely underestimated based on the SRM.", "doi": "10.1093/gji/ggu144", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2014-07", "series_number": "1", "volume": "198", "issue": "1", "pages": "385-413" }, { "id": "authors:dvp65-7bj75", "collection": "authors", "collection_id": "dvp65-7bj75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140829-084652794", "type": "article", "title": "Modeling deformation induced by seasonal variations of continental water in the Himalaya region: Sensitivity to Earth elastic structure", "author": [ { "family_name": "Chanard", "given_name": "K.", "orcid": "0000-0001-9934-9621", "clpid": "Chanard-K" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ramillien", "given_name": "G.", "clpid": "Ramillien-G" }, { "family_name": "Genrich", "given_name": "J.", "clpid": "Genrich-J-F" } ], "abstract": "Strong seasonal variations of horizontal and vertical positions are observed on GPS time series from stations located in Nepal, India, and Tibet (China). We show that this geodetic deformation can be explained by seasonal variations of continental water storage driven by the monsoon. For this purpose, we use satellite data from the Gravity Recovery and Climate Experiment to determine the time evolution of surface loading. We compute the expected geodetic deformation assuming a perfectly elastic Earth model. We consider Green's functions, describing the surface deformation response to a point load, for an elastic homogeneous half-space model and for a layered nonrotating spherical Earth model based on the Preliminary Reference Earth Model and a local seismic velocity model. The amplitude and phase of the seasonal variation of the vertical and horizontal geodetic positions can be jointly adjusted only with the layered Earth model, while an elastic half-space model fails, emphasizing the importance of using a realistic Earth elastic structure to model surface displacements induced by surface loading. We demonstrate, based on a formal inversion, that the fit to the geodetic data can be improved by adjusting the layered Earth model. Therefore, the study also shows that the modeling of geodetic seasonal variations provides a way to probe the elastic structure of the Earth, even in the absence of direct measurements of surface load variations.", "doi": "10.1002/2013JB010451", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2014-06", "series_number": "6", "volume": "119", "issue": "6", "pages": "5097-5113" }, { "id": "authors:m7aft-v3574", "collection": "authors", "collection_id": "m7aft-v3574", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140828-130315677", "type": "article", "title": "Spatiotemporal evolution of seismic and aseismic slip on the Longitudinal Valley Fault, Taiwan", "author": [ { "family_name": "Thomas", "given_name": "Marion Y.", "orcid": "0000-0002-4335-8841", "clpid": "Thomas-M-Y" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Champenois", "given_name": "Johann", "clpid": "Champenois-J" }, { "family_name": "Lee", "given_name": "Jian-Cheng", "clpid": "Lee-Jian-Cheng" }, { "family_name": "Kuo", "given_name": "Long-Chen", "clpid": "Kuo-Long-Chen" } ], "abstract": "The Longitudinal Valley Fault (LVF) in eastern Taiwan is a high slip rate fault (about 5 cm/yr), which exhibits both seismic and aseismic slip. Deformation of anthropogenic features shows that aseismic creep accounts for a significant fraction of fault slip near the surface, whereas a fraction of the slip is also seismic, since this fault has produced large earthquakes with five M_w>6.8 events in 1951 and 2003. In this study, we analyze a dense set of geodetic and seismological data around the LVF, including campaign mode Global Positioning System(GPS) measurements, time series of daily solutions for continuous GPS stations (cGPS), leveling data, and accelerometric records of the 2003 Chenkung earthquake. To enhance the spatial resolution provided by these data, we complement them with interferometric synthetic aperture radar (InSAR) measurements produced from a series of Advanced Land Observing Satellite images processed using a persistent scatterer technique. The combined data set covers the entire LVF and spans the period from 1992 to 2010. We invert this data to infer the temporal evolution of fault slip at depth using the Principal Component Analysis-based Inversion Method. This technique allows the joint inversion of diverse data, taking the advantage of the spatial resolution given by the InSAR measurements and the temporal resolution afforded by the cGPS data. We find that (1) seismic slip during the 2003 Chengkung earthquake occurred on a fault patch which had remained partially locked in the interseismic period, (2) the seismic rupture propagated partially into a zone of shallow aseismic interseismic creep but failed to reach the surface, and (3) that aseismic afterslip occurred around the area that ruptured seismically. We find consistency between geodetic and seismological constraints on the partitioning between seismic and aseismic creep. About 80\u201390% of slip on the southern section of LVF in the 0\u201326 km, seismogenic depth range, is actually aseismic. We infer that the clay-rich Lichi M\u00e9lange is the key factor promoting aseismic creep at shallow depth.", "doi": "10.1002/2013JB010603", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2014-06", "series_number": "6", "volume": "119", "issue": "6", "pages": "5114-5139" }, { "id": "authors:0m3g3-knq25", "collection": "authors", "collection_id": "0m3g3-knq25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140724-154902013", "type": "article", "title": "The seismic cycle in the area of the 2011 M_w9.0 Tohoku-Oki earthquake", "author": [ { "family_name": "Perfettini", "given_name": "H.", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We model seismic and aseismic slip on the Japan megathrust in the area of the M_w9.0, 2011 Tohoku-Oki earthquake based on daily time series from 400 GPS stations of the GEONET network and campaign measurements of six sea floor displacements. The coseismic and postseismic slip distributions are inverted simultaneously using principal component analysis-based inversion method (PCAIM). Exploring a wide range of boundary conditions and regularization constraints, we found the coseismic slip distribution to be quite compact with a peak slip between 30 and 50 m near the trench. Our model shows deep afterslip fringing the downdip edge of the coseismic rupture but also a dominant zone of shallow afterslip. Afterslip over the first 279 days following the main shock represents about 40% of the coseismic moment. We compare the coseismic and postseismic models with an interseismic coupling model derived from inland and sea bottom measurements determined in a self-consistent manner. Assuming that seismic and aseismic slip had to match the long-term slip rate along the megathrust, the recurrence time of M_w9.0 earthquakes is estimated to 100\u2013300 years, while historical and paleotsunami records suggest a return period more of the order of 1000 years. The discrepancy is smaller if the shallower portion of the megathrust is assumed to produce both aseismic slip, as the afterslip model suggests, and seismic slip during occasional large tsunamigenic earthquakes.", "doi": "10.1002/2013JB010697", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2014-05", "series_number": "5", "volume": "119", "issue": "5", "pages": "4469-4515" }, { "id": "authors:vns81-2s029", "collection": "authors", "collection_id": "vns81-2s029", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140509-070750779", "type": "article", "title": "The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Wei", "given_name": "Shengji", "clpid": "Wei-Shengji" }, { "family_name": "Ampuero", "given_name": "Jean-Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Meng", "given_name": "Lingsen", "orcid": "0000-0003-2428-0548", "clpid": "Meng-Lingsen" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Jolivet", "given_name": "Romain", "orcid": "0000-0002-9896-3651", "clpid": "Jolivet-R" }, { "family_name": "Duputel", "given_name": "Zacharie", "clpid": "Duputel-Z" }, { "family_name": "Helmberger", "given_name": "Don", "clpid": "Helmberger-D-V" } ], "abstract": "We analyse the Mw 7.7 Balochistan earthquake of 09/24/2013 based on ground surface deformation measured from sub-pixel correlation of Landsat-8 images, combined with back-projection and finite source modeling of teleseismic waveforms. The earthquake nucleated south of the Chaman strike-slip fault and propagated southwestward along the Hoshab fault at the front of the Kech Band. The rupture was mostly unilateral, propagated at 3 km/s on average and produced a 200 km surface fault trace with purely strike-slip displacement peaking to 10 m and averaging around 6 m. The finite source model shows that slip was maximum near the surface. Although the Hoshab fault is dipping by 45\u00b0 to the North, in accordance with its origin as a thrust fault within the Makran accretionary prism, slip was nearly purely strike-slip during that earthquake. Large seismic slip on such a non-optimally oriented fault was enhanced possibly due to the influence of the free surface on dynamic stresses or to particular properties of the fault zone allowing for strong dynamic weakening. Strike-slip faulting on thrust fault within the eastern Makran is interpreted as due to eastward extrusion of the accretionary prism as it bulges out over the Indian plate. Portions of the Makran megathrust, some thrust faults in the Kirthar range and strike-slip faults within the Chaman fault system have been brought closer to failure by this earthquake. Aftershocks cluster within the Chaman fault system north of the epicenter, opposite to the direction of rupture propagation. By contrast, few aftershocks were detected in the area of maximum moment release. In this example, aftershocks cannot be used to infer earthquake characteristics.", "doi": "10.1016/j.epsl.2014.01.036", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2014-04-01", "volume": "391", "pages": "128-134" }, { "id": "authors:tc3en-62n23", "collection": "authors", "collection_id": "tc3en-62n23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140703-104019674", "type": "article", "title": "Quasi-dynamic versus fully dynamic simulations of earthquakes and aseismic slip with and without enhanced coseismic weakening", "author": [ { "family_name": "Thomas", "given_name": "Marion Y.", "orcid": "0000-0002-4335-8841", "clpid": "Thomas-M-Y" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Noda", "given_name": "Hiroyuki", "clpid": "Noda-Hiroyuki" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Physics-based numerical simulations of earthquakes and slow slip, coupled with field observations and laboratory experiments, can, in principle, be used to determine fault properties and potential fault behaviors. Because of the computational cost of simulating inertial wave-mediated effects, their representation is often simplified. The quasi-dynamic (QD) approach approximately accounts for inertial effects through a radiation damping term. We compare QD and fully dynamic (FD) simulations by exploring the long-term behavior of rate-and-state fault models with and without additional weakening during seismic slip. The models incorporate a velocity-strengthening (VS) patch in a velocity-weakening (VW) zone, to consider rupture interaction with a slip-inhibiting heterogeneity. Without additional weakening, the QD and FD approaches generate qualitatively similar slip patterns with quantitative differences, such as slower slip velocities and rupture speeds during earthquakes and more propensity for rupture arrest at the VS patch in the QD cases. Simulations with additional coseismic weakening produce qualitatively different patterns of earthquakes, with near-periodic pulse-like events in the FD simulations and much larger crack-like events accompanied by smaller events in the QD simulations. This is because the FD simulations with additional weakening allow earthquake rupture to propagate at a much lower level of prestress than the QD simulations. The resulting much larger ruptures in the QD simulations are more likely to propagate through the VS patch, unlike for the cases with no additional weakening. Overall, the QD approach should be used with caution, as the QD simulation results could drastically differ from the true response of the physical model considered.", "doi": "10.1002/2013JB010615", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2014-03", "series_number": "3", "volume": "119", "issue": "3", "pages": "1986-2004" }, { "id": "authors:9ka0c-c3h43", "collection": "authors", "collection_id": "9ka0c-c3h43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140428-143524749", "type": "article", "title": "Coseismic thrusting and folding in the 1999 M_w 7.6 Chi-Chi earthquake: A high-resolution approach by aerial photos taken\n from Tsaotun, central Taiwan", "author": [ { "family_name": "Kuo", "given_name": "Yu-Ting", "clpid": "Kuo-Yu-Ting" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Shyu", "given_name": "J. Bruce H.", "orcid": "0000-0002-2564-3702", "clpid": "Shyu-J-Bruce-H" }, { "family_name": "Lai", "given_name": "Kuang-Yin", "clpid": "Lai-Kuang-Yin" }, { "family_name": "Kuo", "given_name": "Yu-Ju", "clpid": "Kuo-Yu-Ju" } ], "abstract": "We used aerial photos taken before and after the 21 September 1999, M_w 7.6, Chi-Chi earthquake in central Taiwan to measure the near-field ground deformation. A total of 12 pairs of images were processed with Co-registration of Optically Sensed Images and Correlation to produce a horizontal displacement map of a 10 km \u00d7 10 km area near Tsaotun. Using pairs of images with different viewing angles, both the horizontal and vertical slip across the fault zone can be measured. Our measurements when resampled into lower resolution are consistent with lower resolution measurements of horizontal displacements obtained from SPOT images, as well as with vertical displacements obtained from repeated leveling measurements and field observations. Horizontal strain is strongly localized along the Chelungpu fault (CLPF) and along a secondary scarp that runs parallel to the CLPF about 2 km to the east, the Ailiao fold scarp (ALF). This pattern closely matches the surface ruptures mapped in the field. Horizontal strain across CLPF correlates remarkably well with the topographic features produced by long-term deformation. The cumulative horizontal shortening across the CLPF and ALF amounts to 4.9\u2009\u00b1\u20090.4 and 6.1\u2009\u00b1\u20090.6 m, respectively, and fault-parallel displacement is 3.4\u2009\u00b1\u20090.4 m. The pattern of surface strain is consistent with the interpretation of the ALF as a fold scarp formed over an active axial hinge zone. This study shows that, even in this compressional setting, most surface deformation is localized within narrow fault zones or active axial hinges.", "doi": "10.1002/2013JB010308", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2014-01-23", "series_number": "1", "volume": "119", "issue": "1", "pages": "645-660" }, { "id": "authors:qg77m-k8e67", "collection": "authors", "collection_id": "qg77m-k8e67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131219-075504407", "type": "article", "title": "Late Pleistocene glacial advances in the western Tibet interior", "author": [ { "family_name": "Amidon", "given_name": "William H.", "clpid": "Amidon-W-H" }, { "family_name": "Bookhagen", "given_name": "Bodo", "clpid": "Bookhagen-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Smith", "given_name": "Taylor", "clpid": "Smith-T" }, { "family_name": "Rood", "given_name": "Dylan", "clpid": "Rood-D-H" } ], "abstract": "It has long been observed that the timing of glacial advances is asynchronous across the Himalaya\u2013Karakoram\u2013Tibet Plateau (HKTP) but the climatic implications, if any, remain unclear. Resolving this question requires additional glacial chronologies from unique spatial and climatic regimes as well as an analysis of how glaciers within different regimes are likely to have responded to past climate changes. This study presents a ^(10)Be\u2013^(21)Ne chronology from the Mawang Kangri range of western Tibet (\u223c34\u00b0N, 80\u00b0E); an arid high-elevation site. We identify advances at \u223c123, 83, and 56 kyr, which agree reasonably well with sites in the immediate vicinity, but are asynchronous relative to sites across the entire HKTP, and relative to sites in the western HKTP. To evaluate HKTP-wide asynchroneity, we compile dated glacial chronologies and classify them by the approximate timing of their maximum recent advance. This result shows a strong spatial clustering of young (MIS 1\u20132) relative to older (MIS 3\u20135) maximum advances. Further comparison with modern precipitation, temperature, and topographic data show that the pattern of HKTP-wide asynchroneity is broadly independent of topography and can potentially be explained by local responses to changes in temperature at either very warm-wet or cold-dry sites. Sites that receive intermediate amounts of precipitation are more ambiguous, although spatial clustering of MIS 1\u20132 vs. MIS 3\u20135 advances is suggestive of past variations in precipitation at these sites. In western Tibet, no spatial or climatic correlation is observed with the timing of maximum glacial advances. We suggest this could arise from mis-interpretation of disparate boulder ages generated by a prolonged MIS-3/4 glacial advance in the western HKTP.", "doi": "10.1016/j.epsl.2013.08.041", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2013-11-01", "volume": "381", "pages": "210-221" }, { "id": "authors:d5wm9-hg886", "collection": "authors", "collection_id": "d5wm9-hg886", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131220-080054379", "type": "article", "title": "Megathrust friction determined from mechanical analysis of the forearc in the Maule earthquake area", "author": [ { "family_name": "Cubas", "given_name": "Nadaya", "clpid": "Cubas-N" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Souloumiac", "given_name": "Pauline", "clpid": "Souloumiac-P" }, { "family_name": "Leroy", "given_name": "Yves", "clpid": "Leroy-Y" } ], "abstract": "The seismogenic potential of a given fault depends essentially on its frictional properties and on the mechanical properties of the medium. Determining the spatio-temporal variations of frictional properties is therefore a key issue in seismotectonics. This study aims to characterize the friction on the South America megathrust in the 2010 Mw 8.8 Maule earthquake area from mechanical analysis of the forearc structure and morphology. Based on the critical taper theory, we first show that the rupture area of the Maule earthquake, also shown to be locked in the interseismic period, coincides with the stable part of the wedge. In the surrounding area, the wedge is critical, a finding consistent with various evidence for active deformation there. This is in particular true for the Arauco Peninsula area which seems to have arrested the Maule earthquake\u02bcs rupture to the South. This observation lends support to the view that the seismic rupture is inhibited when propagating beneath a critical area. The geometry of the critical portion of the wedge suggests a standard internal friction (\u03bc_(int)=0.7\u00b10.13) and a hydrostatic pore pressure within the wedge. The effective friction beneath the critical outer wedge is estimated to be \u00b5^(eff)_b = 0.7 \u00b1 0.13. This could be related to intrinsically low friction minerals (clay) or high pore pressure along the megathrust. We next use the limit analysis approach to constrain the variation of the effective friction along the megathrust based on the location and geometry of internal faulting within the forearc. A low effective friction is found within the rupture area (\u00b5^(eff)_b \u2264 0.14) to explain the reactivation of thrust fault such as the Santa Maria, updip of the coseismic rupture, or the activation of normal splay faults downdip of the rupture area. The low effective friction found there could reflect strong dynamic weakening.", "doi": "10.1016/j.epsl.2013.07.037", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2013-11-01", "volume": "381", "pages": "92-103" }, { "id": "authors:qevbf-c0w60", "collection": "authors", "collection_id": "qevbf-c0w60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131101-103258519", "type": "article", "title": "Kinematic Inversion of Physically Plausible Earthquake Source Models Obtained from Dynamic Rupture Simulations", "author": [ { "family_name": "Konca", "given_name": "Ali Ozgun", "clpid": "Konca-A-G" }, { "family_name": "Kaneko", "given_name": "Yoshihiro", "orcid": "0000-0003-2342-0131", "clpid": "Kaneko-Yoshihiro" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "One approach to investigate earthquake source processes is to produce kinematic source models from inversion of seismic records and geodetic data. The setup of the inversion requires a variety of assumptions and constraints to restrict the range of possible models. Here, we evaluate to what extent physically plausible earthquake scenarios are reliably restituted in spite of these restrictions. We study which characteristics of ruptures, such as rupture velocity, slip distribution, stress drop, rise time, and slip function, can be reliably determined from the inversion of near\u2010field seismic and geodetic data. Using spontaneous dynamic rupture simulations, we generate five earthquake scenarios, each of which has different characteristics of the source process. Then we conduct a blind test by modeling the synthetic near\u2010source data using a standard inversion scheme that optimizes the fit to the observations while searching for solutions with minimum roughness. The inversion procedure assumes a rupture front propagating away from the hypocenter with variable rupture velocity and a simple cosine slip\u2010time function. Our results show that, overall, slip distribution and stress drop are reasonably well determined even for input models with relatively complex histories (such as a subshear rupture transitioning to supershear speeds). Depth\u2010averaged rupture velocities are also reasonably well resolved although their estimate progressively deteriorates away from the hypocenter. The local rise time and slip function are not well resolved, but there is some sensitivity to the rupture pulse width, which can be used to differentiate between pulse\u2010like and crack\u2010like ruptures. Our test for understanding the inaccuracies in Green's functions shows that random 3D perturbations of 5% standard deviation do not lead to significant degradation of the estimation of earthquake source parameters. As remedies to the current limitations, we propose smoothing slip function parameters and using more complicated inversion schemes only if data necessitates them.", "doi": "10.1785/0120120358", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2013-10", "series_number": "5", "volume": "103", "issue": "5", "pages": "2621-2644" }, { "id": "authors:gxspt-0cm29", "collection": "authors", "collection_id": "gxspt-0cm29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131101-080433258", "type": "article", "title": "Detecting periodicities and declustering in earthquake catalogs using the Schuster spectrum, application to Himalayan seismicity", "author": [ { "family_name": "Ader", "given_name": "Thomas J.", "clpid": "Ader-T-J" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We show that the Schuster test alone does not provide a sufficient condition to assert the existence of a periodicity in an earthquake catalog. Such periodicities can be detected by computing a spectrum of Schuster p-values (the probability to observe such a level of periodic variations in a catalog occurring out of a constant seismicity rate). We show that the detection level is slightly period dependent, and we provide an analytical expression relating the amplitude of seismicity-rate variations to the confidence level at which the probability that the observed variations be due to chance can be discarded. The Schuster spectrum also provides information about the deviation from a sinusoidal function of the periodicity of the seismicity rate, and identifies an eventual imperfect declustering of the catalog, making it coincidently a potential tool to determine whether or not a catalog has been properly declustered. Applying this tool to the Nepalese seismicity, we demonstrate annual variations of the seismicity rate of amplitude up to 40%, while no other periodicity appears. In particular, no variations of seismicity at any of the tidal periods are observed, indicating that the relative amplitude response of the seismicity at these periods is less than 18%.", "doi": "10.1016/j.eps1.2013.06.032", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2013-09", "volume": "377", "pages": "97-105" }, { "id": "authors:arcb4-dvy47", "collection": "authors", "collection_id": "arcb4-dvy47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-094955566", "type": "article", "title": "Low friction along the high slip patch of the 2011 Mw 9.0 Tohoku-Oki earthquake required from the wedge structure and extensional splay faults", "author": [ { "family_name": "Cubas", "given_name": "N.", "clpid": "Cubas-N" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Leroy", "given_name": "Y. M.", "clpid": "Leroy-Y-M" }, { "family_name": "Pons", "given_name": "A.", "clpid": "Pons-A" } ], "abstract": "We analyze the mechanical properties needed to\naccount for the large shallow slip during the 2011\nTohoku-Oki earthquake and the activation of landward\nnormal faulting within the forearc. We show that the\nmorphology and internal structure of the forearc follows\nclosely the prediction of the critical Coulomb wedge in\nhorizontal compression, implying a high internal pore\npressure ratio (\u03bb = 0.7 + 0.14/ \u2013 0.48) and a low effective\nbasal friction (\u03bc^(eff)_b = 0.14 + 0.18/ \u2013 0.04). We then show that the activation of the normal fault requires a lower effective basal friction beneath the outer wedge than beneath the inner wedge (\u03bc_outer \u2264 0.015), possibly due to transient dynamic weakening associated to the seismic rupture. Forearc normal faults could be considered as evidence for very efficient dynamic weakening along the megathrust and typify megathrust with high tsunamigenic potential.", "doi": "10.1002/grl.50682", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2013-08-28", "series_number": "16", "volume": "40", "issue": "16", "pages": "4231-4237" }, { "id": "authors:kt1ft-s9585", "collection": "authors", "collection_id": "kt1ft-s9585", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131108-111334162", "type": "article", "title": "Landslide velocity, thickness, and rheology from remote sensing: La Clapiere landslide, France", "author": [ { "family_name": "Booth", "given_name": "Adam M.", "orcid": "0000-0002-7339-0594", "clpid": "Booth-A-M" }, { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Delacourt", "given_name": "Christophe", "clpid": "Delacourt-C" } ], "abstract": "Quantifying the velocity, volume, and rheology of deep, slow-moving landslides is essential for hazard prediction and understanding landscape evolution, but existing field-based methods are difficult or impossible to implement at remote sites. Here we present a novel and widely applicable method for constraining landslide 3-D deformation and thickness by inverting surface change data from repeat stereo imagery. Our analysis of La Clapi\u00e8re, an ~1 km^2 bedrock landslide, reveals a concave-up failure surface with considerable roughness over length scales of tens of meters. Calibrating the thickness model with independent, local thickness measurements, we find a maximum thickness of 163 m and a rheology consistent with distributed deformation of the highly fractured landslide material, rather than sliding of an intact, rigid block. The technique is generally applicable to any mass movements that can be monitored by active or historic remote sensing.", "doi": "10.1002/grl.50828", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2013-08-28", "series_number": "16", "volume": "40", "issue": "16", "pages": "4299-4304" }, { "id": "authors:1yprd-j1371", "collection": "authors", "collection_id": "1yprd-j1371", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130923-105214527", "type": "article", "title": "Shear heating not a cause of inverted metamorphism", "author": [ { "family_name": "Kidder", "given_name": "Steven B.", "clpid": "Kidder-S-B" }, { "family_name": "Herman", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Herman-F" }, { "family_name": "Saleeby", "given_name": "Jason", "clpid": "Saleeby-J-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ducea", "given_name": "Mihai N.", "orcid": "0000-0002-5322-0782", "clpid": "Ducea-M-N" }, { "family_name": "Chapman", "given_name": "Alan D.", "orcid": "0000-0001-9865-603X", "clpid": "Chapman-A-D" } ], "abstract": "An archetypal example of inverted metamorphism purportedly resulting from shear heating\nis found in the Pelona Schist of southern California (United States). Recent studies demonstrate\nthat the Pelona Schist was subducted and accreted at the onset of Laramide fl at\nsubduction under thermal and kinematic conditions not considered in earlier numerical models.\nTo test the shear heating hypothesis under these conditions, we constructed a thermokinematic\nmodel of flat subduction initiation involving continuous accretion of the schist. A\nneighborhood algorithm inversion demonstrates that available metamorphic and thermochronologic\nconstraints in the Sierra Pelona mountains are satisfied only if accretion rates\nwere 0.2\u20133.6 km/m.y and shear heating was minimal (shear stress 0\u201319 MPa). Minimal shear\nheating is also consistent with an inversion of models constrained by thermochronology of\nthe East Fork (of the San Gabriel River) exposure of the schist. Shear heating inhibits the\nformation of modeled inverted gradients during accretion and should not be considered an\nimportant factor in their generation.", "doi": "10.1130/G34289.1", "issn": "0091-7613", "publisher": "Geological Society of America", "publication": "Geology", "publication_date": "2013-08", "series_number": "8", "volume": "41", "issue": "8", "pages": "899-902" }, { "id": "authors:mg003-rn416", "collection": "authors", "collection_id": "mg003-rn416", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130816-155608675", "type": "article", "title": "Kinematic fault slip evolution source models of the 2008 M7.9 Wenchuan earthquake in China from SAR interferometry, GPS and teleseismic analysis and implications for Longmen Shan tectonics", "author": [ { "family_name": "Fielding", "given_name": "Eric J.", "orcid": "0000-0002-6648-8067", "clpid": "Fielding-E-J" }, { "family_name": "Sladen", "given_name": "Anthony", "orcid": "0000-0003-4126-0020", "clpid": "Sladen-A" }, { "family_name": "Li", "given_name": "Zhenhong", "clpid": "Li-Zhenhong" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "B\u00fcrgmann", "given_name": "Roland", "orcid": "0000-0002-3560-044X", "clpid": "B\u00fcrgmann-R" }, { "family_name": "Ryder", "given_name": "Isabelle", "clpid": "Ryder-I-M-A" } ], "abstract": "The M_w 7.9 2008 Wenchuan earthquake ruptured about 280\u2009km of faults in the Longmen Shan of Sichuan province, China, at the eastern edge of the Tibetan Plateau. We use teleseismic waveforms with geodetic data from Global Positioning System, synthetic aperture radar interferometry and image amplitude correlation to produce a source model of this earthquake. The model describes evolution of fault slip during the earthquake. The geodetic data constrains the spatial distribution of fault slip and the seismic waveforms constrain mostly the time evolution of slip. We find that the earthquake started with largely thrust motion on an imbricate system of faults beneath the central Longmen Shan, including the Beichuan Fault and Pengguan Fault, with fault slip at depth extending up to 50\u2009km northwest of the mountain front. The fault ruptures continued northeast along the Beichuan Fault with more oblique slip (right-lateral and thrust) and the proportion of lateral motion increasing in the northern Longmen Shan. The northernmost fault segment has a much steeper dip, consistent with nearly pure strike-slip motion. The kinematic source model shows that the rupture propagated to the northeast at about 2.5\u20133.0\u2009km\u2009s^(\u22121), producing a cascade of subevents with a total duration of about 110 s. The complex fault ruptures caused shortening and uplift of the extremely steep central Longmen Shan, which supports models where the steep edge of the plateau is formed by thrusting over the strong crust of the Sichuan Basin.", "doi": "10.1093/gji/ggt155", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2013-08", "series_number": "2", "volume": "194", "issue": "2", "pages": "1138-1166" }, { "id": "authors:k154t-htp67", "collection": "authors", "collection_id": "k154t-htp67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131104-085648056", "type": "article", "title": "New constraints on dike injection and fault slip during the 1975\u20131984 Krafla rift crisis, NE Iceland", "author": [ { "family_name": "Hollingsworth", "given_name": "J.", "orcid": "0000-0003-0122-296X", "clpid": "Hollingsworth-J" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Correlation of KH9 spy and SPOT5 satellite images, airphotos, digital elevation model differencing, electronic distance measurement, and leveling survey data is used to constrain the deformation resulting from the 1975\u20131984 Krafla rifting crisis. We find that diking typically extends to depths of 5\u2009km, while the dike tops range from 0\u2009km in the caldera region to 3\u2009km at the northern end of the rift. Extension is accommodated by diking at depth and normal faulting in the shallowest crust. In the southern section of the Krafla rift, surface opening is 80% of the dike opening at depth. Over the 70\u201380\u2009km length of the rift, the average dike opening was 4.3\u20135.4\u2009m. From these estimates, we calculate the total geodetic moment released over the Krafla rift crisis, 4.4\u20139.0\u00d710^(19)\u2009Nm, which is an order of magnitude higher than the seismic moment released over the same time period, ~5.8\u00d710^(18)\u2009Nm. The total volume of magma added to the upper crust was 1.1\u20132.1\u00d710^9m^3. This study highlights how optical image correlation using inexpensive declassified spy satellite and airphotos, combined with simple models of crustal deformation, can provide important constraints on the deformation resulting from past earthquake and volcanic events.", "doi": "10.1002/jgrb.50223", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2013-07-11", "series_number": "7", "volume": "118", "issue": "7", "pages": "3707-3727" }, { "id": "authors:nk375-6bf06", "collection": "authors", "collection_id": "nk375-6bf06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131104-094125115", "type": "article", "title": "Spatially variable fault friction derived from dynamic modeling of aseismic afterslip due to the 2004 Parkfield earthquake", "author": [ { "family_name": "Chang", "given_name": "Shu-Hao", "clpid": "Chang-Shu-Hao" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-S" }, { "family_name": "Lee", "given_name": "Jian-Cheng", "clpid": "Lee-Jian-Cheng" } ], "abstract": "We investigate fault friction from dynamic modeling of fault slip prior to and following the M_w 6.0 earthquake which ruptured the Parkfield segment of the San Andreas Fault in 2004. The dynamic modeling assumes a purely rate-strengthening friction law, with a logarithmic dependency on sliding rate: \u03bc= \u03bc*+(a-b)ln(v/v*). The initial state of stress is explicitly taken into account, and afterslip is triggered by the stress change induced by the earthquake source model given a priori. We consider different initial stress states and two coseismic models, and invert for the other model parameters using a nonlinear inversion scheme. The model parameters include the reference friction \u03bc*, the friction rate dependency characterized by the quantity a-b, assumed to be either uniform or depth dependent. The model parameters are determined from fitting the transient postseismic geodetic signal measured at continuous GPS stations. Our study provides a view of frictional properties at the kilometers scale over the 0\u201315\u2009km depth illuminated by the coseismic stress change induced by the Parkfield earthquake. The reference friction is estimated to be between 0.1 and 0.5. With independent a priori constraints on the amplitude of differential stress, the range of possible values narrows down to 0.1\u20130.17. The friction rate coefficient a-b is estimated to be \u223c\u200910^(\u2212\u20093)\u2009\u2212\u200910^(\u2212\u20092) with a hint that it increases upward from about 1\u20133\u2009\u00d7\u200910^(\u20133) at 3\u20137\u2009km depth to about 4\u20137\u2009\u00d7\u200910^(\u20133) at 0\u20131\u2009km depth. It is remarkable that our results are consistent with frictional properties measured on rock samples recovered from the fault zone thanks to the San Andreas Fault Observatory at Depth experiment.", "doi": "10.1002/jgrb.50231", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2013-07-02", "series_number": "7", "volume": "118", "issue": "7", "pages": "3431-3447" }, { "id": "authors:fag14-b6q89", "collection": "authors", "collection_id": "fag14-b6q89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131104-111155904", "type": "article", "title": "Modeling the 2012 Wharton basin earthquakes off-Sumatra: Complete lithospheric failure", "author": [ { "family_name": "Wei", "given_name": "Shengji", "clpid": "Wei-Shengji" }, { "family_name": "Helmberger", "given_name": "Don", "clpid": "Helmberger-D-V" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "A sequence of large strike-slip earthquakes occurred west of Sunda Trench beneath the Wharton Basin. First reports indicate that the main shock was extremely complex, involving three to four subevents (M_w\u2009>\u20098) with a maze of aftershocks. We investigate slip models of the two largest earthquakes by joint inversion of regional and teleseismic waveform data. Using the M_w 7.2 foreshock, we developed hybrid Green's Functions for the regional stations to approximate the mixture of oceanic and continental paths. The main shock fault geometry is defined based on the back projection results, point-source mechanisms, aftershock distribution, and fine tune of grid searches. The fault system contains three faults, labeled F1 (89\u00b0/289\u00b0 for dip/strike), F2 (74\u00b0/20\u00b0), and F3 (60\u00b0/310\u00b0). The inversion indicates that the main rupture consisted of a cascade of high-stress drop asperities (up to 30\u2009MPa), extending as deep as 50\u2009km. The rupture propagated smoothly from one fault to the next (F1, F2, and F3 in sequence) with rupture velocities of 2.0\u20132.5\u2009km/s. The whole process lasted about 200\u2009s, and the major moment release (>70%) took place on the N-S oriented F2. The M_w 8.2 aftershock happened about 2\u2009h later on a N-S oriented fault with a relatively short duration (~60\u2009s) and also ruptured as deep as 50\u2009km. The slip distributions suggest that the earthquake sequence was part of a broad left-lateral shear zone between the Australian and Indian plates and ruptured the whole lithosphere. These earthquakes apparently reactivated existing fracture zones and were probably triggered by unclamping of the great Sumatran earthquake of 2004.", "doi": "10.1002/jgrb.50267", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2013-07", "series_number": "7", "volume": "118", "issue": "7", "pages": "3592-3609" }, { "id": "authors:e49gd-fkz68", "collection": "authors", "collection_id": "e49gd-fkz68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130523-092356435", "type": "article", "title": "Application of titanium-in-quartz thermobarometry to greenschist facies veins and recrystallized quartzites in the Hs\u00fcehshan range, Taiwan", "author": [ { "family_name": "Kidder", "given_name": "S.", "clpid": "Kidder-S-B" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chan", "given_name": "Y.-C.", "clpid": "Chan-Yu-Chang" } ], "abstract": "The accuracy, reliability and best practises of Ti-in-quartz thermobarometry (TitaniQ) in greenschist facies rocks have not been established. To address these issues, we measured Ti concentrations in rutile-bearing samples of moderately deformed, partially recrystallized quartzite and vein quartz from the Hs\u00fcehshan range, Taiwan. The spread of Ti concentrations of recrystallized grains in quartzite correlates with recrystallized grain size. Recrystallized quartz (grain size ~100\u2013200 \u03bcm) that formed during early deformation within the biotite stability field shows a marked increase in intermediate Ti-concentration grains (~1\u201310 ppm) relative to detrital porphyroclasts (Ti ~0.1\u2013200 ppm). Fine recrystallized quartz (~5% of the samples by area, grain size ~10\u201320 \u03bcm) has a further restricted Ti concentration peaking at 0.8\u20132 ppm. This trend suggests equilibration of Ti in recrystallized quartz with a matrix phase during deformation and cooling. Unlike previously documented examples, Ti concentration in the quartzite is inversely correlated with blue cathodoluminescence. Deformation was associated with a minimum grain boundary diffusivity of Ti on the order of 10^(\u221222)m^2 s^(\u22121). Vein emplacement and quartzite recrystallization are independently shown to have occurred at 250\u2013350 \u00b0C and 300\u2013410 \u00b0C, respectively, with lithostatic pressure of 3\u20134 kbar (assuming a geothermal gradient of 25\u00b0 km^(\u22121)), and with hydrostatic fluid pressure. Estimates of the accuracy of TitaniQ at these conditions depend on whether lithostatic or fluid pressure is used in the TitaniQ calibration. Using lithostatic pressure and these temperatures, the Thomas et al. (2010) calibration yields Ti concentrations within error of concentrations measured by SIMS. If fluid pressure is instead used, predicted temperatures are ~30\u201340 \u00b0C too low. TitaniQ has potential to yield accurate PT information for vein emplacement and dynamic recrystallization of quartz at temperatures as low as ~250 \u00b0C, however clarification of the relevant pressure term and further tests in rutile-present rocks are warranted.", "doi": "10.5194/se-4-1-2013", "issn": "1869-9510", "publisher": "European Geosciences Union", "publication": "Solid Earth", "publication_date": "2013-01-07", "series_number": "1", "volume": "4", "issue": "1", "pages": "1-21" }, { "id": "authors:jwegq-85b59", "collection": "authors", "collection_id": "jwegq-85b59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160318-162707037", "type": "article", "title": "A Geostationary Optical Seismometer, Proof of Concept", "author": [ { "family_name": "Michel", "given_name": "R.", "clpid": "Michel-R" }, { "family_name": "Ampuero", "given_name": "J.-P.", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Leprince", "given_name": "S.", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Redding", "given_name": "D. C.", "clpid": "Redding-D-C" }, { "family_name": "Somala", "given_name": "S. N.", "clpid": "Somala-S-N" } ], "abstract": "We discuss the possibility of imaging the propagation\nof seismic waves from a very large space-based optical telescope.\nImages of seismic waves propagating at the Earth's surface would\nbe an invaluable source of information for investigating earthquake\nphysics and the effect of the subsurface on earthquake\nground motions. This application would require ground displacement\nmeasurements at about every 100 m, with centimetric accuracy,\nand temporal sampling on the order of 1 Hz. A large field\nof view (> 10^5 km^2) is required to measure the full extent of a\nlarge earthquake in the areas of interest. A geostationary optical\ntelescope with a large aperture appears to be the most promising\nsystem. We establish preliminary technical requirements for such\na system, which lead us to consider a telescope with an angular\nfield of view of 0.8\u00b0 and with an aperture greater than 4 m.\nWe discuss and quantify the various sources of noise that would\nlimit such a system: atmospheric turbulence, evolution of ground\nreflectance and solar incidence angle, and stability of the platform\nat 1 Hz. We present numerical simulations, which account for\nthese sources of noise. They show that key details of the seismic\nwave field, hardly detectable using ground-based instruments,\nwould indeed be imaged by such a system. At the upper limit of\nmodern technology, data flow would be about 20\u201350 Gb \u00b7 s^(\u22121), and\ndata memory would be about 50 Tb.", "doi": "10.1109/TGRS.2012.2201487", "issn": "0196-2892", "publisher": "IEEE", "publication": "IEEE Transactions on Geoscience and Remote Sensing", "publication_date": "2013-01", "series_number": "1", "volume": "51", "issue": "1", "pages": "695-703" }, { "id": "authors:49bja-4qf18", "collection": "authors", "collection_id": "49bja-4qf18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130110-142854128", "type": "article", "title": "Postseismic deformation following the 1999 Chi-Chi earthquake,\n Taiwan: Implication for lower-crust rheology", "author": [ { "family_name": "Rousset", "given_name": "Baptiste", "clpid": "Rousset-B" }, { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hsu", "given_name": "Ya-Ju", "clpid": "Hsu-Y-J" } ], "abstract": "On 1999 September 21, the Mw 7.6 Chi-Chi earthquake ruptured a segment of the\nChelungpu Fault, a frontal thrust fault of the Western Foothills of Taiwan. The stress\nperturbation induced by the rupture triggered a transient deformation across the island,\nwhich was well recorded by a wide network of continuously operating GPS stations.\nThe analysis of more than ten years of these data reveals a heterogeneous pattern of\npostseismic displacements, with relaxation times varying by a factor of more than ten,\nand large cumulative displacements at great distances, in particular along the Longitudinal\nValley in eastern Taiwan, where relaxation times are also longer. We show that while\nafterslip is the dominant relaxation process in the epicentral area, viscoelastic relaxation is\nneeded to explain the pattern and time evolution of displacements at the larger scale.\nWe model the spatiotemporal behavior of the transient deformation as the result of afterslip\non the d\u00e9collement that extends downdip of the Chelungpu thrust, and viscoelastic flow in\nthe lower crust and in the mid-crust below the Central Range. We construct a model of\ndeformation driven by coseismic stress change where afterslip and viscoelastic flow are\nfully coupled. The model is compatible with the shorter relaxation times observed in the\nnear field, which are due to continued fault slip, and the longer characteristic relaxation\ntimes and the reversed polarity of vertical displacements observed east of the Central\nRange. Our preferred model shows a viscosity of 0.5\u20131 X 10^(19) Pa s at lower-crustal depths\nand 5 X 10^(17) Pa s in the mid-crust below the Central Range, between 10 and 30 km depth.\nThe low-viscosity zone at mid-crustal depth below the Central Range coincides with a\nregion of low seismicity where rapid advection of heat due to surface erosion coupled with\nunderplating maintain high temperatures, estimated to be between 300\u00b0C and 600\u00b0C from\nthe modeling of thermo-chronology and surface heat flow data.", "doi": "10.1029/2012JB009571", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2012-12-15", "series_number": "B12", "volume": "117", "issue": "B12", "pages": "Art. No. B12405" }, { "id": "authors:hqyay-8ar02", "collection": "authors", "collection_id": "hqyay-8ar02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130110-140710735", "type": "article", "title": "Deformation during the 1975\u20131984 Krafla rifting crisis, NE Iceland, measured from historical optical imagery", "author": [ { "family_name": "Hollingsworth", "given_name": "James", "orcid": "0000-0003-0122-296X", "clpid": "Hollingsworth-J" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We measure the displacement field resulting from the 1975\u20131984 Krafla rifting crisis, NE Iceland, using optical image correlation. Images are processed using the COSI-Corr software package. Surface extension is accommodated on normal faults and fissures which bound the rift zone, in response to dike injection at depth. Correlation of declassified KH-9 spy and SPOT5 satellite images reveals extension between 1977\u20132002 (2.5 m average opening over 80 km), while correlation of aerial photos between 1957\u20131990 provide measurements of the total extension (average 4.3 m opening over 80 km). Our results show \u223c8 m of opening immediately north of Krafla caldera, decreasing to 3\u20134 m at the northern end of the rift. Correlation of aerial photos from 1957\u20131976 reveal a bi-modal pattern of opening along the rift during the early crisis, which may indicate either two different magma sources located at either end of the rift zone (a similar pattern of opening was observed in the 2005 Afar rift crisis in East Africa), or variations in rock strength along the rift. Our results provide new information on how past dike injection events accommodate long-term plate spreading, as well as providing more details on the Krafla rift crisis. This study also highlights the potential of optical image correlation using inexpensive declassified spy satellite and aerial photos to measure deformation of the Earth's surface going back many decades, thus providing a new tool for measuring Earth surface dynamics, e.g. glaciers, landsliding, coastal erosion, volcano monitoring and earthquake studies, when InSAR and GPS data are not available.", "doi": "10.1029/2012JB009140", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2012-11-14", "series_number": "B11", "volume": "117", "issue": "B11", "pages": "Art. No. B11407" }, { "id": "authors:r6pn8-vbx09", "collection": "authors", "collection_id": "r6pn8-vbx09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121214-153612362", "type": "article", "title": "Anomalously steep dips of earthquakes in the 2011 Tohoku-Oki source region and possible explanations", "author": [ { "family_name": "Zhan", "given_name": "Zhongwen", "orcid": "0000-0002-5586-2607", "clpid": "Zhan-Zhongwen" }, { "family_name": "Helmberger", "given_name": "Don", "clpid": "Helmberger-D-V" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Wu", "given_name": "Wenbo", "orcid": "0000-0002-6249-8065", "clpid": "Wu-Wenbo" }, { "family_name": "Cubas", "given_name": "Nadaya", "clpid": "Cubas-Nadaya" }, { "family_name": "Duputel", "given_name": "Zacharie", "clpid": "Duputel-Zacharie" }, { "family_name": "Chu", "given_name": "Risheng", "clpid": "Chu-Risheng" }, { "family_name": "Tsai", "given_name": "Victor C.", "orcid": "0000-0003-1809-6672", "clpid": "Tsai-V-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hudnut", "given_name": "Kenneth W.", "orcid": "0000-0002-3168-4797", "clpid": "Hudnut-K-W" }, { "family_name": "Ni", "given_name": "Sidao", "orcid": "0000-0003-2988-4850", "clpid": "Ni-Sidao" }, { "family_name": "Hetland", "given_name": "Eric", "clpid": "Hetland-E-A" }, { "family_name": "Ortega Culaciati", "given_name": "Francisco H.", "clpid": "Ortega-Culaciati-F-H" } ], "abstract": "The 2011 M_w 9.1 Tohoku-Oki earthquake had unusually large slip (over 50 m) concentrated in a relatively small region, with local stress drop inferred to be 5\u201310 times larger than that found for typical megathrust earthquakes. Here we conduct a detailed analysis of foreshocks and aftershocks (M_w 5.5\u20137.5) sampling this megathrust zone for possible clues regarding such differences in seismic excitation. We find that events occurring in the region that experienced large slip during the M_w 9.1 event had steeper dip angles (by 5\u201310\u00b0) than the surrounding plate interface. This discrepancy cannot be explained by a single smooth plate interface. We provide three possible explanations. In Model I, the oceanic plate undergoes two sharp breaks in slope, which were not imaged well in previous seismic surveys. These break-points may have acted as strong seismic barriers in previous seismic ruptures, but may have failed in and contributed to the complex rupture pattern of the Tohoku-Oki earthquake. In Model II, the discrepancy of dip angles is caused by a rough plate interface, which in turn may be the underlying cause for the overall strong coupling and concentrated energy-release. In Model III, the earthquakes with steeper dip angles did not occur on the plate interface, but on nearby steeper subfaults. Since the differences in dip angle are only 5\u201310\u00b0, this last explanation would imply that the main fault has about the same strength as the nearby subfaults, rather than much weaker. A relatively uniform fault zone with both the main fault and the subfaults inside is consistent with Model III. Higher resolution source locations and improved models of the velocity structure of the megathrust fault zone are necessary to resolve these issues.", "doi": "10.1016/j.epsl.2012.07.038", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2012-11-01", "volume": "353-35", "pages": "121-133" }, { "id": "authors:7832m-p1237", "collection": "authors", "collection_id": "7832m-p1237", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121206-101046504", "type": "article", "title": "Human-induced shaking", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "In 2011, a modest earthquake in southern Spain seriously damaged the city of Lorca. Analysis of surface deformation suggests that the quake was caused by rupture of a shallow fault patch brought closer to failure by the pumping of water from a nearby aquifer.", "doi": "10.1038/ngeo1609", "issn": "1752-0894", "publisher": "Nature Publishing Group", "publication": "Nature Geoscience", "publication_date": "2012-10-21", "series_number": "11", "volume": "5", "issue": "11", "pages": "763-764" }, { "id": "authors:m5rrr-zy256", "collection": "authors", "collection_id": "m5rrr-zy256", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121108-095123650", "type": "article", "title": "Constraints from rocks in the Taiwan orogen on crustal stress levels and rheology", "author": [ { "family_name": "Kidder", "given_name": "Steven B.", "clpid": "Kidder-S-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chan", "given_name": "Yu-Chang", "clpid": "Chan-Yu-Chang" } ], "abstract": "Taiwan's Hs\u00fcehshan range experienced penetrative coaxial deformation within and near the brittle-plastic transition between \u223c6.5 and 3 Ma. This recent and short-lasting deformation in an active, well-studied orogen makes it an ideal natural laboratory for studying crustal rheology. Recrystallized grain size piezometry in quartz and Ti-in-quartz thermobarometry yield peak differential stresses of \u223c200 MPa at 250\u2013300\u00b0C that taper off to \u223c80 MPa at \u223c350\u00b0C and \u223c14 MPa at \u223c400\u2013500\u00b0C. Stress results do not vary with lithology: recrystallized quartz veins in slates and metasiltstones yield equivalent stresses as recrystallized grains in quartzites. A minimum strain rate of 2.9 \u00d7 10^(\u221215) s^(\u22121) associated with this deformation is calculated by dividing a strain measurement (axial strain \u223c0.3) in a strongly deformed quartzite by the available 3.5 m.y. deformation interval. We estimate a maximum strain rate of 7.0 \u00d7 10^(\u221214) s^(\u22121) by distributing the geodetic convergence rate throughout a region homogeneously deformed under horizontal compression. These stress, strain rate and temperature estimates are consistent with the predictions of widely applied dislocation creep flow laws for quartzite. The samples record stress levels at the brittle-plastic transition, indicating a coefficient of friction (\u03bc) of 0.37 in the upper crust consistent with results based on critical taper. Integrated crustal strength of the Hs\u00fcehshan range amounts to 1.7 \u00d7 10^(12) N/m based on our analysis, consistent with potential energy constraints based on topography. Other strength profiles are considered, however high crustal stresses (>300 MPa) conflict with our analysis. The study supports the use of the recrystallized grain size piezometer in quartz as a quick and inexpensive method for resolving stress histories in greenschist facies rocks. For consistency with the independent constraints presented here, we find it accurate to within +20%/\u221240%, significantly better than previously recognized.", "doi": "10.1029/2012JB009303", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2012-09-28", "volume": "117", "pages": "Art. No. B09408" }, { "id": "authors:397rs-r8d33", "collection": "authors", "collection_id": "397rs-r8d33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121023-091349342", "type": "article", "title": "The role of velocity-neutral creep on the modulation of tectonic tremor activity by periodic loading", "author": [ { "family_name": "Ader", "given_name": "Thomas J.", "clpid": "Ader-T-J" }, { "family_name": "Ampuero", "given_name": "Jean-Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Slow slip events and associated non-volcanic tremors are sensitive to oscillatory stress perturbations, such as those induced by tides or seismic surface waves. Slow slip events and tremors are thought to occur near the seismic-aseismic transition regions of active faults, where the difference a \u2212 b = \u2202\u03bc/\u2202lnV between the sensitivity of friction to slip rate and fault state, which characterizes the stability of slip, can be arbitrarily small. We investigate the response of a velocity-strengthening fault region to oscillatory loads through analytical approximations and spring-slider simulations. We find that fault areas that are near velocity-neutral at steady-state, i.e., \u2202\u03bc / \u2202lnV \u2248 0, are highly sensitive to cyclic loads: oscillatory stress perturbations in a certain range of periods induce large transient slip velocities. These aseismic transients can in turn trigger tremor activity with enhanced oscillatory modulation. In this sensitive regime, a harmonic Coulomb stress perturbation of amplitude \u0394S causes a slip rate perturbation varying as e^(\u0394S/(a\u2212b)\u03c3), where \u03c3 is the effective normal stress. This result is in agreement with observations of the relationship between tremor rate and amplitude of stress perturbations for tremors triggered by passing seismic waves. Our model of tremor modulation mediated by transient creep does not require extremely high pore fluid pressure and provides a framework to interpret the sensitivity and phase of tidally modulated tremors observed in Parkfield and Shikoku in terms of spatial variations of friction parameters and background slip rate.", "doi": "10.1029/2012GL052326", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2012-08-28", "series_number": "16", "volume": "39", "issue": "16", "pages": "Art. No. L16310" }, { "id": "authors:714fj-kwe95", "collection": "authors", "collection_id": "714fj-kwe95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120827-114719257", "type": "article", "title": "Sources of shaking and flooding during the Tohoku-Oki earthquake: A mixture of rupture styles", "author": [ { "family_name": "Wei", "given_name": "Shengji", "clpid": "Wei-Shengji" }, { "family_name": "Graves", "given_name": "Robert", "clpid": "Graves-R" }, { "family_name": "Helmberger", "given_name": "Don", "clpid": "Helmberger-D-V" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Jiang", "given_name": "Junle", "orcid": "0000-0002-8796-5846", "clpid": "Jiang-Junle" } ], "abstract": "Modeling strong ground motions from great subduction zone earthquakes is one of the great challenges of computational seismology. To separate the rupture characteristics from complexities caused by 3D sub-surface geology requires an extraordinary data set such as provided by the recent Mw9.0 Tohoku-Oki earthquake. Here we combine deterministic inversion and dynamically guided forward simulation methods to model over one thousand high-rate GPS and strong motion observations from 0 to 0.25 Hz across the entire Honshu Island. Our results display distinct styles of rupture with a deeper generic interplate event (\u223cMw8.5) transitioning to a shallow tsunamigenic earthquake (\u223cMw9.0) at about 25 km depth in a process driven by a strong dynamic weakening mechanism, possibly thermal pressurization. This source model predicts many important features of the broad set of seismic, geodetic and seafloor observations providing a major advance in our understanding of such great natural hazards.", "doi": "10.1016/j.epsl.2012.04.006", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2012-06-01", "volume": "333-334", "pages": "91-100" }, { "id": "authors:sxe19-jbt83", "collection": "authors", "collection_id": "sxe19-jbt83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120731-155300263", "type": "article", "title": "Multi-Link InSAR Time Series: Enhancement of a Wrapped Interferometric Database", "author": [ { "family_name": "Pinel-Puyss\u00e9gur", "given_name": "B\u00e9atrice", "clpid": "Pinel-Puyss\u00e9gur-B" }, { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Ground surface deformation, in particular of tectonic or volcanic origin, might be monitored from time series of SAR interferograms. Conventional approaches require unwrapping of the interferograms. This is most often a limiting factor because the deformation signal is often obscured by decorrelation noise, baseline and topography compensation residuals and atmospheric effects. We present here a method that produces denoised wrapped phase time series. It can be used as a pre-processing to exploit wrapped phase time series or to facilitate unwrapping. The different paths linking two dates are combined in order to derive the most likely estimate of the phase difference between these dates. The result is called a Multi-Link SAR (MuLSAR) interferogram. We demonstrate the performance of the technique on a synthetic database and on a real database of ENVISAT images. The phase standard deviation is reduced from 0.94 rad to 0.60 rad for the synthetic database and from 1.09 rad to 0.89 rad for the real database. In addition to providing denoised interferograms the technique enhances the temporal resolution of an interferometric database as it is possible to compute a MuLSAR from pairs of images for which no interferogram could be produced due to geometric or temporal decorrelation. The method enhances the exploitation of large database especially when affected by temporal decorrelation.", "doi": "10.1109/JSTARS.2012.2196758", "issn": "1939-1404", "publisher": "IEEE", "publication": "IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing", "publication_date": "2012-06", "series_number": "3", "volume": "5", "issue": "3", "pages": "784-794" }, { "id": "authors:pp9qy-h8e28", "collection": "authors", "collection_id": "pp9qy-h8e28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120611-090342699", "type": "article", "title": "Earth-like sand fluxes on Mars", "author": [ { "family_name": "Bridges", "given_name": "N. T.", "orcid": "0000-0002-6790-6793", "clpid": "Bridges-N-T" }, { "family_name": "Ayoub", "given_name": "F.", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Leprince", "given_name": "S.", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Lucas", "given_name": "A.", "clpid": "Lucas-A" }, { "family_name": "Mattson", "given_name": "S.", "clpid": "Mattson-S" } ], "abstract": "Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models, raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies showed sand activity, but could not determine whether entire dunes were moving\u2014implying large sand fluxes\u2014or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.", "doi": "10.1038/nature11022", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2012-05-17", "series_number": "7398", "volume": "485", "issue": "7398", "pages": "339-342" }, { "id": "authors:rknxz-cb876", "collection": "authors", "collection_id": "rknxz-cb876", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120521-080956348", "type": "article", "title": "Under the Hood of the Earthquake Machine: Toward Predictive Modeling of the Seismic Cycle", "author": [ { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-S" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Advances in observational, laboratory, and modeling techniques open the way to the development of physical models of the seismic cycle with potentially predictive power. To explore that possibility, we developed an integrative and fully dynamic model of the Parkfield segment of the San Andreas Fault. The model succeeds in reproducing a realistic earthquake sequence of irregular moment magnitude (M_w) 6.0 main shocks\u2014including events similar to the ones in 1966 and 2004\u2014and provides an excellent match for the detailed interseismic, coseismic, and postseismic observations collected along this fault during the most recent earthquake cycle. Such calibrated physical models provide new ways to assess seismic hazards and forecast seismicity response to perturbations of natural or anthropogenic origins.", "doi": "10.1126/science.1218796", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2012-05-11", "series_number": "6082", "volume": "336", "issue": "6082", "pages": "707-710" }, { "id": "authors:tavqm-6yn80", "collection": "authors", "collection_id": "tavqm-6yn80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120517-092256179", "type": "article", "title": "Convergence rate across the Nepal Himalaya and interseismic coupling on the Main Himalayan Thrust: Implications for seismic hazard", "author": [ { "family_name": "Ader", "given_name": "Thomas", "clpid": "Ader-T" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Liu-Zeng", "given_name": "Jing", "clpid": "Liu-Zeng-Jing" }, { "family_name": "Lyon-Caen", "given_name": "H\u00e9l\u00e8ne", "clpid": "Lyon-Caen-H" }, { "family_name": "Bollinger", "given_name": "Laurent", "clpid": "Bollinger-L" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" }, { "family_name": "Genrich", "given_name": "Jeff", "clpid": "Genrich-J-F" }, { "family_name": "Thomas", "given_name": "Marion", "clpid": "Thomas-M" }, { "family_name": "Chanard", "given_name": "Kristel", "orcid": "0000-0001-9934-9621", "clpid": "Chanard-K" }, { "family_name": "Sapkota", "given_name": "Soma Nath", "clpid": "Sapkota-S-N" }, { "family_name": "Rajaure", "given_name": "Sudhir", "clpid": "Rajaure-S" }, { "family_name": "Shrestha", "given_name": "Prithvi", "clpid": "Shrestha-P" }, { "family_name": "Ding", "given_name": "Lin", "clpid": "Ding-Lin" }, { "family_name": "Flouzat", "given_name": "Mireille", "clpid": "Flouzat-M" } ], "abstract": "We document geodetic strain across the Nepal Himalaya using GPS times series from 30 stations in Nepal and southern Tibet, in addition to previously published campaign GPS points and leveling data and determine the pattern of interseismic coupling on the Main Himalayan Thrust fault (MHT). The noise on the daily GPS positions is modeled as a combination of white and colored noise, in order to infer secular velocities at the stations with consistent uncertainties. We then locate the pole of rotation of the Indian plate in the ITRF 2005 reference frame at longitude = \u2212 1.34\u00b0 \u00b1 3.31\u00b0, latitude = 51.4\u00b0 \u00b1 0.3\u00b0 with an angular velocity of \u03a9 = 0.5029 \u00b1 0.0072\u00b0/Myr. The pattern of coupling on the MHT is computed on a fault dipping 10\u00b0 to the north and whose strike roughly follows the arcuate shape of the Himalaya. The model indicates that the MHT is locked from the surface to a distance of approximately 100 km down dip, corresponding to a depth of 15 to 20 km. In map view, the transition zone between the locked portion of the MHT and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the Himalaya. According to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data, this transition seems to happen in a zone where the temperature reaches 350\u00b0C. The convergence between India and South Tibet proceeds at a rate of 17.8 \u00b1 0.5 mm/yr in central and eastern Nepal and 20.5 \u00b1 1 mm/yr in western Nepal. The moment deficit due to locking of the MHT in the interseismic period accrues at a rate of 6.6 \u00b1 0.4 \u00d7 10^(19) Nm/yr on the MHT underneath Nepal. For comparison, the moment released by the seismicity over the past 500 years, including 14 M_W \u2265 7 earthquakes with moment magnitudes up to 8.5, amounts to only 0.9 \u00d7 10^(19) Nm/yr, indicating a large deficit of seismic slip over that period or very infrequent large slow slip events. No large slow slip event has been observed however over the 20 years covered by geodetic measurements in the Nepal Himalaya. We discuss the magnitude and return period of M > 8 earthquakes required to balance the long term slip budget on the MHT.", "doi": "10.1029/2011JB009071", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2012-04-13", "volume": "117", "pages": "Art. No. B04403" }, { "id": "authors:3y1w4-btm76", "collection": "authors", "collection_id": "3y1w4-btm76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120127-094423904", "type": "article", "title": "Interseismic coupling and seismic potential along the Central\n Andes subduction zone", "author": [ { "family_name": "Chlieh", "given_name": "Mohamed", "clpid": "Chlieh-M" }, { "family_name": "Perfettini", "given_name": "Hugo", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Tavera", "given_name": "Hernando", "clpid": "Tavera-H" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Remy", "given_name": "Dominique", "clpid": "Remy-D" }, { "family_name": "Nocquet", "given_name": "Jean-Mathieu", "clpid": "Nocquet-J-M" }, { "family_name": "Rolandone", "given_name": "Fr\u00e9d\u00e9rique", "clpid": "Rolandone-F" }, { "family_name": "Bondoux", "given_name": "Francis", "clpid": "Bondoux-F" }, { "family_name": "Gabalda", "given_name": "Germinal", "clpid": "Gabalda-G" }, { "family_name": "Bonvalot", "given_name": "Sylvain", "clpid": "Bonvalot-S" } ], "abstract": "We use about two decades of geodetic measurements to characterize interseismic strain build up along the Central Andes subduction zone from Lima, Peru, to Antofagasta, Chile. These measurements are modeled assuming a 3-plate model (Nazca, Andean sliver and South America Craton) and spatially varying interseismic coupling (ISC) on the Nazca megathrust interface. We also determine slip models of the 1996 M_w = 7.7 Nazca, the 2001 M_w = 8.4 Arequipa, the 2007 M_w = 8.0 Pisco and the M_w = 7.7 Tocopilla earthquakes. We find that the data require a highly heterogeneous ISC pattern and that, overall, areas with large seismic slip coincide with areas which remain locked in the interseismic period (with high ISC). Offshore Lima where the ISC is high, a M_w\u223c8.6\u20138.8 earthquake occurred in 1746. This area ruptured again in a sequence of four M_w\u223c8.0 earthquakes in 1940, 1966, 1974 and 2007 but these events released only a small fraction of the elastic strain which has built up since 1746 so that enough elastic strain might be available there to generate a M_w > 8.5 earthquake. The region where the Nazca ridge subducts appears to be mostly creeping aseismically in the interseismic period (low ISC) and seems to act as a permanent barrier as no large earthquake ruptured through it in the last 500 years. In southern Peru, ISC is relatively high and the deficit of moment accumulated since the M_w\u223c8.8 earthquake of 1868 is equivalent to a magnitude M_w\u223c8.4 earthquake. Two asperities separated by a subtle aseismic creeping patch are revealed there. This aseismic patch may arrest some rupture as happened during the 2001 Arequipa earthquake, but the larger earthquakes of 1604 and 1868 were able to rupture through it. In northern Chile, ISC is very high and the rupture of the 2007 Tocopilla earthquake has released only 4% of the elastic strain that has accumulated since 1877. The deficit of moment which has accumulated there is equivalent to a magnitude M_w\u223c8.7 earthquake. This study thus provides elements to assess the location, size and magnitude of future large megathurst earthquakes in the Central Andes subduction zone. Caveats of this study are that interseismic strain of the forearc is assumed time invariant and entirely elastic. Also a major source of uncertainty is due to fact that the available data place very little constraints on interseismic coupling at shallow depth near the trench, except offshore Lima where sea bottom geodetic measurements have been collected suggesting strong coupling.", "doi": "10.1029/2010JB008166", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2011-12-17", "volume": "116", "pages": "Art. No. B12405" }, { "id": "authors:mmpk9-h3m26", "collection": "authors", "collection_id": "mmpk9-h3m26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111006-084146589", "type": "article", "title": "Superficial simplicity of the 2010 El Mayor\u2013Cucapah earthquake of Baja California in Mexico", "author": [ { "family_name": "Wei", "given_name": "Shengji", "clpid": "Wei-Shengji" }, { "family_name": "Fielding", "given_name": "Eric", "orcid": "0000-0002-6648-8067", "clpid": "Fielding-E-J" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Sladen", "given_name": "Anthony", "orcid": "0000-0003-4126-0020", "clpid": "Sladen-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Helmberger", "given_name": "Don", "clpid": "Helmberger-D-V" }, { "family_name": "Hauksson", "given_name": "Egill", "orcid": "0000-0002-6834-5051", "clpid": "Hauksson-E" }, { "family_name": "Chu", "given_name": "Risheng", "clpid": "Chu-Risheng" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Hudnut", "given_name": "Kenneth", "orcid": "0000-0002-3168-4797", "clpid": "Hudnut-K-W" }, { "family_name": "Herring", "given_name": "Thomas", "clpid": "Herring-T" }, { "family_name": "Briggs", "given_name": "Richard", "clpid": "Briggs-R-W" } ], "abstract": "The geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation, propagation and arrest of seismic ruptures. The fault system that runs from southern California into Mexico is a simple strike-slip boundary: the west side of California and Mexico moves northwards with respect to the east. However, the M_w 7.2 2010 El Mayor\u2013Cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike-slip fault. Here we use geodetic, remote-sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake. We find that the earthquake produced a straight 120-km-long fault trace that cut through the Cucapah mountain range and across the Colorado River delta. However, at depth, the fault is made up of two different segments connected by a small extensional fault. Both segments strike N130\u00b0\u2009E, but dip in opposite directions. The earthquake was initiated on the connecting extensional fault and 15\u2009s later ruptured the two main segments with dominantly strike-slip motion. We show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves. We conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone.", "doi": "10.1038/ngeo1213", "issn": "1752-0894", "publisher": "Nature Publishing Group", "publication": "Nature Geoscience", "publication_date": "2011-09", "series_number": "9", "volume": "4", "issue": "9", "pages": "615-618" }, { "id": "authors:tdczk-3y238", "collection": "authors", "collection_id": "tdczk-3y238", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110909-110934158", "type": "article", "title": "The 2001 M_w 7.6 Bhuj earthquake, low fault friction, and the crustal support of plate driving forces in India", "author": [ { "family_name": "Copley", "given_name": "Alex", "clpid": "Copley-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hollingsworth", "given_name": "James", "orcid": "0000-0003-0122-296X", "clpid": "Hollingsworth-J" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" } ], "abstract": "We present a source model for the 2001 M_w 7.6 Bhuj earthquake of northwest India. The slip distribution suggests a high stress drop (~35 MPa) and, together with the depth distribution of aftershocks, that the entire crust is seismogenic. We suggest that the active faults have an effective coefficient of friction of ~0.08, which is sufficient for the seismogenic crust to support the majority of the compressive force transmitted through the Indian lithosphere. This model is consistent with the midcrustal depth of the transition from extension to compression beneath the Ganges foreland basin where India underthrusts southern Tibet. If the coefficient of friction were the more traditional value of 0.6, the lithosphere would be required to support a net force roughly an order of magnitude higher than current estimates in order to match the observed depth of the neutral fiber.", "doi": "10.1029/2010JB008137", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2011-08-19", "volume": "116", "pages": "Art. No. B08405" }, { "id": "authors:pkfe8-wqn69", "collection": "authors", "collection_id": "pkfe8-wqn69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110826-140927554", "type": "article", "title": "Evidence for postseismic deformation of the lower\n crust following the 2004 Mw6.0 Parkfield earthquake", "author": [ { "family_name": "Bruhat", "given_name": "Lucile", "clpid": "Bruhat-L" }, { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Previous studies have shown that postseismic relaxation following the 2004 Mw6.0 Parkfield, CA, earthquake is dominated by afterslip. However, we show that some fraction of the afterslip inferred from kinematic inversion to have occurred immediately below the seismically ruptured area may in fact be a substitute for viscous postseismic deformation of the lower crust. Using continuous GPS and synthetic aperture radar interferometry, we estimate the relative contribution of shallow afterslip (at depth less than 20km) and deeper seated deformation required to account for observed postseismic surface displacements. Exploiting the possible separation in space and time of the time series of displacements predicted from viscoelastic relaxation, we devise a linear inversion scheme that allows inverting jointly for the contribution of afterslip and viscoelastic flow as a function of time. We find that a wide range of models involving variable amounts of viscoelastic deformation can fit the observations equally well provided that they allow some fraction of deep-seated deformation (at depth larger than \u223c20 km). These models require that the moment released by postseismic relaxation over 5 years following the earthquake reached nearly as much as 200% of the coseismic moment. All the models show a remarkable complementarity of coseismic and shallow afterslip distributions. Some significant deformation at lower crustal depth (20\u201326 km) is required to fit the geodetic data. The condition that postseismic deformation cannot exceed complete relaxation places a constraint on the amount of deep seated deformation. The analysis requires an effective viscosity of at least ~10^(18) Pa s of the lower crust (assuming a semi-infinite homogeneous viscous domain). This deep-seated deformation is consistent with the depth range of tremors which also show a transient postseismic response and could explain as much as 50% of the total postseismic geodetic moment (the remaining fraction being due to afterslip at depth shallower than 20 km). Lower crustal postseismic deformation could reflect a combination of localized ductile deformation and aseismic frictional sliding.", "doi": "10.1029/2010JB008073", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2011-08-04", "volume": "116", "pages": "B08401" }, { "id": "authors:nhqab-mps53", "collection": "authors", "collection_id": "nhqab-mps53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110729-090443618", "type": "article", "title": "Earthquakes: The lessons of Tohoku-Oki", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "An exceptional data set documents surface deformation before, during and after\nthe earthquake that struck northeastern Japan in March 2011. But models for\nassessing seismic and tsunami hazard remain inadequate.", "doi": "10.1038/nature10265", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2011-07-21", "series_number": "7356", "volume": "475", "issue": "7356", "pages": "300-301" }, { "id": "authors:f0ghs-jc769", "collection": "authors", "collection_id": "f0ghs-jc769", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110415-142614838", "type": "article", "title": "Evidence for mechanical coupling and strong Indian lower crust beneath southern Tibet", "author": [ { "family_name": "Copley", "given_name": "Alex", "clpid": "Copley-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" } ], "abstract": "How surface deformation within mountain ranges relates to tectonic processes at depth is not well understood. The upper crust of the Tibetan Plateau is generally thought to be poorly coupled to the underthrusting Indian crust because of an intervening low-viscosity channel. Here, however, we show that the contrast in tectonic regime between primarily strike-slip faulting in northern Tibet and dominantly normal faulting in southern Tibet requires mechanical coupling between the upper crust of southern Tibet and the underthrusting Indian crust. Such coupling is inconsistent with the presence of active 'channel flow' beneath southern Tibet, and suggests that the Indian crust retains its strength as it underthrusts the plateau. These results shed new light on the debates regarding the mechanical properties of the continental lithosphere, and the deformation of Tibet.", "doi": "10.1038/nature09926", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2011-04-07", "series_number": "7341", "volume": "472", "issue": "7341", "pages": "79-81" }, { "id": "authors:cvsvc-k2v20", "collection": "authors", "collection_id": "cvsvc-k2v20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110503-151958063", "type": "article", "title": "Paleo-erosion rates in Central Asia since 9 Ma: A transient increase at the onset of Quaternary glaciations?", "author": [ { "family_name": "Charreau", "given_name": "J.", "clpid": "Charreau-J" }, { "family_name": "Blard", "given_name": "P.-H.", "clpid": "Blard-P-H" }, { "family_name": "Puchol", "given_name": "N.", "clpid": "Puchol-N" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lallier-Verg\u00e8s", "given_name": "E.", "clpid": "Lallier-Verg\u00e8s-E" }, { "family_name": "Bourl\u00e8s", "given_name": "D.", "clpid": "Bourl\u00e8s-D" }, { "family_name": "Braucher", "given_name": "R.", "clpid": "Braucher-R" }, { "family_name": "Gallaud", "given_name": "A.", "clpid": "Gallaud-A" }, { "family_name": "Finkel", "given_name": "R.", "clpid": "Finkel-R" }, { "family_name": "Jolivet", "given_name": "M.", "clpid": "Jolivet-M" }, { "family_name": "Chen", "given_name": "Y.", "clpid": "Chen-Yan" }, { "family_name": "Roy", "given_name": "P.", "clpid": "Roy-P" } ], "abstract": "Erosion is a fundamental player of the interactions existing between internal geodynamics and climate, in\nparticular through its influence on the carbon dioxide budget. However, long term (> Ma) erosion rates, estimated indirectly from sediment budget, remain poorly constrained. While some studies suggest that worldwide erosion rates increased at the Plio-Pleistocene climatic transition (~4\u20132 Ma), the validity of this observation and its significance is a matter of debate due to potential biases of the sedimentary record and to the influence of sea level fall on the global sedimentary flux to marginal basins. In the present study, we estimate erosion rates over the last ~9 Ma using in situ produced cosmogenic ^(10)Be concentrations measured in magnetostratigraphically dated continental sediments. We focus on an intracontinental endorheic\nwatershed draining the northern Tianshan in Central Asia, a key region regarding the ongoing debate. While erosion rates between 0.1 and 1 mm\u00b7yr^(\u22121) are derived from most of our record, they reach values as high as ~2.5 mm\u00b7yr^(\u22121) from 2.5 to 1.7 Ma. Then, after 1.7 Ma, recent andmodern erosion rates fell below 1 mm\u00b7yr^(\u22121). This temporary increase is correlated with the onset of Quaternary ice ages and suggests that global climate had a significant and transient impact on erosion.", "doi": "10.1016/j.epsl.2011.01.018", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2011-04-01", "series_number": "1-2", "volume": "304", "issue": "1-2", "pages": "85-92" }, { "id": "authors:4bgnk-n2d35", "collection": "authors", "collection_id": "4bgnk-n2d35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110104-093822416", "type": "article", "title": "PCAIM joint inversion of InSAR and ground-based geodetic time series: Application to monitoring magmatic inflation beneath the Long Valley Caldera", "author": [ { "family_name": "Lin", "given_name": "Yu-nung Nina", "clpid": "Lin-Yu-nung-Nina" }, { "family_name": "Kositsky", "given_name": "Andrew P.", "clpid": "Kositsky-A-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "This study demonstrates the interest of using a Principal Component Analysis-based Inversion Method (PCAIM) to analyze jointly InSAR and ground-based geodetic time series of crustal deformation. A major advantage of this approach is that the InSAR tropospheric biases are naturally filtered out provided they do not introduce correlated or high amplitude noise in the input times series. This approach yields source models which are well-constrained both in time and space due to the temporal resolution of the ground-based geodetic data and the spatial resolution of the InSAR data. The technique is computationally inexpensive allowing for the inversion of large datasets. To demonstrate the performance of this approach, we apply it to the 1997\u201398 magmatic inflation event in the Long Valley Caldera, California.", "doi": "10.1029/2010GL045769", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2010-12", "series_number": "23", "volume": "37", "issue": "23", "pages": "Art. No. L23301" }, { "id": "authors:byx87-cd721", "collection": "authors", "collection_id": "byx87-cd721", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100719-092452020", "type": "article", "title": "Exhumation, crustal deformation, and thermal structure of the Nepal Himalaya derived from the inversion of thermochronological and thermobarometric data and modeling of the topography", "author": [ { "family_name": "Herman", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Herman-F" }, { "family_name": "Copeland", "given_name": "Peter", "clpid": "Copeland-P" }, { "family_name": "Avouac", "given_name": "Jean\u2010Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bollinger", "given_name": "Laurent", "clpid": "Bollinger-L" }, { "family_name": "Mah\u00e9o", "given_name": "Gweltaz", "clpid": "Mah\u00e9o-G" }, { "family_name": "Le Fort", "given_name": "Patrick", "clpid": "Le-Fort-P" }, { "family_name": "Rai", "given_name": "Santaman", "clpid": "Rai-S" }, { "family_name": "Foster", "given_name": "David", "clpid": "Foster-D" }, { "family_name": "P\u00eacher", "given_name": "Arnaud", "clpid": "P\u00eacher-A" }, { "family_name": "St\u00fcwe", "given_name": "Kurt", "clpid": "St\u00fcwe-K" }, { "family_name": "Henry", "given_name": "Pierre", "clpid": "Henry-P" } ], "abstract": "Two end\u2010member kinematic models of crustal shortening across the Himalaya are\ncurrently debated: one assumes localized thrusting along a single major thrust fault, the\nMain Himalayan Thrust (MHT) with nonuniform underplating due to duplexing, and the\nother advocates for out\u2010of\u2010sequence (OOS) thrusting in addition to thrusting along the\nMHT and underplating. We assess these two models based on the modeling of\nthermochronological, thermometric, and thermobarometric data from the central Nepal\nHimalaya. We complement a data set compiled from the literature with 114 ^(40)Ar/^(39)Ar,\n10 apatite fission track, and 5 zircon (U\u2010Th)/He thermochronological data. The data are\npredicted using a thermokinematic model (PECUBE), and the model parameters are\nconstrained using an inverse approach based on the Neighborhood Algorithm. The model\nparameters include geometric characteristics as well as overthrusting rates, radiogenic heat\nproduction in the High Himalayan Crystalline (HHC) sequence, the age of initiation of\nthe duplex or of out-of-sequence thrusting. Both models can provide a satisfactory fit to the\ninverted data. However, the model with out-of-sequence thrusting implies an unrealistic\nconvergence rate \u226530 mm yr^(\u22121). The out-of-sequence thrust model can be adjusted to fit the\nconvergence rate and the thermochronological data if the Main Central Thrust zone is\nassigned a constant geometry and a dip angle of about 30\u00b0 and a slip rate of <1 mm yr^(\u22121). In\nthe duplex model, the 20 mm yr^(\u22121) convergence rate is partitioned between an overthrusting\nrate of 5.8 \u00b1 1.4 mm yr^(\u22121) and an underthrusting rate of 14.2 \u00b1 1.8 mm yr^(\u22121). Modern rock\nuplift rates are estimated to increase from about 0.9 \u00b1 0.31 mm yr^(\u22121) in the Lesser Himalaya to\n3.0 \u00b1 0.9 mm yr^(\u22121) at the front of the high range, 86 \u00b1 13 km from the Main Frontal Thrust.\nThe effective friction coefficient is estimated to be 0.07 or smaller, and the radiogenic\nheat production of HHC units is estimated to be 2.2 \u00b1 0.1 \u00b5Wm^(\u22123). The midcrustal\nduplex initiated at 9.8 \u00b1 1.7 Ma, leading to an increase of uplift rate at front of the High\nHimalaya from 0.9 \u00b1 0.31 to 3.05 \u00b1 0.9 mm yr^(\u22121). We also run 3-D models by coupling\nPECUBE with a landscape evolution model (CASCADE). This modeling shows that the\neffect of the evolving topography can explain a fraction of the scatter observed in the data but\nnot all of it, suggesting that lateral variations of the kinematics of crustal deformation and\nexhumation are likely. It has been argued that the steep physiographic transition at the foot of\nthe Greater Himalayan Sequence indicates OOS thrusting, but our results demonstrate\nthat the best fit duplex model derived from the thermochronological and thermobarometric\ndata reproduces the present morphology of the Nepal Himalaya equally well.", "doi": "10.1029/2008JB006126", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2010-06-24", "volume": "115", "pages": "Art. no. B06407" }, { "id": "authors:zq63n-ppj50", "collection": "authors", "collection_id": "zq63n-ppj50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100526-140621794", "type": "article", "title": "Seismic and aseismic slip on the Central Peru megathrust", "author": [ { "family_name": "Perfettini", "given_name": "Hugo", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Tavera", "given_name": "Hernando", "clpid": "Tavera-H" }, { "family_name": "Kositsky", "given_name": "Andrew", "clpid": "Kositsky-A-P" }, { "family_name": "Nocquet", "given_name": "Jean-Mathieu", "clpid": "Nocquet-J-M" }, { "family_name": "Bondoux", "given_name": "Francis", "clpid": "Bondoux-F" }, { "family_name": "Chlieh", "given_name": "Mohamed", "clpid": "Chlieh-M" }, { "family_name": "Sladen", "given_name": "Anthony", "orcid": "0000-0003-4126-0020", "clpid": "Sladen-A" }, { "family_name": "Audin", "given_name": "Laurence", "clpid": "Audin-L" }, { "family_name": "Farber", "given_name": "Daniel L.", "clpid": "Farber-D-L" }, { "family_name": "Soler", "given_name": "Pierre", "clpid": "Soler-P" } ], "abstract": "Slip on a subduction megathrust can be seismic or aseismic, with the two modes of slip complementing each other in time and space to accommodate the long-term plate motions. Although slip is almost purely aseismic at depths greater than about 40\u2009km, heterogeneous surface strain suggests that both modes of slip occur at shallower depths, with aseismic slip resulting from steady or transient creep in the interseismic and postseismic periods. Thus, active faults seem to comprise areas that slip mostly during earthquakes, and areas that mostly slip aseismically. The size, location and frequency of earthquakes that a megathrust can generate thus depend on where and when aseismic creep is taking place, and what fraction of the long-term slip rate it accounts for. Here we address this issue by focusing on the central Peru megathrust. We show that the Pisco earthquake, with moment magnitude M_w = 8.0, ruptured two asperities within a patch that had remained locked in the interseismic period, and triggered aseismic frictional afterslip on two adjacent patches. The most prominent patch of afterslip coincides with the subducting Nazca ridge, an area also characterized by low interseismic coupling, which seems to have repeatedly acted as a barrier to seismic rupture propagation in the past. The seismogenic portion of the megathrust thus appears to be composed of interfingering rate-weakening and rate-strengthening patches. The rate-strengthening patches contribute to a high proportion of aseismic slip, and determine the extent and frequency of large interplate earthquakes. Aseismic slip accounts for as much as 50\u201370% of the slip budget on the seismogenic portion of the megathrust in central Peru, and the return period of earthquakes with M_w = 8.0 in the Pisco area is estimated to be 250\u2009 years.", "doi": "10.1038/nature09062", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2010-05-06", "series_number": "7294", "volume": "465", "issue": "7294", "pages": "78-81" }, { "id": "authors:b90w9-nqx63", "collection": "authors", "collection_id": "b90w9-nqx63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100526-075511174", "type": "article", "title": "Towards inferring earthquake patterns from geodetic observations of interseismic coupling", "author": [ { "family_name": "Kaneko", "given_name": "Yoshihiro", "orcid": "0000-0003-2342-0131", "clpid": "Kaneko-Yoshihiro" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Ultimately, seismotectonic studies seek to provide ways of assessing the timing, magnitude and spatial extent of future earthquakes. Ample observations document the spatial variability in interseismic coupling, defined as a degree of locking of a fault during the period of stress build-up between seismic events: fully or nearly locked fault patches are often surrounded by aseismically creeping areas. However, it is unclear how these observations could help assess future earthquakes. Here we simulate spontaneous seismic and aseismic fault slip with a fully dynamic numerical model. Our simulations establish the dependence of earthquake rupture patterns and interseismic coupling on spatial variations of fault friction. We consider the long-term evolution of slip on a model fault where two seismogenic, locked segments are separated by an aseismically slipping patch where rupture is impeded. We find that the probability for a large earthquake to break through the rupture-impeding patch is correlated with the interseismic coupling averaged over this patch. In addition, the probability that an earthquake breaks through the rupture-impeding patch and interseismic coupling are both related to fault friction properties through a single non-dimensional parameter. Our study opens the possibility of predicting seismic rupture patterns that a fault system can produce on the basis of observations of its interseismic coupling, and suggests that regions of low interseismic coupling may reveal permanent barriers to large earthquakes.", "doi": "10.1038/NGEO843", "issn": "1752-0894", "publisher": "Nature Publishing Group", "publication": "Nature Geoscience", "publication_date": "2010-05", "series_number": "5", "volume": "3", "issue": "5", "pages": "363-369" }, { "id": "authors:2x4x7-ska96", "collection": "authors", "collection_id": "2x4x7-ska96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100413-094606252", "type": "article", "title": "India-Asia collision and the Cenozoic slowdown of the Indian plate: Implications for the forces driving plate motions", "author": [ { "family_name": "Copley", "given_name": "Alex", "clpid": "Copley-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Royer", "given_name": "Jean-Yves", "clpid": "Royer-J-Y" } ], "abstract": "The plate motion of India changed dramatically between 50 and 35 Ma, with the rate of convergence between India and Asia dropping from ~15 to ~4 cm/yr. This change is coincident with the onset of the India-Asia collision, and with a rearrangement of plate boundaries in the Indian Ocean. On the basis of a simple model for the forces exerted upon the edges of the plate and the tractions on the base of the plate, we perform force balance calculations for the precollision and postcollision configurations. We show that the observed Euler poles for the Indian plate are well explained in terms of their locations and magnitudes if (1) the resistive force induced by mountain building in the Himalaya-Tibet area is ~5\u20136 \u00d7 10^(12) N/m, (2) the net force exerted upon the Indian plate by subduction zones is similar in magnitude to the ridge-push force (~2.5 \u00d7 10^(12) N/m), and (3) basal tractions exert a resisting force that is linearly proportional to the plate velocity in the hot spot reference frame. The third point implies an asthenospheric viscosity of ~2\u20135 \u00d7 10^(19) Pa s, assuming a thickness of 100\u2013150 km. Synthetic Euler poles show that crustal thickening in the Tibetan Plateau was the dominant cause of the Cenozoic slowdown of the Indian plate.", "doi": "10.1029/2009JB006634", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2010-03-17", "series_number": "B3", "volume": "115", "issue": "B3", "pages": "Art. No. B03410" }, { "id": "authors:2bsma-fx205", "collection": "authors", "collection_id": "2bsma-fx205", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100405-095913118", "type": "article", "title": "Inverting geodetic time series with a principal component analysis-based inversion method", "author": [ { "family_name": "Kositsky", "given_name": "A. P.", "clpid": "Kositsky-A-P" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The Global Positioning System (GPS) system now makes it possible to monitor deformation of the Earth's surface along plate boundaries with unprecedented accuracy. In theory, the spatiotemporal evolution of slip on the plate boundary at depth, associated with either seismic or aseismic slip, can be inferred from these measurements through some inversion procedure based on the theory of dislocations in an elastic half-space. We describe and test a principal component analysis-based inversion method (PCAIM), an inversion strategy that relies on principal component analysis of the surface displacement time series. We prove that the fault slip history can be recovered from the inversion of each principal component. Because PCAIM does not require externally imposed temporal filtering, it can deal with any kind of time variation of fault slip. We test the approach by applying the technique to synthetic geodetic time series to show that a complicated slip history combining coseismic, postseismic, and nonstationary interseismic slip can be retrieved from this approach. PCAIM produces slip models comparable to those obtained from standard inversion techniques with less computational complexity. We also compare an afterslip model derived from the PCAIM inversion of postseismic displacements following the 2005 8.6 Nias earthquake with another solution obtained from the extended network inversion filter (ENIF). We introduce several extensions of the algorithm to allow statistically rigorous integration of multiple data sources (e.g., both GPS and interferometric synthetic aperture radar time series) over multiple timescales. PCAIM can be generalized to any linear inversion algorithm.", "doi": "10.1029/2009JB006535", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2010-03-03", "series_number": "B3", "volume": "115", "issue": "B3", "pages": "B03401" }, { "id": "authors:155at-kc928", "collection": "authors", "collection_id": "155at-kc928", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100303-095450402", "type": "article", "title": "Source model of the 2007 M_w 8.0 Pisco, Peru earthquake: Implications for seismogenic behavior of subduction megathrusts", "author": [ { "family_name": "Sladen", "given_name": "A.", "orcid": "0000-0003-4126-0020", "clpid": "Sladen-A" }, { "family_name": "Tavera", "given_name": "H.", "clpid": "Tavera-H" }, { "family_name": "Simons", "given_name": "M.", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Konca", "given_name": "A. O.", "clpid": "Konca-A-O" }, { "family_name": "Perfettini", "given_name": "H.", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Audin", "given_name": "L.", "clpid": "Audin-L" }, { "family_name": "Fielding", "given_name": "E. J.", "orcid": "0000-0002-6648-8067", "clpid": "Fielding-E-J" }, { "family_name": "Ortega", "given_name": "F.", "clpid": "Ortega-F" }, { "family_name": "Cavagnoud", "given_name": "R.", "clpid": "Cavagnoud-R" } ], "abstract": "We use Interferometric Synthetic Aperture Radar, teleseismic body waves, tsunami waveforms recorded by tsunameters, field observations of coastal uplift, subsidence, and runup to develop and test a refined model of the spatiotemporal history of slip during the M_w 8.0 Pisco earthquake of 15 August 2007. Our preferred solution shows two distinct patches of high slip. One patch is located near the epicenter while another larger patch ruptured 60 km further south, at the latitude of the Paracas peninsula. Slip on the second patch started 60 s after slip initiated on the first patch. We observed a remarkable anticorrelation between the coseismic slip distribution and the aftershock distribution determined from the Peruvian seismic network. The proposed source model is compatible with regional runup measurements and open ocean tsunami records. From the latter data set, we identified the 12 min timing error of the tsunami forecast system as being due to a mislocation of the source, caused by the use of only one tsunameter located in a nonoptimal azimuth. The comparison of our source model with the tsunami observations validate that the rupture did not extend to the trench and confirms that the Pisco event is not a tsunami earthquake despite its low apparent rupture velocity (<1.5 km/s). We favor the interpretation that the earthquake consists of two subevents, each with a conventional rupture velocity (2\u20134 km/s). The delay between the two subevents might reflect the time for the second shock to nucleate or, alternatively, the time it took for afterslip to increase the stress level on the second asperity to a level necessary for static triggering. The source model predicts uplift offshore and subsidence on land with the pivot line following closely the coastline. This pattern is consistent with our observation of very small vertical displacement along the shoreline when we visited the epicentral area in the days following the event. This earthquake represents, to our knowledge, one of the best examples of a link between the geomorphology of the coastline and the pattern of surface deformation induced by large interplate ruptures.", "doi": "10.1029/2009JB006429", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research F", "publication_date": "2010-02-09", "volume": "115", "pages": "B02405" }, { "id": "authors:d6t66-66p49", "collection": "authors", "collection_id": "d6t66-66p49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100225-110542388", "type": "article", "title": "Rupture Process of the 1999 M_w 7.1 Duzce Earthquake from Joint Analysis of SPOT, GPS, InSAR, Strong-Motion, and Teleseismic Data: A Supershear Rupture with Variable Rupture Velocity", "author": [ { "family_name": "Konca", "given_name": "A. Ozgun", "clpid": "Konca-A-O" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Helmberger", "given_name": "Don V.", "clpid": "Helmberger-D-V" } ], "abstract": "We analyze the rupture process of the 1999 M_w 7.1 Duzce earthquake using seismological, remote sensing, and geodetic data. Ground deformation measured from the subpixel cross correlation of Satellite Pour l'Observation de la Terre (SPOT) images reveals a 55 km long fault trace and smooth surface-slip distribution peaking at 3.5\u20134 m. The westernmost segment overlaps for over 10 km with ruptures from the M_w 7.4 Izmit earthquake. The 15 km long easternmost segment, which cuts across mountainous topography, had not been reported previously. We determine a well-constrained source model using a four-segment fault geometry using constraints on surface fault slip and inverting Global Positioning System and Interferometric Synthetic Aperture Radar data along with strong-motion records. Our results show that some variability of the rupture velocity and an eastward supershear velocity are required to fit the strong-motion data. The rise time, up to 6 sec, correlates with cumulative slip, suggesting a sliding velocity of about 1 m/sec. The source model predicts teleseismic waveforms well, although early by 2 sec. This time shift is probably due to the weak beginning of the earthquake that is not observable at teleseismic distances. Strong-motion records are relatively well predicted from a source model derived from the teleseismic data using the fault geometry derived from the satellite images. This study demonstrates the benefit of using accurate fault geometries to determine finite-fault source models.", "doi": "10.1785/0120090072", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2010-02-01", "series_number": "1", "volume": "100", "issue": "1", "pages": "267-288" }, { "id": "authors:gj0y2-wsr37", "collection": "authors", "collection_id": "gj0y2-wsr37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100119-133059574", "type": "article", "title": "Co-registration and correlation of aerial photographs for ground deformation measurements", "author": [ { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We describe and test a procedure to accurately co-register and correlate multi-temporal aerial images. We show that this procedure can be used to measure surface deformation, and explore the performance and limitations of the technique. The algorithms were implemented in a software package, COSI-Corr (available from the Caltech Tectonics Observatory website). The technique is validated on several case examples of co-seismic deformation. First, we measure co-seismic ground deformation due to the 1992, Mw 7.3, Landers, California, earthquake from 1 m resolution aerial photography of the National Aerial Photography Program (United States Geological Survey). The fault ruptures are clearly detected, including small kilometric segments with fault slip as small as a few tens of centimeters. We also obtained similar performance from images of the fault ruptures produced by the 1999 Mw 7.1 Hector Mine, California, earthquake. The measurements are shown to be biased due to the inaccuracy of the Digital Elevation Model, film distortions, scanning artifacts, and ignorance of ground displacements at the location of the tie points used to co-register the multi-temporal images. We show that some of these artifacts can be identified and corrected.", "doi": "10.1016/j.isprsjprs.2009.03.005", "issn": "0924-2716", "publisher": "Elsevier", "publication": "ISPRS Journal of Photogrammetry and Remote Sensing", "publication_date": "2009-11", "series_number": "6", "volume": "64", "issue": "6", "pages": "551-560" }, { "id": "authors:02ag5-hb303", "collection": "authors", "collection_id": "02ag5-hb303", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091029-112404757", "type": "article", "title": "The 2005 Ilan earthquake doublet and seismic crisis in northeastern Taiwan: evidence for dyke intrusion associated with on-land propagation of the Okinawa Trough", "author": [ { "family_name": "Lai", "given_name": "Kuang-Yin", "clpid": "Lai-Kuang-Yin" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" }, { "family_name": "Wu", "given_name": "Yih-Min", "clpid": "Wu-Yih-Min" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Kuo", "given_name": "Yu-Ting", "clpid": "Kuo-Yu-Ting" }, { "family_name": "Wang", "given_name": "Yu", "orcid": "0000-0003-3589-9274", "clpid": "Wang-Yu" }, { "family_name": "Chang", "given_name": "Chien-Hsin", "clpid": "Chang-Chien-Hsin" }, { "family_name": "Lin", "given_name": "Kuan-Chuan", "clpid": "Lin-Kuan-Chuan" } ], "abstract": "Northern Taiwan underwent mountain building in the early stage of the Taiwan orogeny but is currently subjected to post-collisional crustal extension. It may be related to gravitational collapse or to the rifting of the Okinawa Trough, which lies offshore northeastern Taiwan. The Ilan Plain, northeastern Taiwan, which is bounded by the normal fault systems and filled up with thick Pliocene\u2013Pleistocene sedimentary sequences, formed under such an extension environment. Over there on 2005 March 5 two earthquakes with about the same magnitude (M_L = 5.9) occurred within 68 s and produced intense aftershocks activity according to the records of Central Weather Bureau Seismic Network of Taiwan. We relocated the earthquake sequence by the three-dimension earthquake location algorithm with the newly published 3-D Vp and Vp/Vs velocity model, and determined the first-polarity focal mechanisms of the earthquake doublet. One major cluster of aftershocks which trends E\u2013W and dips steeply to the south can be identified and picked up as a potential fault plane. The focal mechanisms of the two main shocks are both classified as normal type by first-polarity but strike-slip by centroid moment tensor inversion; however two methods both yield consistent E\u2013W strike. Static coseismic deformation was additionally determined from Global Positioning System (GPS) daily solutions at a set of continuous GPS stations and from strong-motion seismographs. These data show NW\u2013SE extension at high angle to the fault plane, which cannot be explained from a simple strike-slip double-couple mechanism. On the other hand, the small vertical displacements and steep fault plane cannot be explained from a simple normal event as well. We present from elastic dislocation modelling that the geodetic data are best explained by significant component of tensile source with centimetre-scale of opening on a 15-km-long fault extending from 1 to 13 km depth. We therefore interpret the crisis as the result of dyke intrusion at the very tip of the Okinawa Trough, which is reasonably driven by backarc spreading.", "doi": "10.1111/j.1365-246X.2009.04307.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2009-11", "series_number": "2", "volume": "179", "issue": "2", "pages": "678-686" }, { "id": "authors:6rfgf-ph417", "collection": "authors", "collection_id": "6rfgf-ph417", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091209-095229076", "type": "article", "title": "The Neogene Xiyu Formation, a diachronous prograding gravel wedge at front of the Tianshan: Climatic and tectonic implications", "author": [ { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Gumiaux", "given_name": "Charles", "clpid": "Gumiaux-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Augier", "given_name": "Romain", "clpid": "Augier-R" }, { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Barrier", "given_name": "Laurie", "clpid": "Barrier-L" }, { "family_name": "Gilder", "given_name": "Stuart", "clpid": "Gilder-S" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Charles", "given_name": "Nicolas", "clpid": "Charles-N" }, { "family_name": "Wang", "given_name": "Qingchen", "clpid": "Wang-Qingchen" } ], "abstract": "The Tarim and Junggar basins in central Asia are capped by a thick pile of conglomerates, called the Xiyu\nFormation, that are commonly linked to a change in climate and/or accelerated uplift near the Plio-\nPleistocene boundary. In order to better understand their origin and significance, we carried out a combined\nstructural and magnetostratigraphic study in the Quilitage syncline (southern Tianshan), where the base of\nthe Xiyu conglomerates is observed at both sides of the syncline. A balanced cross-section shows that, even\nat a local-scale, the base of the Xiyu conglomerates cannot be regarded as a single continuous stratigraphic\nlayer. On the southern flank of the Quilitage syncline, we collected 172 samples collected for\nmagnetostratigraphic dating identify 17 polarity chrons that date the new section from 5.2 to ~1.7 Ma\nand constrain the base of the Xiyu conglomerate here at ~1.7 Ma. This is 4.2 Ma younger than the age of the\nXiyu previously found on the northern limb of the same syncline. Together with other magnetostratigraphic\nstudies carried out around the Tianshan, our study unambiguously demonstrates that the onset of deposition\nof the Xiyu conglomerates is diachronous, and that the conglomerates are systematically younger toward the\nbasin. Consequently, the Xiyu Formation should not be considered as a chronostratigraphic marker related to\nany particular tectonic or climatic event, but is instead a prograding gravel wedge that has prograded over\nthe underthrusting forelands. A synthesis of chronologic and structural results yields progradation rates over\nthe last 10 Ma on the order of ~2.0 mm/yr and ~3.9 mm/yr south and north of the Tianshan Mountains\nrespectively. These rates are comparable to the shortening rate across the Tianshan range, suggesting that\nunderthrusting is the main factor governing the progradation rate of the Xiyu Formation.", "doi": "10.1016/j.epsl.2009.07.035", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2009-10-15", "series_number": "3-4", "volume": "287", "issue": "3-4", "pages": "298-310" }, { "id": "authors:f09t5-jbm06", "collection": "authors", "collection_id": "f09t5-jbm06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091020-152813715", "type": "article", "title": "Spatio-temporal Slip, and Stress Level on the Faults within the Western Foothills of Taiwan: Implications for Fault Frictional Properties", "author": [ { "family_name": "Hsu", "given_name": "Ya-Ju", "clpid": "Hsu-Y-J" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Yu", "given_name": "Shui-Beih", "clpid": "Yu-S-B" }, { "family_name": "Chang", "given_name": "Chien-Hsin", "clpid": "Chang-C-H" }, { "family_name": "Wu", "given_name": "Yih-Min", "clpid": "Wu-Y-M" }, { "family_name": "Woessner", "given_name": "Jochen", "clpid": "Woessner-J" } ], "abstract": "We use preseismic, coseismic, and postseismic GPS data of the 1999 Chi-Chi earthquake to infer spatio-temporal variation of fault slip and frictional behavior on the Chelungpu fault. The geodetic data shows that coseismic slip during the Chi-Chi earthquake occurred within a patch that was locked in the period preceding the earthquake, and that afterslip occurred dominantly downdip from the ruptured area. To first-order, the observed pattern and the temporal evolution of afterslip is consistent with models of the seismic cycle based on rate-and-state friction. Comparison with the distribution of temperature on the fault derived from thermo-kinematic modeling shows that aseismic slip becomes dominant where temperature is estimated to exceed 200\u00b0 at depth. This inference is consistent with the temperature induced transition from velocity-weakening to velocity-strengthening friction that is observed in laboratory experiments on quartzo-feldspathic rocks. The time evolution of afterslip is consistent with afterslip being governed by velocity-strengthening frictional sliding. The dependency of friction, \u03bc, on the sliding velocity, V, is estimated to be \u2202\u03bc/\u2202ln V = 8 \u00d7 10^(-3). We report an azimuthal difference of about 10\u201320\u00b0 between preseismic and postseismic GPS velocities, which we interpret to reflect the very low shear stress on the creeping portion of the d\u00e9collement beneath the Central Range, of the order of 1\u20133 MPa, implying a very low friction of about 0.01. This study highlights the importance of temperature and pore pressure in determining fault frictional sliding.", "doi": "10.1007/s00024-009-0510-5", "issn": "0033-4553", "publisher": "Springer", "publication": "Pure and Applied Geophysics", "publication_date": "2009-10", "series_number": "10-11", "volume": "166", "issue": "10-11", "pages": "1853-1884" }, { "id": "authors:9g9ak-sj141", "collection": "authors", "collection_id": "9g9ak-sj141", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090828-231037041", "type": "article", "title": "Investigating tropospheric effects and seasonal position variations in GPS and DORIS time-series from the Nepal Himalaya", "author": [ { "family_name": "Flouzat", "given_name": "Mireille", "clpid": "Flouzat-M" }, { "family_name": "Bettinelli", "given_name": "Pierre", "clpid": "Bettinelli-P" }, { "family_name": "Willis", "given_name": "Pascal", "clpid": "Willis-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "H\u00e9ritier", "given_name": "Thierry", "clpid": "H\u00e9ritier-T" }, { "family_name": "Gautam", "given_name": "Umesh", "clpid": "Gautam-U" } ], "abstract": "Geodetic time-series from continuous GPS (cGPS) and 1 DORIS stations across the Himalaya of central Nepal show strong seasonal fluctuations observed on the horizontal and vertical components. Because the fluctuations determined at the different stations have similar phase but different amplitudes, these observations would imply that the secular shortening across the range is modulated by a seasonal strain. Given the geographic and climatic setting, there is however a possibility that the GPS positions be biased by tropospheric effects. We process these data using two different software packages and two different analysis strategies. Our analysis shows evidence for 1-strong seasonal fluctuation of zenithal delays consistent with in situ meteorological data and two strong horizontal tropospheric gradients in particular in the EW direction, that is, parallel to the mountain front at Gumba, also detected in DORIS results. We show that the tropospheric effects cannot however be the source of the observed seasonality of horizontal strain. This study supports the view that the seasonal strain in the Himalaya is real and probably driven by seasonal surface load variations. Our study adds support to the view that seasonal variations of seismicity in the Himalaya reflects seasonal variations of geodetic strain.", "doi": "10.1111/j.1365-246X.2009.04252.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2009-09", "series_number": "3", "volume": "178", "issue": "3", "pages": "1246-1259" }, { "id": "authors:7crcs-gg753", "collection": "authors", "collection_id": "7crcs-gg753", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120904-144429691", "type": "article", "title": "Continuous thermal histories from muscovite ^(40)Ar/^(39)Ar age spectra", "author": [ { "family_name": "Harrison", "given_name": "T. M.", "clpid": "Harrison-T-M" }, { "family_name": "Heizler", "given_name": "M. T.", "clpid": "Heizler-M-T" }, { "family_name": "Haviv", "given_name": "I.", "clpid": "Haviv-I" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The recent recognition that ^(40)Ar/^(39)Ar age spectra and ^(39)Ar\nArrhenius plots derived from vacuum step-heating of white\nmicas correspond to simple diffusion theory [1] leaves open\nthe possibility that continuous thermal histories can be\nextracted from muscovite via the multi-diffusion domain\n(MDD) model [2] instead of only a single T-t datum. If so,\nthen terranes not previously accessible to high resolution\nthermochronometry (e.g., low grade regional metamorphism)\ncould routinely access vastly improved T-t histories leading to\nrefined tectonic interpretations. We followed up our\nexperimental study [1] by applying laboratory heating\nprotocols designed to maximize the extraction of kinetic\ninformation to white mica separates from a N-S transect across\nthe Main Central Thrust, Arun Valley, Nepal. Most ^(40)Ar/^(39)Ar\nspectra reveal internal age gradients that we interpret to reflect\n^(40)Ar* retention during protracted cooling due to tectonic\nactivity. The age and log (r/r_o) spectra show clear correlations\n\ufffd remarkable considering that the latter is not calculated from\n^(40)Ar release \ufffd confirming that muscovite can retain Ar\ndiffusion boundaries and mechanisms during vacuum stepheating\nthat define the natural retentivity. Using recently\npublished Arrhenius parameters for Ar diffusion in muscovite\n(E = 64 kcal/mol, D_o = 4 cm^2/s; [1]), these gradients reflect\nintragrain closure between ~425 and 280\u00b0C. That muscovite is\namenable to MDD treatment places additional requirements on\nmineral separation practices. For example, the decision to\nreduce grain size in order to eliminate composite grains in the\nanalyzed aliquot needs to be balanced against the requirement\nthat the largest diffusion domain in the sample remain intact.\nThe generality of our conclusion regarding MDD analysis of\nmuscovite to other geologic environments remains to be\ntested. However, the numerous observations of staircase-type\n^(40)Ar/^(39)Ar age spectra of white micas from accretionary,\nanchimetamorphic and granitoid terranes suggest that this\nbehavior is intrinsic to the mineral. The MDD approach\napplied to white micas has tremendous potential to increase\nthe application of continuous, high resolution ^(40)Ar/^(39)Ar\nthermochronology to virtually all crustal provinces.", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2009-06", "series_number": "13", "volume": "73", "issue": "13", "pages": "A497" }, { "id": "authors:5ry7w-fcj85", "collection": "authors", "collection_id": "5ry7w-fcj85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090721-095714948", "type": "article", "title": "Neogene uplift of the Tian Shan Mountains observed in the magnetic record of the Jingou River section (northwest China)", "author": [ { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Gilder", "given_name": "Stuart", "clpid": "Gilder-S" }, { "family_name": "Barrier", "given_name": "Laurie", "clpid": "Barrier-L" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Augier", "given_name": "Romain", "clpid": "Augier-R" }, { "family_name": "Sen", "given_name": "Sevket", "clpid": "Sen-Sevket" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Gallaud", "given_name": "Audrey", "clpid": "Gallaud-A" }, { "family_name": "Graveleau", "given_name": "Fabien", "clpid": "Graveleau-F" }, { "family_name": "Wang", "given_name": "Qingchen", "clpid": "Wang-Qingchen" } ], "abstract": "The Tian Shan Mountains constitute central Asia's longest and highest mountain range. Understanding their Cenozoic uplift history thus bears on mountain building processes in general, and on how deformation has occurred under the influence of the India-Asia collision in particular. In order to help decipher the uplift history of the Tian Shan, we collected 970 samples for magnetostratigraphic analysis along a 4571-m-thick section at the Jingou River (Xinjiang Province, China). Stepwise alternating field and thermal demagnetization isolate a linear magnetization component that is interpreted as primary. From this component, a magnetostratigraphic column composed of 67 polarity chrons are correlated with the reference geomagnetic polarity timescale between \u223c1 Ma and \u223c23.6 Ma, with some uncertainty below \u223c21 Ma. This correlation places precise temporal control on the Neogene stratigraphy of the southern Junggar Basin and provides evidence for two significant stepwise increases in sediment accumulation rate at \u223c16\u201315 Ma and \u223c11\u201310 Ma. Rock magnetic parameters also undergo important changes at \u223c16\u201315 Ma and \u223c11\u201310 Ma that correlate with changes in sedimentary depositional environments. Together with previous work, we conclude that growth history of the modern Tian Shan Mountains includes two pulses of uplift and erosion at \u223c16\u201315 Ma and \u223c11\u201310 Ma. Middle to upper Tertiary rocks around the Tian Shan record very young (<\u223c5 Ma) counterclockwise paleomagnetic rotations, on the order of 15\u00b0 to 20\u00b0, which are interpreted as because of strain partitioning with a component of sinistral shear that localized rotations in the piedmont.", "doi": "10.1029/2007TC002137", "issn": "0278-7407", "publisher": "American Geophysical Union", "publication": "Tectonics", "publication_date": "2009-03-31", "series_number": "2", "volume": "28", "issue": "2", "pages": "TC2008" }, { "id": "authors:dhz5d-fxp85", "collection": "authors", "collection_id": "dhz5d-fxp85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:KONnat08", "type": "article", "title": "Partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence", "author": [ { "family_name": "Konca", "given_name": "A. Ozgun", "clpid": "Konca-A-Ozgun" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sladen", "given_name": "Anthony", "orcid": "0000-0003-4126-0020", "clpid": "Sladen-A" }, { "family_name": "Meltzner", "given_name": "Aron J.", "orcid": "0000-0002-2955-0896", "clpid": "Meltzner-A-J" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Fang", "given_name": "Peng", "clpid": "Fang-Peng" }, { "family_name": "Li", "given_name": "Zhenhong", "clpid": "Li-Zhenhong" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" }, { "family_name": "Genrich", "given_name": "Jeff", "clpid": "Genrich-J-F" }, { "family_name": "Chlieh", "given_name": "Mohamed", "clpid": "Chlieh-M" }, { "family_name": "Natawidjaja", "given_name": "Danny", "clpid": "Natawidjaja-D-H" }, { "family_name": "Bock", "given_name": "Yehuda", "clpid": "Bock-Y" }, { "family_name": "Fielding", "given_name": "Eric J.", "orcid": "0000-0002-6648-8067", "clpid": "Fielding-E-J" }, { "family_name": "Ji", "given_name": "Chen", "orcid": "0000-0002-0350-5704", "clpid": "Ji-Chen" }, { "family_name": "Helmberger", "given_name": "Don V.", "clpid": "Helmberger-D-V" } ], "abstract": "The great Sumatra\u2013Andaman earthquake and tsunami of 2004 was a dramatic reminder of the importance of understanding the seismic and tsunami hazards of subduction zones [1,2,3,4]. In March 2005, the Sunda megathrust ruptured again, producing an event [5] of moment magnitude (Mw) 8.6 south of the 2004 rupture area, which was the site of a similar event in 1861 (ref. 6). Concern was then focused on the Mentawai area, where large earthquakes had occurred in 1797 (Mw = 8.8) and 1833 (Mw = 9.0) [6,7]. Two earthquakes, one of Mw = 8.4 and, twelve hours later, one of Mw = 7.9, indeed occurred there on 12 September 2007. Here we show that these earthquakes ruptured only a fraction of the area ruptured in 1833 and consist of distinct asperities within a patch of the megathrust that had remained locked in the interseismic period. This indicates that the same portion of a megathrust can rupture in different patterns depending on whether asperities break as isolated seismic events or cooperate to produce a larger rupture. This variability probably arises from the influence of non-permanent barriers, zones with locally lower pre-stress due to the past earthquakes. The stress state of the portion of the Sunda megathrust that had ruptured in 1833 and 1797 was probably not adequate for the development of a single large rupture in 2007. The moment released in 2007 amounts to only a fraction both of that released in 1833 and of the deficit of moment that had accumulated as a result of interseismic strain since 1833. The potential for a large megathrust event in the Mentawai area thus remains large.", "doi": "10.1038/nature07572", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2008-12-04", "series_number": "7222", "volume": "456", "issue": "7222", "pages": "631-635" }, { "id": "authors:nma39-3v105", "collection": "authors", "collection_id": "nma39-3v105", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:CHAg08", "type": "article", "title": "Miocene to present kinematics of fault-bend folding across the Huerguosi anticline, northern Tianshan (China), derived from structural, seismic, and magnetostratigraphic data", "author": [ { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Gilder", "given_name": "Stuart", "clpid": "Gilder-S" } ], "abstract": "We combine surface structural measurements, subsurface seismic imaging, and magnetostratigraphic dating to retrieve, through geometric modeling, the detailed history of fold growth and sedimentation across the Huerguosi anticline, on the northern Tianshan piedmont, taking advantage of a beautifully exposed section of growth strata. The model assumes a fault-bend folding mechanism, consistent with subsurface fold geometry. The shortening history is obtained by least-squares fi tting of the measured dip angles of the growth strata. The shortening rate across the anticline is shown to have been remarkably constant: it increased only slightly from 0.84 \u00b1 0.04 mm/yr between 10 and 4 Ma to 1.14 \u00b1 0.02 mm/yr over the past 4 m.y. This approach also allows correcting syntectonic sedimentation rates for the effect of the fold growth and shows that the sedimentation rates in the piggyback basin increased abruptly from ~0.4 to ~0.7 mm/yr ca. 4 Ma.", "doi": "10.1130/G25073A.1", "issn": "0091-7613", "publisher": "Geological Society of America", "publication": "Geology", "publication_date": "2008-11", "series_number": "11", "volume": "36", "issue": "11", "pages": "871-874" }, { "id": "authors:j8h5j-8vt22", "collection": "authors", "collection_id": "j8h5j-8vt22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LEPieeetgrs08", "type": "article", "title": "In-Flight CCD Distortion Calibration for Pushbroom Satellites Based on Subpixel Correlation", "author": [ { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Mus\u00e9", "given_name": "Pablo", "clpid": "Mus\u00e9-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We describe a method that allows for accurate inflight calibration of the interior orientation of any pushbroom camera and that in particular solves the problem of modeling the distortions induced by charge coupled device (CCD) misalignments. The distortion induced on the ground by each CCD is measured using subpixel correlation between the orthorectified image to be calibrated and an orthorectified reference image that is assumed distortion free. Distortions are modeled as camera defects, which are assumed constant over time. Our results show that in-flight interior orientation calibration reduces internal camera biases by one order of magnitude. In particular, we fully characterize and model the Satellite Pour l'Observation de la Terre (SPOT) 4-HRV1 sensor, and we conjecture that distortions mostly result from the mechanical strain produced when the satellite was launched rather than from effects of on-orbit thermal variations or aging. The derived calibration models have been integrated to the software package Coregistration of Optically Sensed Images and Correlation (COSI-Corr), freely available from the Caltech Tectonics Observatory website. Such calibration models are particularly useful in reducing biases in digital elevation models (DEMs) generated from stereo matching and in improving the accuracy of change detection algorithms.", "doi": "10.1109/TGRS.2008.918649", "issn": "0196-2892", "publisher": "IEEE", "publication": "IEEE Transactions on Geoscience and Remote Sensing", "publication_date": "2008-09", "series_number": "9", "volume": "46", "issue": "9", "pages": "2675-2683" }, { "id": "authors:34cma-m7f73", "collection": "authors", "collection_id": "34cma-m7f73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120904-153449230", "type": "article", "title": "Detecting co-seismic displacements in glaciated regions: An example from the great\n November 2002 Denali earthquake using SPOT horizontal offsets", "author": [ { "family_name": "Taylor", "given_name": "Michael H.", "clpid": "Taylor-M-H" }, { "family_name": "Leprince", "given_name": "Sebastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "abstract": "We use SPOT image pairs to determine horizontal offsets associated with the Mw 7.9 November 2002 Denali earthquake in the vicinity of Slate Creek, AK. Field measurements and aerial photographs are used to further characterize the geometry of the surface rupture. Aerial photographs show that shear localization occurs where the rupture trace is linear, and distributed off-fault deformation is common at fault bends and step-overs, or at geologic contacts between rock, glacial sediments, and ice. The displacement field is generated using a sub-pixel cross correlation technique between SPOT images taken before and after the earthquake. We identify the effects of glacier motion in order to isolate the tectonic displacements associated with the Denali earthquake. The resulting horizontal displacement field shows an along-strike variation in dextral shear, with a maximum of approximately 7.5 m in the east near 144\u00b0 52\u2032W, which decreases to about 5 m to the west near 145\u00b0 45\u2032W. If the November 2002 earthquake represents the long-term behavior of the Denali fault, it implies a westward decrease in the long-term dextral slip rate. A possible mechanism to accommodate the westward decreasing slip on the Denali fault is to transfer fault slip to adjacent east-trending contractional structures in the western region of the central Alaskan Range.", "doi": "10.1016/j.epsl.2008.03.028", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2008-06-30", "series_number": "3-4", "volume": "270", "issue": "3-4", "pages": "209-220" }, { "id": "authors:591y8-pb567", "collection": "authors", "collection_id": "591y8-pb567", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101112-140946637", "type": "article", "title": "Heterogeneous coupling of the Sumatran megathrust constrained by geodetic and paleogeodetic measurements", "author": [ { "family_name": "Chlieh", "given_name": "M.", "clpid": "Chlieh-M" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sieh", "given_name": "K.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Natawidjaja", "given_name": "D. H.", "clpid": "Natawidjaja-D-H" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" } ], "abstract": "Geodetic and paleogeodetic measurements of interseismic strain above the Sumatran portion of the Sunda subduction zone reveal a heterogeneous pattern of coupling. Annual banding in corals provides vertical rates of deformation spanning the last half of the 20th century, and repeated GPS surveys between 1991 and 2001 and continuous measurements at GPS stations operated since 2002 provide horizontal velocities. Near the equator, the megathrust is locked over a narrow width of only a few tens of kilometers. In contrast, the locked fault zone is up to about 175 km wide in areas where great interplate earthquakes have occurred in the past. Formal inversion of the data reveals that these strongly coupled patches are roughly coincident with asperities that ruptured during these events. The correlation is most spectacular for rupture of the M_w 8.7 Nias-Simeulue earthquake of 2005, which released half of the moment deficit that had accumulated since its previous rupture in 1861, suggesting that this earthquake was overdue. Beneath the Mentawai islands, strong coupling is observed within the overlapping rupture areas of the great earthquakes of 1797 and 1833. The accumulated slip deficit since these events is slowly reaching the amount of slip that occurred during the 1833 earthquake but already exceeds the slip that occurred during the 1797 earthquake. Thus, rerupture of part of the Mentawai patch in September 2007 was not a surprise. In contrast, coupling is low below the Batu islands near the equator and around Enggano island at about 5\u00b0S, where only moderate earthquakes (M_w < 8.0) have occurred in the past two centuries. The correlation of large seismic asperities with patches that are locked during the interseismic period suggests that they are persistent features. This interpretation is reinforced by the fact that the large locked patches and great ruptures occur beneath persistent geomorphologic features, the largest outer arc islands. Depth- and convergence-rate-dependent temperature might influence the pattern of coupling, through its effect on the rheology of the plate interface, but other influences are required to account for the observed along-strike heterogeneity of coupling. In particular, subduction of the Investigator Fracture Zone could be the cause for the low coupling near the equator.", "doi": "10.1029/2007JB004981", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2008-05-13", "series_number": "B5", "volume": "113", "issue": "B5", "pages": "Art. No. B05305" }, { "id": "authors:rchg4-k3343", "collection": "authors", "collection_id": "rchg4-k3343", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101112-154501489", "type": "article", "title": "Seasonal variations of seismicity and geodetic strain in the Himalaya induced by surface hydrology", "author": [ { "family_name": "Bettinelli", "given_name": "Pierre", "clpid": "Bettinelli-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Flouzat", "given_name": "Mireille", "clpid": "Flouzat-M" }, { "family_name": "Bollinger", "given_name": "Laurent", "clpid": "Bollinger-L" }, { "family_name": "Ramillien", "given_name": "Guillaume", "clpid": "Ramillien-G" }, { "family_name": "Rajaure", "given_name": "Sudhir", "clpid": "Rajaure-S" }, { "family_name": "Sapkota", "given_name": "Som", "clpid": "Sapkota-S" } ], "abstract": "One way to probe earthquake nucleation processes and the relation between stress buildup and seismicity is to analyze the sensitivity of seismicity to stress perturbations. Here, we report evidence for seasonal strain and stress (~ 2\u20134 kPa) variations in the Nepal Himalaya, induced by water storage variations which correlate with seasonal variations of seismicity. The seismicity rate is twice as high in the winter as in the summer, and correlates with stress rate variations. We infer ~ 10\u201320 kPa/yr interseismic stress buildup within the seismicity cluster along the high Himalaya front. Given that Earth tides exert little influence on Himalayan seismicity, the correlated seasonal variation of stress and seismicity indicates that the duration of earthquake nucleation in the Himalaya is of the order of days to month, placing constraints on faults friction laws. The unusual sensitivity of seismicity to small stress changes in the Himalaya might be due to high pore pressure at seismogenic depth.", "doi": "10.1016/j.epsl.2007.11.021", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2008-02-20", "series_number": "3-4", "volume": "266", "issue": "3-4", "pages": "332-344" }, { "id": "authors:kp98e-1kk80", "collection": "authors", "collection_id": "kp98e-1kk80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-092612930", "type": "article", "title": "Monitoring Earth Surface Dynamics With Optical Imagery", "author": [ { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Berthier", "given_name": "Etienne", "clpid": "Berthier-E" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Delacourt", "given_name": "Christophe", "clpid": "Delacourt-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The increasing availability of high-quality optical satellite images should allow, in principle, continuous monitoring of Earth's surface changes due to geologic processes, climate change, or anthropic activity. For instance, sequential optical images have been used to measure displacements at Earth's surface due to coseismic ground deformation [e.g., Van Puymbroeck et al., 2000], ice flow [Scambos et al., 1992; Berthier et al., 2005], sand dune migration [Crippen, 1992], and landslides [K\u00e4\u00e4b, 2002; Delacourt et al., 2004]. Surface changes related to agriculture, deforestation, urbanization, and erosion\u2014which do not involve ground displacement\u2014might also be monitored, provided that the images can be registered with sufficient accuracy. Although the approach is simple in principle, its use is still limited, mainly because of geometric distortion of the images induced by the imaging system, biased correlation techniques, and implementation difficulties.", "doi": "10.1029/2008EO010001", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "2008-01-01", "series_number": "1", "volume": "89", "issue": "1", "pages": "1-2" }, { "id": "authors:hf3gm-hn937", "collection": "authors", "collection_id": "hf3gm-hn937", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-093735810", "type": "article", "title": "Mountain building in Taiwan: A thermokinematic model", "author": [ { "family_name": "Simoes", "given_name": "Martine", "clpid": "Simoes-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Beyssac", "given_name": "Olivier", "clpid": "Beyssac-O" }, { "family_name": "Goff\u00e9", "given_name": "Bruno", "clpid": "Goff\u00e9-B" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" } ], "abstract": "The Taiwan mountain belt is classically viewed as a case example of a critical wedge growing essentially by frontal accretion and therefore submitted to distributed shortening. However, a number of observations call for a significant contribution of underplating to the growth of the orogenic wedge. We propose here a new thermokinematic model of the Taiwan mountain belt reconciling existing kinematic, thermometric and thermochronological constraints. In this model, shortening across the orogen is absorbed by slip on the most frontal faults of the foothills. Crustal thickening and exhumation are sustained by underplating beneath the easternmost portion of the wedge (Tananao Complex, TC), where the uplift rate is estimated to ~6.3 mm a^(\u22121), and beneath the westernmost internal region of the orogen (Hsueshan Range units, HR), where the uplift rate is estimated to ~4.2 mm a^(\u22121). Our model suggests that the TC units experienced a synchronous evolution along strike despite the southward propagation of the collision. It also indicates that they have reached a steady state in terms of cooling ages but not in terms of peak metamorphic temperatures. Exhumation of the HR units increases northward but has not yet reached an exhumational steady state. Presently, frontal accretion accounts for less than ~10% of the incoming flux of material into the orogen, although there is indication that it was contributing substantially more (~80%) before 4 Ma. The incoming flux of material accreted beneath the TC significantly increased 1.5 Ma ago. Our results also suggest that the flux of material accreted to the orogen corresponds to the top ~7 km of the upper crust of the underthrust Chinese margin. This indicates that a significant amount (~76%) of the underthrust material has been subducted into the mantle, probably because of the increase in density associated with metamorphism. We also show that the density distribution resulting from metamorphism within the orogenic wedge explains well the topography and the gravity field. By combining available geological data on the thermal and kinematic evolution of the wedge, our study sheds new light onto mountain building processes in Taiwan and allows for reappraising the initial structural architecture of the passive margin.", "doi": "10.1029/2006JB004824", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-11-28", "series_number": "B11", "volume": "112", "issue": "B11", "pages": "Art. No. B11405" }, { "id": "authors:ynfy2-y8q51", "collection": "authors", "collection_id": "ynfy2-y8q51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-095303150", "type": "article", "title": "Late Cenozoic metamorphic evolution and exhumation of Taiwan", "author": [ { "family_name": "Beyssac", "given_name": "Olivier", "clpid": "Beyssac-O" }, { "family_name": "Simoes", "given_name": "Martine", "clpid": "Simoes-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" }, { "family_name": "Chan", "given_name": "Yu-Chang", "clpid": "Chan-Yu-Chang" }, { "family_name": "Goff\u00e9", "given_name": "Bruno", "clpid": "Goff\u00e9-B" } ], "abstract": "The Taiwan mountain belt is composed of a Cenozoic slate belt (Hsuehshan Range units, HR, and Backbone Slates, BS) and of accreted polymetamorphic basement rocks (Tananao Complex, TC). Ongoing crustal shortening has resulted from the collision between the Chinese continental margin and the Luzon volcanic arc, which initiated ~6.5 Ma ago. The grade and age of metamorphism and exhumation are a key record of the development of the orogenic wedge. Because the Taiwan mountain belt is mostly composed by accreted sediments lacking metamorphic index minerals, quantitative constraints on metamorphism are sparse. By contrast, these rocks are rich in carbonaceaous material (CM) and are therefore particularly appropriate for RSCM (Raman Spectroscopy of CM) thermometry. We apply this technique in addition to (U-Th)/He thermochronology on detrital zircons to assess peak metamorphic temperatures (T) and the late exhumational history respectively, along different transects in central and southern Taiwan. In the case of the HR units, we find evidence for high metamorphic T of at least 340\u00b0\u2013350\u00b0C and locally up to 475\u00b0C, and for relative rapid exhumation with zircon (U-Th)/He ages in the range of 1.5\u20132 Ma. Farther east, the BS were only slightly metamorphosed (T < 330 \u00b0C), and zircons are not reset for (U-Th)/He. From the eastern BS to the inner TC schists, T gradually increases from ~350\u00b0C up to ~500\u00b0C following an inverted metamorphic gradient. Available geochronological constraints and the continuous thermal gradient from the BS to the basement rocks of the TC suggest that the high RSCM T of the TC were most probably acquired during the last orogeny, and were not inherited from a previous thermal event. Zircons yield (U-Th)/He ages of ~0.5\u20131.2 Ma. Peak metamorphic T and the timing of exhumation do not show along-strike variations over the TC in the studied area. In contrast, exhumation is laterally diachronous and decreases southward in the case of the HR units. In particular, our data imply that the HR units have been exhumed by a minimum of 15 km over the last few Ma. In the case of the BS, they show far less cumulated exhumation and much slower cooling rates. We propose that most of the deformation and exhumation of the Taiwan mountain belt is sustained through two underplating windows located beneath the Hsuehshan Range and the TC. Our data show significant departures from the predictions of the prevailing model in Taiwan, which assumes a homogeneous critical wedge with dominant frontal accretion. Our study sheds new light on how the mountain belt has grown as a possible result of underplating mostly.", "doi": "10.1029/2006TC002064", "issn": "0278-7407", "publisher": "American Geophysical Union", "publication": "Tectonics", "publication_date": "2007-11-07", "series_number": "6", "volume": "26", "issue": "6", "pages": "Art. No. TC6001" }, { "id": "authors:x0gyj-2sa90", "collection": "authors", "collection_id": "x0gyj-2sa90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-101204985", "type": "article", "title": "Seismic tomography of Taiwan: Improved constraints from a dense network of strong motion stations", "author": [ { "family_name": "Wu", "given_name": "Yih-Min", "clpid": "Wu-Yih-Min" }, { "family_name": "Chang", "given_name": "Chien-Hsin", "clpid": "Chang-Chien-Hsin" }, { "family_name": "Zhao", "given_name": "Li", "clpid": "Zhao-Li" }, { "family_name": "Shyu", "given_name": "J. Bruce H.", "orcid": "0000-0002-2564-3702", "clpid": "Shyu-J-Bruce-H" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "In this study, a large collection of 41,141 S-P times from the untapped records of the Taiwan Strong Motion Instrumentation Program (TSMIP) network is combined with the P and S wave arrival times from the Taiwan Central Weather Bureau Seismic Network (CWBSN) to image the V_p and V_p /V_s structures beneath Taiwan. The records from the 680 TSMIP stations throughout Taiwan in the past 15 years enhance the path coverage and the resolution in the tomography inversions tremendously. Our result for the V_p structure largely confirms previous studies but brings better constraint on the V_p /V_s structure. The colliding Luzon volcanic arc is characterized by a belt of high V_p and high V_p /V_s with high seismicity that includes the offshore islands of Lutao and Lanyu and the Coastal Ranges in eastern Taiwan, at the depth between about 13 and 25 km. This high V_p /V_s belt can be traced to the subduction zone in the region between Hualian and Ilan in the deeper portion. The shallow portions of the southwestern coastal plain and the Pingtung region are also characterized by a belt of high V_p /V_s with lower seismicity. Most of the events occurred at the base of the high V_p /V_s zones. We suggest that material strength in those regions may be too low to accumulate stress, which may indicate water-saturated young sediments. Finally, the Central Range region is characterized by a low V_p /V_s belt.", "doi": "10.1029/2007JB004983", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-08-23", "series_number": "B8", "volume": "112", "issue": "B8", "pages": "Art. No. B08312" }, { "id": "authors:3kn97-gxa42", "collection": "authors", "collection_id": "3kn97-gxa42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-104352655", "type": "article", "title": "Modeling afterslip and aftershocks following the 1992 Landers earthquake", "author": [ { "family_name": "Perfettini", "given_name": "H.", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "One way to probe the rheology of the lithosphere and fault zones is to analyze the temporal evolution of deformation following a large earthquake. In such a case, the lithosphere responds to a known stress change that can be assessed from earthquake slip models constrained from seismology and geodesy. Here, we model the postseismic response of a fault zone that is assumed to obey a rate-strengthening rheology, where the frictional stress varies as a\u03c3 ln(\u03b5), \u03b5 being the deformation rate and a\u03c3 > 0 a rheological parameter. The model is simple enough that these parameters can be estimated by inversion of postseismic geodetic data. We apply this approach to the analysis of geodetic displacements following the M_w 7.3, 1992, Landers earthquake. The model adjusts well the measured displacements and implies a\u03c3 \u2248 0.47\u20130.53 MPa. In addition, we show that aftershocks and afterslip follow the same temporal evolution and that the spatiotemporal distribution of aftershocks is consistent with the idea that they are driven by reloading of the seismogenic zone resulting from frictional afterslip.", "doi": "10.1029/2006JB004399", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-07-19", "series_number": "B7", "volume": "112", "issue": "B7", "pages": "Art. No. B07409" }, { "id": "authors:11fjc-7y118", "collection": "authors", "collection_id": "11fjc-7y118", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LEPieeetgrs07", "type": "article", "title": "Automatic and Precise Orthorectification, Coregistration, and Subpixel Correlation of Satellite Images, Application to Ground Deformation Measurements", "author": [ { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Barbot", "given_name": "Sylvain", "orcid": "0000-0003-4257-7409", "clpid": "Barbot-S" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We describe a procedure to accurately measure ground deformations from optical satellite images. Precise orthorectification is obtained owing to an optimized model of the imaging system, where look directions are linearly corrected to compensate for attitude drifts, and sensor orientation uncertainties are accounted for. We introduce a new computation of the inverse projection matrices for which a rigorous resampling is proposed. The irregular resampling problem is explicitly addressed to avoid introducing aliasing in the ortho-rectified images. Image registration and correlation is achieved with a new iterative unbiased processor that estimates the phase plane in the Fourier domain for subpixel shift detection. Without using supplementary data, raw images are wrapped onto the digital elevation model and coregistered with a 1/50 pixel accuracy. The procedure applies to images from any pushbroom imaging system. We analyze its performance using Satellite pour l'Observation de la Terre (SPOT) images in the case of a null test (no coseismic deformation) and in the case of large coseismic deformations due to the Mw 7.1 Hector Mine, California, earthquake of 1999. The proposed technique would also allow precise coregistration of images for the measurement of surface displacements due to ice-flow or geomorphic processes, or for any other change detection applications. A complete software package, the Coregistration of Optically Sensed Images and Correlation, is available for download from the Caltech Tectonics Observatory website.", "doi": "10.1109/TGRS.2006.888937", "issn": "0196-2892", "publisher": "IEEE Transactions on Geoscience and Remote Sensing", "publication": "IEEE Transactions on Geoscience and Remote Sensing", "publication_date": "2007-06", "series_number": "6", "volume": "45", "issue": "6", "pages": "1529-1558" }, { "id": "authors:t9t1f-xzs54", "collection": "authors", "collection_id": "t9t1f-xzs54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-105624515", "type": "article", "title": "Tropospheric phase delay in interferometric synthetic aperture radar estimated from meteorological model and multispectral imagery", "author": [ { "family_name": "Puyss\u00e9gur", "given_name": "B\u00e9atrice", "clpid": "Puyss\u00e9gur-B" }, { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "ENVISAT Medium Resolution Imaging Spectrometer Instrument (MERIS) multispectral data and the mesoscale meteorological model MM5 are used to estimate the tropospheric phase delay in synthetic aperture radar (SAR) interferograms. MERIS images acquired simultaneously with ENVISAT Advanced Synthetic Aperture Radar data provide an estimate of the total water vapor content W limited to cloud-free areas based on spectral bands ratio (accuracy 0.17 g cm^(\u22122) and ground resolution 300 m). Maps of atmospheric delay, 2 km in ground resolution, are simulated from MM5. A priori pertinent cumulus parameterization and planetary boundary layer options of MM5 yield near-equal phase correction efficiency. Atmospheric delay derived from MM5 is merged with available MERIS W product. Estimates of W measured from MERIS and modeled from MM5 are shown to be consistent and unbiased and differ by ~0.2 g cm^(\u22122) (RMS). We test the approach on data over the Lebanese ranges where active tectonics might contribute to a measurable SAR signal that is obscured by atmospheric effects. Local low-amplitude (1 rad) atmospheric oscillations with a 2.25 km wavelength on the interferograms are recovered from MERIS with an accuracy of 0.44 rad or 0.03 g cm^(\u22122). MERIS water product overestimates W in the clouds shadow due to mismodeling of multiple scattering and underestimates W on pixels with undetected semitransparent clouds. The proposed atmospheric filter models dynamic atmospheric signal which cannot be recovered by previous filtering techniques which are based on a static atmospheric correction. Analysis of filter efficiency with spatial wavelength shows that ~43% of the atmospheric signal is removed at all wavelengths.", "doi": "10.1029/2006JB004352", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-05-30", "series_number": "5", "volume": "112", "issue": "5", "pages": "Art. No. B05419" }, { "id": "authors:xrn40-1vn87", "collection": "authors", "collection_id": "xrn40-1vn87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-115352564", "type": "article", "title": "Seasonal modulation of seismicity in the Himalaya of Nepal", "author": [ { "family_name": "Bollinger", "given_name": "L.", "clpid": "Bollinger-L" }, { "family_name": "Perrier", "given_name": "F.", "clpid": "Perrier-F" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sapkota", "given_name": "S.", "clpid": "Sapkota-S" }, { "family_name": "Gautam", "given_name": "U.", "clpid": "Gautam-U" }, { "family_name": "Tiwari", "given_name": "D. R.", "clpid": "Tiwari-D-R" } ], "abstract": "For the period 1995\u20132000, the Nepal seismic network recorded 37 \u00b1 8% fewer earthquakes in the summer than in the winter; for local magnitudes ML > 2 to ML > 4 the percentage increases from 31% to 63% respectively. We show the probability of observing this by chance is less than 1%. We find that most surface loading phenomena are either too small, or have the wrong polarity to enhance winter seismicity. We consider enhanced Coulomb failure caused by a pore-pressure increase at seismogenic depths as a possible mechanism. For this to enhance winter seismicity, however, we find that fluid diffusion following surface hydraulic loading would need to be associated with a six-month phase lag, which we consider to be possible, though unlikely. We favor instead the suppression of summer seismicity caused by stress-loading accompanying monsoon rains in the Ganges and northern India, a mechanism that is discussed in a companion article.", "doi": "10.1029/2006GL029192", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2007-04-26", "series_number": "8", "volume": "34", "issue": "8", "pages": "Art. No. L08304" }, { "id": "authors:wr02g-fw467", "collection": "authors", "collection_id": "wr02g-fw467", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120906-103503110", "type": "article", "title": "Introduction to special section: Active Fault-Related Folding: Structural Evolution, Geomorphologic Expression, Paleoseismology, and Seismic Hazards", "author": [ { "family_name": "Dolan", "given_name": "James F.", "clpid": "Dolan-J-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "N/A", "doi": "10.1029/2007JB004952", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-03-28", "series_number": "B3", "volume": "112", "issue": "B3", "pages": "Art. No. B03S01" }, { "id": "authors:2vjyn-ykd06", "collection": "authors", "collection_id": "2vjyn-ykd06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-123245277", "type": "article", "title": "Modeling the shortening history of a fault tip fold using structural and geomorphic records of deformation", "author": [ { "family_name": "Da\u00ebron", "given_name": "Mathieu", "clpid": "Da\u00ebron-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" } ], "abstract": "We present a methodology to derive the growth history of a fault tip fold above a basal detachment. Our approach is based on modeling the stratigraphic and geomorphic records of deformation, as well as the finite structure of the fold constrained from seismic profiles. We parameterize the spatial deformation pattern using a simple formulation of the displacement field derived from sandbox experiments. Assuming a stationary spatial pattern of deformation, we simulate the gradual warping and uplift of stratigraphic and geomorphic markers, which provides an estimate of the cumulative amounts of shortening they have recorded. This approach allows modeling of isolated terraces or growth strata. We apply this method to the study of two fault tip folds in the Tien Shan, the Yakeng and Anjihai anticlines, documenting their deformation history over the past 6\u20137 Myr. We show that the modern shortening rates can be estimated from the width of the fold topography provided that the sedimentation rate is known, yielding respective rates of 2.15 and 1.12 mm/yr across Yakeng and Anjihai, consistent with the deformation recorded by fluvial and alluvial terraces. This study demonstrates that the shortening rates across both folds accelerated significantly since the onset of folding. It also illustrates the usefulness of a simple geometric folding model and highlights the importance of considering local interactions between tectonic deformation, sedimentation, and erosion.", "doi": "10.1029/2006JB004460", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-03-10", "series_number": "B3", "volume": "112", "issue": "B3", "pages": "Art. No. B03S13" }, { "id": "authors:zwn0d-3vq07", "collection": "authors", "collection_id": "zwn0d-3vq07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101115-153513150", "type": "article", "title": "Kinematics of fault-related folding derived from a sandbox experiment", "author": [ { "family_name": "Bernard", "given_name": "Sylvain", "clpid": "Bernard-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Simoes", "given_name": "Martine", "clpid": "Simoes-M" } ], "abstract": "We analyze the kinematics of fault tip folding at the front of a fold-and-thrust wedge using a sandbox experiment. The analog model consists of sand layers intercalated with low-friction glass bead layers, deposited in a glass-sided experimental device and with a total thickness h = 4.8 cm. A computerized mobile backstop induces progressive horizontal shortening of the sand layers and therefore thrust fault propagation. Active deformation at the tip of the forward propagating basal d\u00e9collement is monitored along the cross section with a high-resolution CCD camera, and the displacement field between pairs of images is measured from the optical flow technique. In the early stage, when cumulative shortening is less than about h/10, slip along the d\u00e9collement tapers gradually to zero and the displacement gradient is absorbed by distributed deformation of the overlying medium. In this stage of detachment tip folding, horizontal displacements decrease linearly with distance toward the foreland. Vertical displacements reflect a nearly symmetrical mode of folding, with displacements varying linearly between relatively well defined axial surfaces. When the cumulative slip on the d\u00e9collement exceeds about h/10, deformation tends to localize on a few discrete shear bands at the front of the system, until shortening exceeds h/8 and deformation gets fully localized on a single emergent frontal ramp. The fault geometry subsequently evolves to a sigmoid shape and the hanging wall deforms by simple shear as it overthrusts the flat ramp system. As long as strain localization is not fully established, the sand layers experience a combination of thickening and horizontal shortening, which induces gradual limb rotation. The observed kinematics can be reduced to simple analytical expressions that can be used to restore fault tip folds, relate finite deformation to incremental folding, and derive shortening rates from deformed geomorphic markers or growth strata.", "doi": "10.1029/2005JB004149", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-02-17", "series_number": "B3", "volume": "112", "issue": "B3", "pages": "Art. No. B03S12" }, { "id": "authors:gb7x4-z5s98", "collection": "authors", "collection_id": "gb7x4-z5s98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101116-080307482", "type": "article", "title": "Kinematic analysis of the Pakuashan fault tip fold, west central Taiwan: Shortening rate and age of folding inception", "author": [ { "family_name": "Simoes", "given_name": "Martine", "clpid": "Simoes-M" }, { "family_name": "Avouac", "given_name": "Jean Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" }, { "family_name": "Singhvi", "given_name": "Ashok K.", "clpid": "Singhvi-A-K" }, { "family_name": "Wang", "given_name": "Chien-Ying", "clpid": "Wang-Chien-Ying" }, { "family_name": "Jaiswal", "given_name": "Manoj", "clpid": "Jaiswal-M-K" }, { "family_name": "Chan", "given_name": "Yu-Chang", "clpid": "Chan-Yu-Chang" }, { "family_name": "Bernard", "given_name": "Sylvain", "clpid": "Bernard-S" } ], "abstract": "The Pakuashan anticline is an active fault tip fold that constitutes the frontal most zone of deformation along the western piedmont of the Taiwan Range. Assessing seismic hazards associated with this fold and its contribution to crustal shortening across central Taiwan requires some understanding of the fold structure and growth rate. To address this, we surveyed the geometry of several deformed strata and geomorphic surfaces, which recorded different cumulative amounts of shortening. These units were dated to ages ranging from ~19 ka to ~340 ka using optically stimulated luminescence (OSL). We collected shallow seismic profiles and used previously published seismic profiles to constrain the deep structure of the fold. These data show that the anticline has formed as a result of pure shear with subsequent limb rotation. The cumulative shortening along the direction of tectonic transport is estimated to be 1010 \u00b1 160 m. An analytical fold model derived from a sandbox experiment is used to model growth strata. This yields a shortening rate of 16.3 \u00b1 4.1 mm/yr and constrains the time of initiation of deformation to 62.2 \u00b1 9.6 ka. In addition, the kinematic model of Pakuashan is used to assess how uplift, sedimentation, and erosion have sculpted the present-day fold topography and morphology. The fold model, applied here for the first time on a natural example, appears promising in determining the kinematics of fault tip folds in similar contexts and therefore in assessing seismic hazards associated with blind thrust faults.", "doi": "10.1029/2005JB004198", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-02-13", "series_number": "B3", "volume": "112", "issue": "B3", "pages": "Art. No. B03S14" }, { "id": "authors:chrbx-z5059", "collection": "authors", "collection_id": "chrbx-z5059", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101116-080938475", "type": "article", "title": "Slip rates on the Chelungpu and Chushiang thrust faults inferred from a deformed strath terrace along the Dungpuna river, west central Taiwan", "author": [ { "family_name": "Simoes", "given_name": "Martine", "clpid": "Simoes-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" } ], "abstract": "The Chelungpu fault produced the September 1999 M_w = 7.6 Chi-Chi earthquake, central Taiwan. The shortening rate accommodated by this structure, integrated over several seismic cycles, and its contribution to crustal shortening across the Taiwanese range have remained unresolved. To address the issues, we focus our study on the Chelungpu and Chushiang thrust faults within the southernmost portion of the Chi-Chi rupture area. Structural measurements and available seismic profiles are used to infer the subsurface geometry of structures. The Chushiang and Chelungpu faults appear as two splay faults branching onto a common ramp that further north connects only to the Chelungpu surface trace. We survey a deformed strath terrace along the Dungpuna river, buried under a 11,540 \u00b1 309 years old fill deposit. Given this age, the dip angles of the faults, and the vertical throw determined from the offset of the strath terrace across the surface fault traces, we estimate slip rates of 12.9 \u00b1 4.8 and 2.9 \u00b1 1.6 mm/yr on the Chelungpu and Chushiang faults, respectively. These yield a total shortening rate of 15.8 \u00b1 5.1 mm/yr to be absorbed on their common decollement at depth. This total value is an upper bound for the slip rate on the Chelungpu fault further north, where the Chushiang fault disappears and transfers shortening to adjacent faults. Combining these results with the recently constrained shortening rate on the Changhua blind thrust reveals that all these frontal faults presently absorb most of the long-term horizontal shortening across the Taiwanese range. They thus stand as the major sources of seismic hazards in this heavily populated area. The return period of earthquakes similar to the Chi-Chi event over a \u223c80 km long stretch of the Western Foothills is estimated to be ~64 years. This value is an underestimate because it assumes that all the faults locked during the interseismic period slip only during such large events. Comparison with historical seismicity suggests that episodic aseismic deformation might also play a major role in accommodating shortening.", "doi": "10.1029/2005JB004200", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2007-02-09", "series_number": "B3", "volume": "112", "issue": "B3", "pages": "Art. No. B03S10" }, { "id": "authors:8fssm-tj410", "collection": "authors", "collection_id": "8fssm-tj410", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101116-092441405", "type": "article", "title": "Rupture Kinematics of the 2005 M_w 8.6 Nias\u2013Simeulue Earthquake from the Joint Inversion of Seismic and Geodetic Data", "author": [ { "family_name": "Konca", "given_name": "A. Ozgun", "clpid": "Konca-A-Ozgun" }, { "family_name": "Hjorleifsdottir", "given_name": "Vala", "orcid": "0000-0003-3275-108X", "clpid": "Hjorleifsdottir-Vala" }, { "family_name": "Song", "given_name": "Teh-Ru Alex", "orcid": "0000-0003-3697-5881", "clpid": "Song-Teh-Ru-Alex" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Helmberger", "given_name": "Don V.", "clpid": "Helmberger-D-V" }, { "family_name": "Ji", "given_name": "Chen", "orcid": "0000-0002-0350-5704", "clpid": "Ji-Chen" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Briggs", "given_name": "Richard", "clpid": "Briggs-R-W" }, { "family_name": "Meltzner", "given_name": "Aron", "orcid": "0000-0002-2955-0896", "clpid": "Meltzner-A-J" } ], "abstract": "The 2005 M_w 8.6 Nias\u2013Simeulue earthquake was caused by rupture of a portion of the Sunda megathrust offshore northern Sumatra. This event occurred within an array of continuous Global Positioning System (GPS) stations and produced measurable vertical displacement of the fringing coral reefs above the fault rupture. Thus, this earthquake provides a unique opportunity to assess the source characteristics of a megathrust event from the joint analysis of seismic data and near-field static co-seismic displacements. Based on the excitation of the normal mode data and geodetic data we put relatively tight constraints on the seismic moment and the fault dip, where the dip is determined to be 8\u00b0 to 10\u00b0 with corresponding moments of 1.24 x 10^(22) to 1.00 x 10^(22) N m, respectively. The geodetic constraints on slip distribution help to eliminate the trade-off between rupture velocity and slip kinematics. Source models obtained from the inversion of various combinations of the teleseismic body waves and geodetic data are evaluated by comparing predicted and observed long-period seismic waveforms (100\u2013500 sec). Our results indicate a relatively slow average rupture velocity of 1.5 to 2.5 km/sec and long average rise time of up to 20 sec. The earthquake nucleated between two separate slip patches, one beneath Nias and the other beneath Simeulue Island. The gap between the two patches and the hypocentral location appears to be coincident with a local geological disruption of the forearc. Coseismic slip clearly tapers to zero before it reaches the trench probably because the rupture propagation was inhibited when it reached the accretionary prism. Using the models from joint inversions, we estimate the peak ground velocity on Nias Island to be about 30 cm/sec, an order of magnitude slower than for thrust events in continental areas. This study emphasizes the importance of utilizing multiple datasets in imaging seismic ruptures.", "doi": "10.1785/0120050632", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2007-01", "series_number": "1", "volume": "97", "issue": "1", "pages": "S307-S322" }, { "id": "authors:g976w-hvb70", "collection": "authors", "collection_id": "g976w-hvb70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101116-091058235", "type": "article", "title": "Coseismic Slip and Afterslip of the Great M_w 9.15 Sumatra\u2013Andaman Earthquake of 2004", "author": [ { "family_name": "Chlieh", "given_name": "Mohamed", "clpid": "Chlieh-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hjorleifsdottir", "given_name": "Vala", "orcid": "0000-0003-3275-108X", "clpid": "Hjorleifsdottir-Vala" }, { "family_name": "Song", "given_name": "Teh-Ru Alex", "orcid": "0000-0003-3697-5881", "clpid": "Song-Teh-Ru-Alex" }, { "family_name": "Ji", "given_name": "Chen", "orcid": "0000-0002-0350-5704", "clpid": "Ji-Chen" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Sladen", "given_name": "Anthony", "orcid": "0000-0003-4126-0020", "clpid": "Sladen-A" }, { "family_name": "Hebert", "given_name": "Helene", "clpid": "Hebert-Helene" }, { "family_name": "Prawirodirdjo", "given_name": "Linette", "clpid": "Prawirodirdjo-L" }, { "family_name": "Bock", "given_name": "Yehuda", "clpid": "Bock-Y" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" } ], "abstract": "We determine coseismic and the first-month postseismic deformation associated with the Sumatra\u2013Andaman earthquake of 26 December 2004 from near- field Global Positioning System (GPS) surveys in northwestern Sumatra and along the Nicobar-Andaman islands, continuous and campaign GPS measurements from Thailand and Malaysia, and in situ and remotely sensed observations of the vertical motion of coral reefs. The coseismic model shows that the Sunda subduction megathrust ruptured over a distance of about 1500 km and a width of less than 150 km, releasing a total moment of 6.7\u20137.0 x 10^(22) N m, equivalent to a magnitude M_w 9.15. The latitudinal distribution of released moment in our model has three distinct peaks at about 4\u00b0 N, 7\u00b0 N, and 9\u00b0 N, which compares well to the latitudinal variations seen in the seismic inversion and of the analysis of radiated T waves. Our coseismic model is also consistent with interpretation of normal modes and with the amplitude of very-long-period surface waves. The tsunami predicted from this model fits relatively well the altimetric measurements made by the JASON and TOPEX satellites. Neither slow nor delayed slip is needed to explain the normal modes and the tsunami wave. The near-field geodetic data that encompass both coseismic deformation and up to 40 days of postseismic deformation require that slip must have continued on the plate interface after the 500-sec-long seismic rupture. The postseismic geodetic moment of about 2.4 x 10^(22) N m (M_w 8.8) is equal to about 30 \u00b1 5% of the coseismic moment release. Evolution of postseismic deformation is consistent with rate-strengthening frictional afterslip.", "doi": "10.1785/0120050631", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2007-01", "series_number": "1", "volume": "97", "issue": "1", "pages": "S152-S173" }, { "id": "authors:np274-vk180", "collection": "authors", "collection_id": "np274-vk180", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-134557761", "type": "article", "title": "Plate Motion of India and Interseismic Strain in the Nepal Himalaya from GPS and DORIS Measurements", "author": [ { "family_name": "Bettinelli", "given_name": "Pierre", "clpid": "Bettinelli-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Flouzat", "given_name": "Mireille", "clpid": "Flouzat-M" }, { "family_name": "Jouanne", "given_name": "Fran\u00e7ois", "clpid": "Jouanne-F" }, { "family_name": "Bollinger", "given_name": "Laurent", "clpid": "Bollinger-L" }, { "family_name": "Willis", "given_name": "Pascal", "clpid": "Willis-P" }, { "family_name": "Chitrakar", "given_name": "Gyani Raja", "clpid": "Chitrakar-G-R" } ], "abstract": "We analyse geodetically estimated deformation\nacross the Nepal Himalaya in order to determine the geodetic\nrate of shortening between Southern Tibet and India,\npreviously proposed to range from 12 to 21 mm yr^(\u22121). The\ndataset includes spirit-levelling data along a road going from\nthe Indian to the Tibetan border across Central Nepal, data\nfrom the DORIS station on Everest, which has been analysed\nsince 1993, GPS campaign measurements from surveys\ncarried on between 1995 and 2001, as well as data from continuous\nGPS stations along a transect at the logitude of Kathmandu\noperated continuously since 1997. The GPS data were processed in International Terrestrial Reference Frame 2000\n(ITRF2000), together with the data from 20 International\nGNSS Service (IGS) stations and then combined using quasi observation\ncombination analysis (QOCA). Finally, spatially\ncomplementary velocities at stations in Southern Tibet, initially\ndetermined in ITRF97, were expressed in ITRF2000.\nAfter analysing previous studies by different authors, we\ndetermined the pole of rotation of the Indian tectonic plate to\nbe located in ITRF2000 at 51.409\u00b11.560\u00b0N and\u221210.915\u00b1\n5.556\u00b0E, with an angular velocity of 0.483\u00b10.015\u00b0. Myr^(\u22121).\nInternal deformation of India is found to be small, corresponding\nto less than about 2 mm yr^(\u22121) of baseline change\nbetween Southern India and the Himalayan piedmont. Based\non an elastic dislocation model of interseismic strain and\ntaking into account the uncertainty on India plate motion,\nthe mean convergence rate across Central and Eastern Nepal\nis estimated to 19 \u00b1 2.5 mm yr^(\u22121), (at the 67% confidence\nlevel). The main himalayan thrust (MHT) fault was found to\nbe locked from the surface to a depth of about 20km over a\nwidth of about 115 km. In these regions, the model parameters\nare well constrained, thanks to the long and continuous\ntime-series from the permanent GPS as well as DORIS data.\nFurther west, a convergence rate of 13.4 \u00b1 5 mm yr^(\u22121), as\nwell as a fault zone, locked over 150 km, are proposed. The\nslight discrepancy between the geologically estimated deformation\nrate of 21 \u00b1 1.5 mm yr^(\u22121) and the 19 \u00b1 2.5 mm yr^(\u22121)\ngeodetic rate in Central and Eastern Nepal, as well as the\nlower geodetic rate in Western Nepal compared to Eastern\nNepal, places bounds on possible temporal variations of the\npattern and rate of strain in the period between large earthquakes\nin this region.", "doi": "10.1007/s00190-006-0030-3", "issn": "0949-7714", "publisher": "Springer Verlag", "publication": "Journal of Geodesy", "publication_date": "2006-11", "series_number": "8-11", "volume": "80", "issue": "8-11", "pages": "567-589" }, { "id": "authors:2m78d-dje49", "collection": "authors", "collection_id": "2m78d-dje49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101116-110335366", "type": "article", "title": "Investigating the kinematics of mountain building in Taiwan from the spatiotemporal evolution of the foreland basin and western foothills", "author": [ { "family_name": "Simoes", "given_name": "Martine", "clpid": "Simoes-M" }, { "family_name": "Avouac", "given_name": "Jean Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The Taiwanese range has resulted from the collision between the Luzon volcanic arc and the Chinese continental margin, which started about 6.5 Myr ago in the north, and has since propagated southward. The building of the range has been recorded in the spatiotemporal evolution of the foreland basin. We analyze this sedimentary record to place some constraints on the kinematics of crustal deformation. The flexure of the foreland under the load of the growing wedge started with a 1.5 Myr long phase of rapid subsidence and sedimentation, which has migrated southward over the last 3.5 Myr at a rate of 31 +10/\u22125 mm/yr, reflecting the structural evolution of the range and the growth of the topography during the oblique collision. Isopachs from the Toukoshan (~0 to 1.1 Ma) and Cholan (~1.1 to 3.3 Ma) formations, as well as the sedimentation rates retrieved from a well on the Pakuashan anticline, indicate that the foreland basement has been moving toward the center of mass of the orogen by ~45\u201350 mm/yr during the development of the basin. From there, we estimate the long-term shortening rate across the range to 39.5\u201344.5 mm/yr. By considering available data on the thrust faults of the foothills of central Taiwan, we show that most (if not all) the shortening across the range is accommodated by the most frontal structures, with little if any internal shortening within the wedge. The range growth appears therefore to have been essentially sustained by underplating rather than by frontal accretion. In addition, only the upper ~7 to 9 km of the underthrusted crust participates to the growth of the orogen. This requires that a significant amount of the Chinese passive margin crust is subducted beneath the Philippine Sea plate.", "doi": "10.1029/2005JB004209", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2006-10-05", "series_number": "B10", "volume": "111", "issue": "B10", "pages": "Art. No. B10401" }, { "id": "authors:sxvc2-ca149", "collection": "authors", "collection_id": "sxvc2-ca149", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101116-151107763", "type": "article", "title": "The 2005, M_w 7.6 Kashmir earthquake: Sub-pixel correlation of ASTER images and seismic waveforms analysis", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ayoub", "given_name": "Fran\u00e7ois", "orcid": "0000-0002-7389-8400", "clpid": "Ayoub-F" }, { "family_name": "Leprince", "given_name": "S\u00e9bastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Konca", "given_name": "Ozgun", "clpid": "Konca-O" }, { "family_name": "Helmberger", "given_name": "Don V.", "clpid": "Helmberger-D-V" } ], "abstract": "We analyze the M_w 7.6 Kashmir earthquake of October 8, 2005, using sub-pixel correlation of ASTER images to measure ground deformation, and modeling seismic waveforms. The surface rupture is continuous over a distance of 75 km and cuts across the Hazara syntaxis reactivating the Tanda and the Muzaffarabad faults. North of Muzaffarabad the surface rupture coincides approximately with the MBT, on the southwestern flank of the syntaxis, although the two faults have opposite dip angles. The rupture terminates abruptly at the hairpin turn of the MBT showing a strong structural control. The fault offset is 4 m on average and peaks to 7 m northwest of Muzaffarabad. The rupture lasted about 25 s and propagated updip and bi-laterally ~2 km/s, with a rise time of 2\u20135 s. The shallowness and compactness of the rupture, both in time and space, provide an explanation for the intensity of destructions. This kind of analysis could be achieved as soon as a post-earthquake image is available, and would provide key information for early assessment of damages. The study sheds some light on seismic hazard in the Himalaya, and raises concern regarding the possibility of a repetition of the 1555 event which presumably ruptured the Himalayan front south of the Kashmir basin and may have reached a magnitude M_w > 8.", "doi": "10.1016/j.epsl.2006.06.025", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2006-09-30", "series_number": "3-4", "volume": "249", "issue": "3-4", "pages": "514-528" }, { "id": "authors:03hw8-x6m26", "collection": "authors", "collection_id": "03hw8-x6m26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101116-152223235", "type": "article", "title": "Millennial slip rate of the Longitudinal Valley fault from river terraces: Implications for convergence across the active suture of eastern Taiwan", "author": [ { "family_name": "Shyu", "given_name": "J. Bruce H.", "orcid": "0000-0002-2564-3702", "clpid": "Shyu-J-Bruce-H" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chen", "given_name": "Wen-Shan", "clpid": "Chen-Wen-Shan" }, { "family_name": "Chen", "given_name": "Yue-Gau", "orcid": "0000-0002-8693-583X", "clpid": "Chen-Yue-Gau" } ], "abstract": "The Longitudinal Valley fault is a key element in the active tectonics of Taiwan. It is the principal structure accommodating convergence across one of the two active sutures of the Taiwan orogeny. To understand more precisely its role in the suturing process, we analyzed fluvial terraces along the Hsiukuluan River, which cuts across the Coastal Range in eastern Taiwan in the fault's hanging wall block. This allowed us to determine both its subsurface geometry and its long-term slip rate. The uplift pattern of the terraces is consistent with a fault-bend fold model. Our analysis yields a listric geometry, with dips decreasing downdip from about 50\u00b0 to about 30\u00b0 in the shallowest 2.5 km. The Holocene rate of dip slip of the fault is about 22.7 mm/yr. This rate is less than the 40 mm/yr rate of shortening across the Longitudinal Valley derived from GPS measurements. The discrepancy may reflect an actual difference in millennial and decadal rates of convergence. An alternative explanation is that the discrepancy is accommodated by a combination of slip on the Central Range fault and subsidence of the Longitudinal Valley floor. The shallow, listric geometry of the Longitudinal Valley fault at the Hsiukuluan River valley differs markedly from the deep listric geometry illuminated by earthquake hypocenters near Chihshang, 45 km to the south. We hypothesize that this fundamental along-strike difference in geometry of the fault is a manifestation of the northward maturation of the suturing of the Luzon volcanic arc to the Central Range continental sliver.", "doi": "10.1029/2005JB003971", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2006-08-12", "series_number": "B8", "volume": "111", "issue": "B8", "pages": "Art. No. B08403" }, { "id": "authors:ep2c3-gfw44", "collection": "authors", "collection_id": "ep2c3-gfw44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-080409426", "type": "article", "title": "Frictional Afterslip Following the 2005 Nias-Simeulue Earthquake, Sumatra", "author": [ { "family_name": "Hsu", "given_name": "Ya-Ju", "clpid": "Hsu-Ya-Ju" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Chlieh", "given_name": "Mohamed", "clpid": "Chlieh-M" }, { "family_name": "Natawidjaja", "given_name": "Danny", "clpid": "Natawidjaja-D-H" }, { "family_name": "Prawirodirdjo", "given_name": "Linette", "clpid": "Prawirodirdjo-L" }, { "family_name": "Bock", "given_name": "Yehuda", "clpid": "Bock-Y" } ], "abstract": "Continuously recording Global Positioning System stations near the 28 March 2005 rupture of the Sunda megathrust [moment magnitude (M_w) 8.7] show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust, with a major fraction of this slip in the up-dip direction from the main rupture. Eleven months after the main shock, afterslip continues at rates several times the average interseismic rate, resulting in deformation equivalent to at least a M_w 8.2 earthquake. In general, along-strike variations in frictional behavior appear to persist over multiple earthquake cycles. Aftershocks cluster along the boundary between the region of coseismic slip and the up-dip creeping zone. We observe that the cumulative number of aftershocks increases linearly with postseismic displacements; this finding suggests that the temporal evolution of aftershocks is governed by afterslip.", "doi": "10.1126/science.1126960", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2006-06-30", "series_number": "5782", "volume": "312", "issue": "5782", "pages": "1921-1926" }, { "id": "authors:xq70t-geh20", "collection": "authors", "collection_id": "xq70t-geh20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-093202330", "type": "article", "title": "Source parameters of the great Sumatran megathrust earthquakes of 1797 and 1833 inferred from coral microatolls", "author": [ { "family_name": "Natawidjaja", "given_name": "Danny Hilman", "clpid": "Natawidjaja-D-H" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Chlieh", "given_name": "Mohamed", "clpid": "Chlieh-M" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" }, { "family_name": "Suwargadi", "given_name": "Bambang W.", "clpid": "Suwargadi-B-W" }, { "family_name": "Cheng", "given_name": "Hai", "clpid": "Cheng-H" }, { "family_name": "Edwards", "given_name": "R. Lawrence", "clpid": "Edwards-R-L" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ward", "given_name": "Steven N.", "clpid": "Ward-S-N" } ], "abstract": "Large uplifts and tilts occurred on the Sumatran outer arc islands between 0.5\u00b0 and 3.3\u00b0S during great historical earthquakes in 1797 and 1833, as judged from relative sea level changes recorded by annually banded coral heads. Coral data for these two earthquakes are most complete along a 160-km length of the Mentawai islands between 3.2\u00b0 and 2\u00b0S. Uplift there was as great as 0.8 m in 1797 and 2.8 m in 1833. Uplift in 1797 extended 370 km, between 3.2\u00b0 and 0.5\u00b0S. The pattern and magnitude of uplift imply megathrust ruptures corresponding to moment magnitudes (M_w) in the range 8.5 to 8.7. The region of uplift in 1833 ranges from 2\u00b0 to at least 3.2\u00b0S and, judging from historical reports of shaking and tsunamis, perhaps as far as 5\u00b0S. The patterns and magnitude of uplift and tilt in 1833 are similar to those experienced farther north, between 0.5\u00b0 and 3\u00b0N, during the giant Nias-Simeulue megathrust earthquake of 2005; the outer arc islands rose as much as 3 m and tilted toward the mainland. Elastic dislocation forward modeling of the coral data yields megathrust ruptures with moment magnitudes ranging from 8.6 to 8.9. Sparse accounts at Padang, along the mainland west coast at latitude 1\u00b0S, imply tsunami runups of at least 5 m in 1797 and 3\u20134 m in 1833. Tsunamis simulated from the pattern of coral uplift are roughly consistent with these reports. The tsunami modeling further indicates that the Indian Ocean tsunamis of both 1797 and 1833, unlike that of 2004, were directed mainly south of the Indian subcontinent. Between about 0.7\u00b0 and 2.1\u00b0S, the lack of vintage 1797 and 1833 coral heads in the intertidal zone demonstrates that interseismic submergence has now nearly equals coseismic emergence that accompanied those earthquakes. The interseismic strains accumulated along this reach of the megathrust have thus approached or exceeded the levels relieved in 1797 and 1833.", "doi": "10.1029/2005JB004025", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2006-06-16", "series_number": "B6", "volume": "111", "issue": "B6", "pages": "Art. No. B06403" }, { "id": "authors:tc4qf-va868", "collection": "authors", "collection_id": "tc4qf-va868", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-095022710", "type": "article", "title": "Mountain building in the Nepal Himalaya: Thermal and kinematic model", "author": [ { "family_name": "Bollinger", "given_name": "L.", "clpid": "Bollinger-L" }, { "family_name": "Henry", "given_name": "P.", "clpid": "Henry-P" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We model crustal deformation and the resulting thermal structure across the Nepal Himalaya, assuming that, since 20 Ma, shortening across the range has been primarily taken up by slip along a single thrust fault, the Main Himalayan Thrust (MHT) Fault, and that the growth of the Himalayan wedge has resulted mainly from underplating and to the development of a duplex at midcrustal depth. We show that this process can account for the inverse thermal metamorphic gradient documented throughout the Lesser Himalaya (LH), the discontinuity of peak metamorphic temperatures across the MCT, as well as the distribution of age of exhumation across the range. This study suggests that the metamorphic evolution of the range over about the last 20 million years is compatible with the kinematics of recent crustal deformation deduced from morphotectonic and geodetic studies.", "doi": "10.1016/j.epsl.2006.01.045", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2006-04-15", "series_number": "1-2", "volume": "244", "issue": "1-2", "pages": "58-71" }, { "id": "authors:1hp17-a0909", "collection": "authors", "collection_id": "1hp17-a0909", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-090803275", "type": "article", "title": "Deformation and Slip Along the Sunda Megathrust in the Great 2005 Nias-Simeulue Earthquake", "author": [ { "family_name": "Briggs", "given_name": "Richard W.", "clpid": "Briggs-R-W" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Meltzner", "given_name": "Aron J.", "orcid": "0000-0002-2955-0896", "clpid": "Meltzner-A-J" }, { "family_name": "Natawidjaja", "given_name": "Danny", "clpid": "Natawidjaja-D-H" }, { "family_name": "Galetzka", "given_name": "John", "clpid": "Galetzka-J" }, { "family_name": "Suwargadi", "given_name": "Bambang", "clpid": "Suwargadi-B-W" }, { "family_name": "Hsu", "given_name": "Ya-Ju", "clpid": "Hsu-Ya-Ju" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Hananto", "given_name": "Nugroho", "clpid": "Hananto-N" }, { "family_name": "Suprihanto", "given_name": "Imam", "clpid": "Suprihanto-I" }, { "family_name": "Prayudi", "given_name": "Dudi", "clpid": "Prayudi-D" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Prawirodirdjo", "given_name": "Linette", "clpid": "Prawirodirdjo-L" }, { "family_name": "Bock", "given_name": "Yehuda", "clpid": "Bock-Y" } ], "abstract": "Seismic rupture produced spectacular tectonic deformation above a 400-kilometer strip of the Sunda megathrust, offshore northern Sumatra, in March 2005. Measurements from coral microatolls and Global Positioning System stations reveal trench-parallel belts of uplift up to 3 meters high on the outer-arc islands above the rupture and a 1-meter-deep subsidence trough farther from the trench. Surface deformation reflects more than 11 meters of fault slip under the islands and a pronounced lessening of slip trenchward. A saddle in megathrust slip separates the northwestern edge of the 2005 rupture from the great 2004 Sumatra-Andaman rupture. The southeastern edge abuts a predominantly aseismic section of the megathrust near the equator.", "doi": "10.1126/science.1122602", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2006-03-31", "series_number": "5769", "volume": "311", "issue": "5769", "pages": "1897-1901" }, { "id": "authors:r4rge-99724", "collection": "authors", "collection_id": "r4rge-99724", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-091646628", "type": "article", "title": "Coseismic surface deformation from air photos: The Kickapoo step over in the 1992 Landers rupture", "author": [ { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Coseismic deformation of the ground can be measured from aerial views taken before and after an earthquake. We chose the area of the Kickapoo-Landers step over along the 1992 Landers earthquake zone, using air photos (scale 1:40,000) scanned at 0.4 m resolution. Two photos acquired after the earthquake are used to assess the accuracy and to evaluate various sources of noise. Optical distortions, film deformation, scanning errors, or errors in viewing parameters can yield metric bias at wavelength larger than 1 km. Offset field at shorter wavelength is more reliable and mainly affected by temporal decorrelation of the images induced by changes in radiometry with time. Temporal decorrelation and resulting uncertainty on offsets are estimated locally from the correlation degree between the images. Relative surface displacements are measured independently every about 15 m and with uncertainty typically below 10 cm (RMS). The offset field reveals most of the surface ruptures mapped in the field. The fault slip is accurate to about 7 cm (RMS) and measured independently every 200 m from stacked profiles. Slip distribution compares well with field measurements at the kilometric scale but reveals local discrepancies suggesting that deformation is generally, although not systematically, localized on the major fault zone located in the field. This type of data can provide useful insight into the fault zone's mechanical properties. Our measurements indicate that elastic coseismic strain near the fault zone can be as large as 0.5 \u00d7 10^(\u22123), while anelastic yielding was attained for strain in excess of about 1\u20132 \u00d7 10^(\u22123).", "doi": "10.1029/2005JB003776", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2006-03-21", "series_number": "B3", "volume": "111", "issue": "B3", "pages": "Art. No. B03408" }, { "id": "authors:zxt63-0wv56", "collection": "authors", "collection_id": "zxt63-0wv56", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-111421546", "type": "article", "title": "Plate-boundary deformation associated with the great Sumatra\u2013Andaman earthquake", "author": [ { "family_name": "Subarya", "given_name": "Cecep", "clpid": "Subarya-C" }, { "family_name": "Chlieh", "given_name": "Mohamed", "clpid": "Chlieh-M" }, { "family_name": "Prawirodirdjo", "given_name": "Linette", "clpid": "Prawirodirdjo-L" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bock", "given_name": "Yehuda", "clpid": "Bock-Y" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Meltzner", "given_name": "Aron J.", "orcid": "0000-0002-2955-0896", "clpid": "Meltzner-A-J" }, { "family_name": "Natawidjaja", "given_name": "Danny H.", "clpid": "Natawidjaja-D-H" }, { "family_name": "McCaffrey", "given_name": "Robert", "clpid": "McCaffrey-R" } ], "abstract": "The Sumatra\u2013Andaman earthquake of 26 December 2004 is the first giant earthquake (moment magnitude M_w > 9.0) to have occurred since the advent of modern space-based geodesy and broadband seismology. It therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events. Here we report estimates of the ground displacement associated with this event, using near-field Global Positioning System (GPS) surveys in northwestern Sumatra combined with in situ and remote observations of the vertical motion of coral reefs. These data show that the earthquake was generated by rupture of the Sunda subduction megathrust over a distance of >1,500 kilometres and a width of <150 kilometres. Megathrust slip exceeded 20 metres offshore northern Sumatra, mostly at depths shallower than 30 kilometres. Comparison of the geodetically and seismically inferred slip distribution indicates that ~30 per cent additional fault slip accrued in the 1.5 months following the 500-second-long seismic rupture. Both seismic and aseismic slip before our re-occupation of GPS sites occurred on the shallow portion of the megathrust, where the large Aceh tsunami originated. Slip tapers off abruptly along strike beneath Simeulue Island at the southeastern edge of the rupture, where the earthquake nucleated and where an M_w = 7.2 earthquake occurred in late 2002. This edge also abuts the northern limit of slip in the 28 March 2005 M_w = 8.7 Nias\u2013Simeulue earthquake.", "doi": "10.1038/nature04522", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2006-03-02", "series_number": "7080", "volume": "440", "issue": "7080", "pages": "46-51" }, { "id": "authors:mnnk8-ene98", "collection": "authors", "collection_id": "mnnk8-ene98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110110-151927244", "type": "article", "title": "Magnetostratigraphy of the Yaha section, Tarim Basin (China): 11 Ma acceleration in erosion and uplift of the Tian Shan mountains", "author": [ { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Gilder", "given_name": "Stuart", "clpid": "Gilder-S" }, { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sen", "given_name": "Sevket", "clpid": "Sen-Sevket" }, { "family_name": "Jolivet", "given_name": "Marc", "clpid": "Jolivet-M" }, { "family_name": "Li", "given_name": "Yongan", "clpid": "Li-Yongan" }, { "family_name": "Wang", "given_name": "Weiming", "clpid": "Wang-Weiming" } ], "abstract": "We report a magnetostratigraphic and rock magnetic study of the Yaha section, located on the southern flank of the central Tian Shan mountains, Asia. Our results show a two-fold increase in sedimentation rate as well as marked changes in rock magnetic characteristics ca. 11 Ma. After 11 Ma, sedimentation rate remained remarkably constant until at least 5.2 Ma. These findings are consistent with sedimentary records from other sections surrounding the Tian Shan. We conclude that uplift and erosion of the Tian Shan accelerated ca. 11 Ma, long after the onset of the collision between India and Asia, and that the range rapidly evolved toward a steady-state geometry via a balance between tectonic and erosion processes.", "doi": "10.1130/G22106.1", "issn": "0091-7613", "publisher": "Geological Society of America", "publication": "Geology", "publication_date": "2006-03", "series_number": "3", "volume": "34", "issue": "3", "pages": "181-184" }, { "id": "authors:0dye0-ek952", "collection": "authors", "collection_id": "0dye0-ek952", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101117-114453223", "type": "article", "title": "Uplift and subsidence associated with the great Aceh-Andaman earthquake of 2004", "author": [ { "family_name": "Meltzner", "given_name": "Aron J.", "orcid": "0000-0002-2955-0896", "clpid": "Meltzner-A-J" }, { "family_name": "Sieh", "given_name": "Kerry", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Abrams", "given_name": "Michael", "clpid": "Abrams-M-J" }, { "family_name": "Agnew", "given_name": "Duncan C.", "clpid": "Agnew-D-C" }, { "family_name": "Hudnut", "given_name": "Kenneth W.", "orcid": "0000-0002-3168-4797", "clpid": "Hudnut-K-W" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Natawidjaja", "given_name": "Danny H.", "clpid": "Natawidjaja-D-H" } ], "abstract": "Rupture of the Sunda megathrust on 26 December 2004 produced broad regions of uplift and subsidence. We define the pivot line separating these regions as a first step in defining the lateral extent and the downdip limit of rupture during that great M_w \u2248 9.2 earthquake. In the region of the Andaman and Nicobar islands we rely exclusively on the interpretation of satellite imagery and a tidal model. At the southern limit of the great rupture we rely principally on field measurements of emerged coral microatolls. Uplift extends from the middle of Simeulue Island, Sumatra, at ~2.5\u00b0N, to Preparis Island, Myanmar (Burma), at ~14.9\u00b0N. Thus the rupture is ~1600 km long. The distance from the pivot line to the trench varies appreciably. The northern and western Andaman Islands rose, whereas the southern and eastern portion of the islands subsided. The Nicobar Islands and the west coast of Aceh province, Sumatra, subsided. Tilt at the southern end of the rupture is steep; the distance from 1.5 m of uplift to the pivot line is just 60 km. Our method of using satellite imagery to recognize changes in elevation relative to sea surface height and of using a tidal model to place quantitative bounds on coseismic uplift or subsidence is a novel approach that can be adapted to other forms of remote sensing and can be applied to other subduction zones in tropical regions.", "doi": "10.1029/2005JB003891", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2006-02-15", "series_number": "B2", "volume": "111", "issue": "B2", "pages": "Art. No. B02407" }, { "id": "authors:cxxpj-9j813", "collection": "authors", "collection_id": "cxxpj-9j813", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120906-142549966", "type": "article", "title": "Numerical modelling of quaternary deformation and post-rifting displacement in the Asal\u2013Ghoubbet rift (Djibouti, Africa)", "author": [ { "family_name": "Cattin", "given_name": "Rodolphe", "clpid": "Cattin-R" }, { "family_name": "Doubre", "given_name": "C\u00e9cile", "clpid": "Doubre-C" }, { "family_name": "de Chabalier", "given_name": "Jean-Bernard", "clpid": "de-Chabalier-J-B" }, { "family_name": "King", "given_name": "Geoffrey", "orcid": "0000-0002-5327-7631", "clpid": "King-G" }, { "family_name": "Vigny", "given_name": "Christophe", "clpid": "Vigny-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ruegg", "given_name": "Jean-Claude", "clpid": "Ruegg-J-C" } ], "abstract": "Over the last three decades a host of information on rifting process relating to the geological and thermal structure, long-time scale deformation (Quaternary and Holocene) and rifting cycle displacement across the Asal\u2013Ghoubbet rift has been made available. These data are interpreted with a two-dimensional thermo-mechanical model that incorporates rheological layering of the lithosphere, dyke inflation and faulting. Active fault locations and geometry are mainly controlled by both thermal structure and magma intrusion into the crust. The distributed slip throughout the inner rift is related to the closeness of magma chamber, leading to additional stress into the upper thinned crust. Assuming a constant Arabia\u2013Somalia motion of 11 mm/year, the variation of subsidence rate between the last 100 and 9 ka is associated with a decrease of the average injection rate from 10 to 5 mm/year. These values, about equal to the regional opening rate, suggest that both volcanism and tectonic play an equivalent role in the rifting process. Our modelled sequence of events gives one possible explanation for both vertical and horizontal displacements observed since the 1978 seismovolcanic crisis. Although part of the post-rifting deformation could be due to viscous relaxation, the high opening rate in the first years after the event and the abrupt velocity change in 1984\u20131986 argue for a large dyke inflation of 12 cm/year ending in 1985. The asymmetric and constant pattern of the GPS velocity since 1991 suggests that present post-rifting deformation is mainly controlled by fault creep and regional stretching. This study demonstrates the internal consistency of the data set, highlights the role of magmatism in the mechanics of crustal stretching and reveals a complex post-rifting process including magma injection, fault creep and regional stretching.", "doi": "10.1016/j.epsl.2005.07.028", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2005-11-15", "series_number": "3-4", "volume": "239", "issue": "3-4", "pages": "352-367" }, { "id": "authors:zhdkf-njp26", "collection": "authors", "collection_id": "zhdkf-njp26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101118-073601530", "type": "article", "title": "Geodetic displacements and aftershocks following the 2001 M_w = 8.4 Peru earthquake: Implications for the mechanics of the earthquake cycle along subduction zones", "author": [ { "family_name": "Perfettini", "given_name": "H.", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ruegg", "given_name": "J.-C.", "clpid": "Ruegg-J-C" } ], "abstract": "We analyzed aftershocks and postseismic deformation recorded by the continuous GPS station AREQ following the M_w = 8.4, 23 June 2001 Peru earthquake. This station moved by 50 cm trenchward, in a N235\u00b0E direction during the coseismic phase, and continued to move in the same direction for an additional 15 cm over the next 2 years. We compare observations with the prediction of a simple one-dimensional (1-D) system of springs, sliders, and dashpot loaded by a constant force, meant to simulate stress transfer during the seismic cycle. The model incorporates a seismogenic fault zone, obeying rate-weakening friction, a zone of deep afterslip, the brittle creep fault zone (BCFZ) obeying rate-strengthening friction, and a zone of viscous flow at depth, the ductile fault zone (DFZ). This simple model captures the main features of the temporal evolution of seismicity and deformation. Our results imply that crustal strain associated with stress accumulation during the interseismic period is probably not stationary over most of the interseismic period. The BCFZ appears to control the early postseismic response (afterslip and aftershocks), although an immediate increase, by a factor of about 1.77, of ductile shear rate is required, placing constraints on the effective viscosity of the DFZ. Following a large subduction earthquake, displacement of inland sites is trenchward in the early phase of the seismic cycle and reverse to landward after a time t i for which an analytical expression is given. This study adds support to the view that the decay rate of aftershocks may be controlled by reloading due to deep afterslip. Given the ratio of preseismic to postseismic viscous creep, we deduce that frictional stresses along the subduction interface account for probably 70% of the force transmitted along the plate interface.", "doi": "10.1029/2004JB003522", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2005-09-03", "series_number": "B9", "volume": "110", "issue": "B9", "pages": "Art. No. B09404" }, { "id": "authors:a81fr-8ak04", "collection": "authors", "collection_id": "a81fr-8ak04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110110-152743244", "type": "article", "title": "Magnetostratigraphy and rock magnetism of the Neogene Kuitun He section (northwest China): implications for Late Cenozoic uplift of the Tianshan mountains", "author": [ { "family_name": "Charreau", "given_name": "Julien", "clpid": "Charreau-J" }, { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Gilder", "given_name": "Stuart", "clpid": "Gilder-S" }, { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sen", "given_name": "Sevket", "clpid": "Sen-Sevket" }, { "family_name": "Sun", "given_name": "Dongjiang", "clpid": "Sun-Dongjiang" }, { "family_name": "Li", "given_name": "Yongan", "clpid": "Li-Yongan" }, { "family_name": "Wang", "given_name": "Wei-Ming", "clpid": "Wang-Wei-Ming" } ], "abstract": "In order to better constrain the tectonic evolution of central Asia under the influence of the India\u2013Asia collision, we carried out a magnetostratigraphic study at the Kuitun He section, on the northern flank of the Tianshan range (northwest China). A total of 801 samples were collected from a 1559-m-thick section, which is composed mainly of fluvio-lacustrine sandstone and conglomerate. Stepwise thermal and alternating field demagnetization isolated a linear magnetization component that decays univectorally toward the origin and likely represents a primary magnetization principally carried by magnetite. From this component, 29 magnetic polarity intervals were identified. They correlate between ~3.1 and ~10.5 Ma with the reference magnetic polarity time scale, indicating a relatively constant sedimentation rate with an average of 0.21\u00b10.01 mm/year. We also performed a suite of rock magnetic experiments designed to track time-transgressive changes in the sedimentary record. From the rock magnetic parameters, together with the constant sedimentation rate, we conclude that the Tianshan mountains were actively uplifting by ~10.5 Ma.", "doi": "10.1016/j.epsl.2004.11.002", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2005-01-30", "series_number": "1-2", "volume": "230", "issue": "1-2", "pages": "177-192" }, { "id": "authors:fjy26-1n302", "collection": "authors", "collection_id": "fjy26-1n302", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120906-134247472", "type": "article", "title": "A Probabilistic Approach to Seismic Hazard in Metropolitan France", "author": [ { "family_name": "Marin", "given_name": "Sylvie", "clpid": "Marin-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Nicolas", "given_name": "Marc", "clpid": "Nicolas-M" }, { "family_name": "Schlupp", "given_name": "Antoine", "clpid": "Schlupp-A" } ], "abstract": "In this study, we applied a probabilistic methodology to seismic hazard assessment in metropolitan France. For that purpose we determined an attenuation law adapted to the French context. This law holds for peak ground acceleration on stiff bedrock for earthquakes with local magnitudes between 2.5 and 5.6 recorded in near field (at distances between 3 and 50 km). Geological conditions are taken into account by means of a three-categories classification of lithologies based on a 1/1,000,000 geological map. The seismotectonic zonation consists of areas of diffuse seismicity characterized by a frequency-magnitude distribution. In southeastern France, active faults are considered in a test case and are assumed to follow the characteristic earthquake model. We performed hazard curves for six French cities and maps of peak horizontal ground accelerations expected for return periods of 475, 975, and 1975 years in the country. Sensitivity tests have been performed. The uncertainty introduced by ground-motion variability seems minor compared with that due to the choice of the attenuation law. This study points to the importance of testing internal consistency of the various data and laws used in any seismic hazard analysis (in particular, here the type of magnitude used to predict ground motion). If not, some systematic bias is introduced that may result in systematic errors on peak ground acceleration determination. We also show that the introduction of possibly very large and infrequent events, known only from paleoseismic investigations, may have a dramatic impact on the hazard, especially when long periods of time are considered.", "doi": "10.1785/0120030232", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "2004-12", "series_number": "6", "volume": "94", "issue": "6", "pages": "2137-2163" }, { "id": "authors:xd2mh-tw228", "collection": "authors", "collection_id": "xd2mh-tw228", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101118-110717109", "type": "article", "title": "Tectonic evolution of a continental collision zone: A thermomechanical numerical model", "author": [ { "family_name": "Toussaint", "given_name": "G.", "clpid": "Toussaint-G" }, { "family_name": "Burov", "given_name": "E.", "clpid": "Burov-E" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We model evolution of a continent-continent collision and draw some parallels with the tectonic evolution of the Himalaya. We use a large-scale visco-plasto-elastic thermomechanical model that has a free upper surface, accounts for erosion and deposition and allows for all modes of lithospheric deformation. For quartz/olivine rheology and 60 mm/yr convergence rate, the continental subduction is stable, and the model predicts three distinct phases. During the phase 1 (120 km or 6% of shortening), deformation is characterized by back thrusting around the suture zone. Some amount of delaminated lower crust accumulates at depth. During phase 2 (120 km\u2013420 km or 6%\u201322% of shortening), this crustal root is exhumed (medium- to high-grade rocks) along a newly formed major thrust fault. This stage bears similarities with the period of coeval activity of the Main Central thrust and of the South Tibetan Detachment between 20\u201316 Myr ago. During phase 3 (>420 km or 22% of shortening), the crust is scraped off from the mantle lithosphere and is incorporated into large crustal wedge. Deformation is localized around frontal thrust faults. This kinematics should produce only low- to medium-grade exhumation. This stage might be compared with the tectonics that has prevailed in the Himalaya over the last 15 Myr allowing for the formation of the Lesser Himalaya. The experiment is conducted at constant convergence rate, which implies increasing compressive force. Considering that this force is constant in nature, this result may be equivalent to a slowing down of the convergence rate as was observed during the India-Asia collision.", "doi": "10.1029/2003TC001604", "issn": "0278-7407", "publisher": "American Geophysical Union", "publication": "Tectonics", "publication_date": "2004-11-30", "series_number": "6", "volume": "23", "issue": "6", "pages": "Art. No. TC6003" }, { "id": "authors:4r8sp-0bv25", "collection": "authors", "collection_id": "4r8sp-0bv25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101118-132506328", "type": "article", "title": "Stress buildup in the Himalaya", "author": [ { "family_name": "Bollinger", "given_name": "L.", "clpid": "Bollinger-L" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Cattin", "given_name": "R.", "clpid": "Cattin-R" }, { "family_name": "Pandey", "given_name": "M. R.", "clpid": "Pandey-M-R" } ], "abstract": "The seismic cycle on a major fault involves long periods of elastic strain and stress accumulation, driven by aseismic ductile deformation at depth, ultimately released by sudden fault slip events. Coseismic slip distributions are generally heterogeneous with most of the energy being released in the rupture of asperities. Since, on the long term, the fault's walls generally do not accumulate any significant permanent deformation, interseismic deformation might be heterogeneous, revealing zones of focused stress buildup. The pattern of current deformation along the Himalayan arc, which is known to produce recurring devastating earthquakes, and where several seismic gaps have long been recognized, might accordingly show significant lateral variations, providing a possible explanation for the uneven microseismic activity along the Himalayan arc. By contrast, the geodetic measurements show a rather uniform pattern of interseismic strain, oriented consistently with long-term geological deformation, as indicated from stretching lineation. We show that the geodetic data and seismicity distribution are reconciled from a model in which microseismicity is interpreted as driven by stress buildup increase in the interseismic period. The uneven seismicity pattern is shown to reflect the impact of the topography on the stress field, indicating low deviatoric stresses (<35 MPa) and a low friction (<0.3) on the Main Himalayan Thrust. Arc-normal thrusting along the Himalayan front and east-west extension in southern Tibet are quantitatively reconciled by the model.", "doi": "10.1029/2003JB002911", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2004-11-20", "series_number": "B11", "volume": "109", "issue": "B11", "pages": "Art. No. B11405" }, { "id": "authors:f2ewd-67q31", "collection": "authors", "collection_id": "f2ewd-67q31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110111-091600174", "type": "article", "title": "Thermal structure and exhumation history of the Lesser Himalaya in central Nepal", "author": [ { "family_name": "Bollinger", "given_name": "L.", "clpid": "Bollinger-L" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Beyssac", "given_name": "O.", "clpid": "Beyssac-O" }, { "family_name": "Catlos", "given_name": "E. J.", "clpid": "Catlos-E-J" }, { "family_name": "Harrison", "given_name": "T. M.", "clpid": "Harrison-T-M" }, { "family_name": "Grove", "given_name": "M.", "clpid": "Grove-M" }, { "family_name": "Goff\u00e9", "given_name": "B.", "clpid": "Goff\u00e9-B" }, { "family_name": "Sapkota", "given_name": "S.", "clpid": "Sapkota-S" } ], "abstract": "The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ~20 Myr. It now forms a significant fraction of the Himalayan collisional orogen. We document the kinematics and thermal metamorphism associated with the deformation and exhumation of the LH, combining thermometric and thermochronological methods with structural geology. Peak metamorphic temperatures estimated from Raman spectroscopy of carbonaceous material decrease gradually from 520\u00b0\u2013550\u00b0C below the Main Central Thrust zone down to less than 330\u00b0C. These temperatures describe structurally a 20\u00b0\u201350\u00b0C/km inverted apparent gradient. The Ar muscovite ages from LH samples and from the overlying crystalline thrust sheets all indicate the same regular trend; i.e., an increase from about 3\u20134 Ma near the front of the high range to about 20 Ma near the leading edge of the thrust sheets, about 80 km to the south. This suggests that the LH has been exhumed jointly with the overlying nappes as a result of overthrusting by about 5 mm/yr. For a convergence rate of about 20 mm/yr, this implies underthrusting of the Indian basement below the Himalaya by about 15 mm/yr. The structure, metamorphic grade and exhumation history of the LH supports the view that, since the mid-Miocene, the Himalayan orogen has essentially grown by underplating, rather than by frontal accretion. This process has resulted from duplexing at a depth close to the brittle-ductile transition zone, by southward migration of a midcrustal ramp along the Main Himalayan Thrust fault, and is estimated to have resulted in a net flux of up to 150 m^2/yr of LH rocks into the Himalayan orogenic wedge. The steep inverse thermal gradient across the LH is interpreted to have resulted from a combination of underplating and post metamorphic shearing of the underplated units.", "doi": "10.1029/2003TC001564", "issn": "0278-7407", "publisher": "American Geophysical Union", "publication": "Tectonics", "publication_date": "2004-10-20", "series_number": "5", "volume": "23", "issue": "5", "pages": "Art. No. TC5015" }, { "id": "authors:5y5h1-v4655", "collection": "authors", "collection_id": "5y5h1-v4655", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101118-135335005", "type": "article", "title": "The Sumatra subduction zone: A case for a locked fault zone extending into the mantle", "author": [ { "family_name": "Simoes", "given_name": "Martine", "clpid": "Simoes-M" }, { "family_name": "Avouac", "given_name": "Jean Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Cattin", "given_name": "Rodolphe", "clpid": "Cattin-R" }, { "family_name": "Henry", "given_name": "Pierre", "clpid": "Henry-P" } ], "abstract": "A current view is that the portion of the subduction interface that remains locked in the time interval between large interplate earthquakes, hereinafter referred to as the locked fault zone (LFZ), does not extend into the mantle because serpentinization of the mantle wedge would favor stable aseismic sliding. Here, we test this view in the case of the Sumatra subduction zone where the downdip end of the LFZ can be well constrained from the pattern and rate of uplift deduced from coral growth and from GPS measurements of horizontal deformation. These geodetic data are modeled from a creeping dislocation embedded in an elastic half-space and indicate that the LFZ extends 132 \u00b1 10/7 km from the trench, to a depth between 35 and 57 km. By combining this information with the geometry of the plate interface as constrained from two-dimensional gravimetric modeling and seismicity, we show that the LFZ extends below the forearc Moho, which is estimated to lie at a depth of ~30 km, at a horizontal distance of 110 km from the trench. So, in this particular island arc setting, the LFZ most probably extends into the mantle, implying that either the mantle is not serpentinized, or that the presence of serpentine does not necessarily imply stable sliding. From thermal modeling, the temperature at the downdip end of the LFZ is estimated to be 260 \u00b1 100\u00b0C. This temperature seems too low for thermally activated ductile flow, so that aseismic slip is most probably due to pressure and/or temperature induced steady state brittle sliding, possibly favored by fluids released from the subducting slab.", "doi": "10.1029/2003JB002958", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2004-10-02", "series_number": "B10", "volume": "109", "issue": "B10", "pages": "Art. No. B10402" }, { "id": "authors:976et-ea184", "collection": "authors", "collection_id": "976et-ea184", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110111-092509212", "type": "article", "title": "Thermal metamorphism in the lesser Himalaya of Nepal determined from Raman spectroscopy of carbonaceous material", "author": [ { "family_name": "Beyssac", "given_name": "Olivier", "clpid": "Beyssac-O" }, { "family_name": "Bollinger", "given_name": "Laurent", "clpid": "Bollinger-L" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Goff\u00e9", "given_name": "Bruno", "clpid": "Goff\u00e9-B" } ], "abstract": "The determination of metamorphic conditions is critical to the understanding of the formation of mountain belts. However, all collisional mountain belts contain large volumes of accreted sediments generally lacking metamorphic index minerals and are therefore not amenable to conventional petrologic investigations. By contrast, these units are often rich in carbonaceous material, making it possible to determine thermal metamorphism through Raman spectroscopy of carbonaceous material (RSCM method), a technique that has been recently calibrated [Beyssac et al., J. Metamorph. Geol. 20 (2002) 859\u2013871]. The Lesser Himalaya (LH) is one of these problematic cases with a very poor mineralogy, but a key structural position within the Himalayan system that makes LH considered as diagnostic of the overall thermal behaviour of the orogen. This work demonstrates the performance of the RSCM technique and shows that this technique might thus be used to detect inter-sample variations as small as ~10\u201315 \u00b0C, but absolute temperatures can only be determined to \u00b150 \u00b0C due to the uncertainty on the calibration. This study reveals that the LH has undergone a large-scale thermal metamorphism, with temperature decreasing progressively from about 540 \u00b0C at the top to less than 330 \u00b0C within the deepest exhumed structural levels.", "doi": "10.1016/j.epsl.2004.05.023", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2004-08-30", "series_number": "1-2", "volume": "225", "issue": "1-2", "pages": "233-241" }, { "id": "authors:hav8t-9vb15", "collection": "authors", "collection_id": "hav8t-9vb15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110110-161256950", "type": "article", "title": "Stress transfer and strain rate variations during the seismic cycle", "author": [ { "family_name": "Perfettini", "given_name": "H.", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The balance of forces implies stress transfers during the seismic cycle between the elastobrittle upper crust and the viscoelastic lower crust. This could induce observable time variations of crustal straining in the interseismic period. We simulate these variations using a one-dimensional system of springs, sliders, and dashpot loaded by a constant force. The seismogenic zone and the zone of afterslip below are modeled from rate-and-state friction. The ductile deeper fault zone is modeled from a viscous slider with Newtonian viscosity \u03bd. The force per unit length, F, must exceed a critical value F_c to overcome friction resistance of the fault system. This simple system produces periodic earthquakes. The recurrence period, T_(cycle), and the duration of the postseismic relaxation phase, which is driven dominantly by afterslip, then both scale linearly with \u03bd. Between two earthquakes, interseismic strain buildup across the whole system is nonstationary with the convergence rates V_i, just after each earthquake, being systematically higher than the value V_f at the end of the interseismic period. We show that V_i/V_f is an exponential function of \u03b1 = T_(cycle)/T_M \u221d \u0394\u03c4/(F \u2013 F_c ) \u221d \u0394\u03c4/(\u03bdV_ 0), where \u0394\u03c4 is the coseismic stress drop and V_0 is the long-term fault slip rate. It follows that departure from stationary strain buildup is higher if the contribution of viscous forces to the force balance is small compared to the coseismic stress drop (due to a low viscosity or low convergence rate, for example). This simple model is meant to show that the far-field deformation rate in the interseismic period, which can be determined from geodetic measurements, might not necessarily be uniform and equal to the long-term geologic rate.", "doi": "10.1029/2003JB002917", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2004-06-22", "series_number": "B6", "volume": "109", "issue": "B6", "pages": "Art. No. B06402" }, { "id": "authors:jep2g-ck669", "collection": "authors", "collection_id": "jep2g-ck669", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110110-155620364", "type": "article", "title": "Current shortening across the Himalayas of Nepal", "author": [ { "family_name": "Jouanne", "given_name": "F.", "clpid": "Jouanne-F" }, { "family_name": "Mugnier", "given_name": "J. L.", "clpid": "Mugnier-J-L" }, { "family_name": "Gamond", "given_name": "J. F.", "clpid": "Gamond-J-F" }, { "family_name": "Le Fort", "given_name": "P.", "clpid": "Le-Fort-P" }, { "family_name": "Pandey", "given_name": "M. R.", "clpid": "Pandey-M-R" }, { "family_name": "Bollinger", "given_name": "L.", "clpid": "Bollinger-L" }, { "family_name": "Flouzat", "given_name": "M.", "clpid": "Flouzat-M" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Underthrusting of the Indian lithosphere beneath the Himalayas occurs during the Quaternary period along a gently north-dipping main basal detachment (main Himalayan thrust: MHT), from which the southernmost emergent ramp (main frontal thrust: MFT) branches. Historical seismicity shows that slip on the MHT is frequently accommodated through M > 8 shallow earthquakes, but shows a seismic gap in western Nepal. This absence of major historical earthquakes in western Nepal can be explained either by an aseismic slip on the MHT or a long-lived elastic strain accumulation. To test these hypotheses, the present-day displacement field has been measured for a GPS network formed of 35 sites. The updated solution presented in this paper combines data from 1995, 1997, 1998 and 2000 measurements. The lack of deformation (less than 3 \u2022 10^(\u22128) yr^(\u22121)) through the outer belt does not fit with a regional aseismic slip along the southern part of MHT. A less than 3 mm yr^(\u22121) aseismic slip could nonetheless affect restricted areas of the outer belt. In contrast, a strain accumulation of more than 30 \u2022 10^(\u22128) yr^(\u22121) is measured south of the Higher Himalayas, in a zone where an intense microseismicity reflects a stress build-up. It is presumably generated by locking of the aseismic creep that occurs along the MHT beneath the Higher Himalayas and Tibet. The displacement field is simulated by a dual-dislocation model that takes into account the pattern of microseismicity, and particularly a segmentation between central and western Nepal. The best fit between the measured and simulated displacement fields is obtained with 19 mm yr^(\u22121) thrust and 0\u20131 mm yr^(\u22121) dextral strike-slip components along a 117\u00b0NE dislocation locked to a depth of 20\u201321 km beneath western Nepal, and 19\u201320 mm yr^(\u22121) thrust and 0\u20132 mm yr^(\u22121) dextral strike-slip components along a 108\u00b0NE dislocation locked to a depth of 17\u201321 km beneath central Nepal. The width of the locked zone between the main frontal thrust and the creeping zone is of the same order, but rather greater, in western Nepal than in central Nepal. Therefore it is expected that M > 8 earthquakes could occur in western Nepal.", "doi": "10.1111/j.1365-246X.2004.02180.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2004-04", "series_number": "1", "volume": "157", "issue": "1", "pages": "1-14" }, { "id": "authors:0f5gb-4kx76", "collection": "authors", "collection_id": "0f5gb-4kx76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110110-154436486", "type": "article", "title": "Holocene Hydrological Changes Inferred from Alluvial Stream Entrenchment in North Tian Shan (Northwestern China)", "author": [ { "family_name": "Poisson", "given_name": "Blanche", "clpid": "Poisson-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We analyze the possible contribution of climate change or tectonics on fluvial incision from the study of a case example along the northern flank of Tian Shan. The rivers that exit the high range fed large alluvial fans by the end of the last glacial period. They have since deeply entrenched the piedmont by as much as 300 m. We have surveyed several terraces that were cut and abandoned during river entrenchment, providing information on intermediate positions of the riverbed during downcutting. They suggest a gradual decline in river slope during a major phase of incision throughout the Holocene. Tectonic uplift affects only a zone about 5 km wide, corresponding to a growing anticline, and is shown to account for about 10% of total incision. Incision was therefore most probably driven by climate change. From observed fluvial incision, we estimate the water discharge in excess of that needed to carry the sediments supplied by hillslope erosion in the headwaters. We used a model based on a transport\u2010limited erosion law. The model predicts relaxation process with entrenchment in the upper reach, downstream progradation of the incision\u2010sedimentation line, and a progressive decrease of river slope during incision consistent with our observations. According to this model, river slope might be used as a proxy for specific discharge and then for volumetric discharge, provided that an assumption is made about river width variations. We conclude that river incision in the study area has resulted from dynamic adjustment of the hydrological system to the settlement of wetter conditions in the early Holocene, when water discharge might have been about three times as high as at present. Then, a rather arid climate with enhanced seasonality has likely prevailed from the mid\u2010Holocene (~6 ka B.P.) until now.", "doi": "10.1086/381659", "issn": "0022-1376", "publisher": "University of Chicago Press", "publication": "Journal of Geology", "publication_date": "2004-03", "series_number": "2", "volume": "112", "issue": "2", "pages": "231-249" }, { "id": "authors:bmjaq-wxg43", "collection": "authors", "collection_id": "bmjaq-wxg43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101123-100006593", "type": "article", "title": "Postseismic relaxation driven by brittle creep: A possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks, application to the Chi-Chi earthquake, Taiwan", "author": [ { "family_name": "Perfettini", "given_name": "H.", "orcid": "0000-0001-6829-5472", "clpid": "Perfettini-H" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We evaluate the effect of coseismic stress changes on the fault slip at midcrustal depth, assuming a velocity-strengthening brittle creep rheology. We show that this model can help reconcile the time evolution of afterslip, as measured from geodesy, with aftershocks decay. We propose an analytical expression for slip of the brittle creeping fault zone (BCFZ) that applies to any dynamic or static stress perturbation, including shear stress and normal stress changes. The model predicts an initial logarithmic increase of slip with time. Postseismic slip rate decays over a characteristic time t_r = a\u03c3/\u03c4 that does not depend on the amplitude of the stress perturbation, and it asymptotically joins the long-term creep imposed by interseismic stress buildup \u03c4. Given that the seismicity rate might be considered proportional to the sliding velocity of the BCFZ, the model predicts a decay rate of aftershocks that follows Omori's law, with a mathematical formalism identical to that of Dieterich [1994] although based on a different mechanical rationale. Our model also differs from Dieterich's model in that it requires that aftershock sequences and deep afterslip, as constrained from geodetic measurements, should follow the same temporal evolution. We test this for the 1999 Chi-Chi earthquake, M_w = 7.6 and find that both sets of data are consistent with a model of afterslip due to the response of the BCFZ. The inferred relaxation time t_r = 8.5 years requires a value for a = \u2202\u03bc/\u2202log(V) (\u03bc being the coefficient of friction) in the range between 1.3 10^(\u22123) and 10^(\u22122).", "doi": "10.1029/2003JB002488", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2004-02-03", "series_number": "B2", "volume": "109", "issue": "B2", "pages": "Art. No. B02304" }, { "id": "authors:0xnwn-x0754", "collection": "authors", "collection_id": "0xnwn-x0754", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120906-104039515", "type": "article", "title": "Alluvial deposition and lake-level fluctuations forced by Late Quaternary climate change: the Dead Sea case example", "author": [ { "family_name": "Klinger", "given_name": "Y.", "clpid": "Klinger-Y" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bourles", "given_name": "D.", "clpid": "Bourles-D" }, { "family_name": "Tisnerat", "given_name": "N.", "clpid": "Tisnerat-N" } ], "abstract": "Based on geomorphic observations, we discuss lake-level fluctuations, alluvial deposition and river entrenchment in the Dead Sea\u2013Wadi Araba area. The bulk of alluvium in the northern Wadi Araba was probably deposited before the Lisan period of lake transgression that started at about 70 kyears B.P. The lake reached a maximum elevation about 150 m below sea level (b.s.l.), possibly around 15 cal. kyears B.P. as indicated by the highest preserved beach ridges. Cosmogenic exposure dates show that the ridge material consists mainly of remobilized Pleistocene gravel indicating little sediment supply during most of the Lisan period. During this period, a reduced sediment flux fed subaquatic fan deltas along the margin of the Dead Sea. Wetter conditions settled at the end of this period, the water level rose to about 280 m b.s.l. around 15 kyears B.P. and prevailed in the early Holocene (10.5\u20137 cal. kyears B.P.). Following that humid period, the lake level dropped and two major episodes of fluvial aggradation occurred during periods of relative low lake level. The first aggradational episode took place between about 7.0 and 6.2 cal. kyears B.P. Beach bars indicate a subsequent lake transgression between 6.2 and 4.4 kyears B.P. up to 350 m b.s.l. The second aggradational episode happened between 4.4 and 2.0 cal. kyears B.P., and was also followed by a late transgression up to 375 m b.s.l., dated to 1960\u20131715 cal. years B.P. The correlation between low lake level and fluvial aggradation is taken to reflect the synchronous change of the fluvial regime and of the lake hydrologic balance, forced by climate changes, rather than a base-level control. We also exclude large tectonic forcing on fan emplacement and river entrenchment. Alluviation appears in this setting as a very irregular process, characterized by long periods of quiescence alternating with periods of fan build-up, reflecting the transient response of the water drainage system to climate change.", "doi": "10.1016/j.sedgeo.2003.07.001", "issn": "0037-0738", "publisher": "Elsevier", "publication": "Sedimentary Geology", "publication_date": "2003-11-01", "series_number": "1-2", "volume": "162", "issue": "1-2", "pages": "119-139" }, { "id": "authors:93fey-qm566", "collection": "authors", "collection_id": "93fey-qm566", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110111-101706941", "type": "article", "title": "Horizontal coseismic deformation of the 1999 Chi-Chi earthquake measured from SPOT satellite images: Implications for the seismic cycle along the western foothills of central Taiwan", "author": [ { "family_name": "Dominguez", "given_name": "St\u00e9phane", "clpid": "Dominguez-S" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" } ], "abstract": "The 1999 Chi-Chi earthquake, M_w = 7.6, broke a major thrust fault along the western foothills of the Central Range of Taiwan. We have measured the horizontal coseismic displacement field by correlating optical satellite images acquired before and after the earthquake. These data reveal the fault trace and a clockwise rotation of surface displacements toward the north with much larger displacements and strain in the hanging wall. At the surface, coseismic slip increases from 5\u20136 m near the epicenter to 10\u201311 m to the north. In the epicentral area, we observe a left-lateral strike-slip zone trending N125\u00b0E, and farther north, a fault zone trending N-S with a right-lateral component. The data were modeled using elastic dislocations. The fault geometry consists of a shallow 20\u201335\u00b0 east dipping ramp, which soles out into a low dipping d\u00e9collement at a depth of ~6 to 8 km. Surface displacements can be satisfactorily modeled, assuming a constant slip azimuth on the main fault plane, close to the azimuth of plate convergence (N305\u00b0E \u00b1 5\u00b0). At depth, slips along the fault plane evolve from 5\u20136 m in the south to 7 to 12 m to the north. Our model suggests that the deeper portion of the fault was not activated during the Chi-Chi earthquake. This zone of slip deficit must break during large earthquakes or be activated during transient episodes of aseismic slip. On the basis of these observations, the western front of the central Taiwan should produce a M = 7 to 7.5 event, about every 150 to 250 years.", "doi": "10.1029/2001JB000951", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2003-02-07", "series_number": "B2", "volume": "108", "issue": "B2", "pages": "Art. No. 2083" }, { "id": "authors:ekddc-cjt77", "collection": "authors", "collection_id": "ekddc-cjt77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120907-140226503", "type": "article", "title": "Fluid flow near reservoir lakes inferred from the spatial and temporal analysis of the electric potential", "author": [ { "family_name": "Trique", "given_name": "Micha\u00ebl", "clpid": "Trique-M" }, { "family_name": "Perrier", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Perrier-F" }, { "family_name": "Froidefond", "given_name": "Thierry", "clpid": "Froidefond-T" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Hautot", "given_name": "Sophie", "clpid": "Hautot-S" } ], "abstract": "Electric self-potential (SP) variations have been monitored continuously from 1995 to 1998 at 14 points on a ridge separating the Roselend and La Gittaz reservoir lakes in the French Alps. The lakes have level variations of at least 50 m over yearly cycles. Seasonal variations of SP associated with lake-level variations are observed on five points of the array. For three points located on the banks of the lakes, a positive correlation to the lake-level variations is observed with a maximal amplitude of about 180 mV, corresponding to an average response of 2.4 mV per meter of water. For two points located on the bottom of each lake, the correlation is negative, with a maximal magnitude of about \u221250 mV, corresponding to an average response of \u22121.1 mV per meter of water. Two independent temporary electrical arrays located on the banks of each lake confirm these measurements and allow a better spatial characterization of the sources associated with the observed SP variations. In particular, near the Roselend lake, the electrical response to lake-level variations is increasing for decreasing altitude. The measured SP variations are proposed to result from the electrokinetic coupling associated with a vertical groundwater flow connecting a constant pore pressure source to the bottom of the lakes. Numerical modeling indicates that the spatial variation of the response and the nonlinear response observed at one point can be explained by leakage currents in the conductive lake water. The values of the streaming potential coefficient (SPC), measured in the laboratory with crushed rock samples from the site, range from 14 to 50 mV/0.1 MPa for an electrolyte resistivity of 40 \u03a9 m and are compatible, to first order, with the magnitude of the observed seasonal SP variations. A detailed quantitative electrokinetic modeling is currently limited mainly by the poor knowledge on the contribution of electrical leakage currents and the local variability of the SPC. This experiment indicates that spatial and temporal variations of the electric potential are promising tools to characterize and monitor shallow groundwater flow and provide practical data for the investigation of groundwater flow associated with volcanic or tectonic activity.", "doi": "10.1029/2001JB000482", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2002-10", "series_number": "B10", "volume": "107", "issue": "B10", "pages": "Art. No. 2239" }, { "id": "authors:eqqmg-45y35", "collection": "authors", "collection_id": "eqqmg-45y35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-102105821", "type": "article", "title": "Deformation due to the 17 August 1999 Izmit, Turkey, earthquake measured from SPOT images", "author": [ { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The geometry of the ruptured areas and the coseismic slip distribution data are key to highlighting the behavior of seismic faults. This information is generally retrieved from field investigations and geodetic measurements or synthetic aperture radar (SAR) interferometry. Here we show that SPOT images can also be used to accurately map the fault zone and to determine the slip distribution by subpixel correlation of images acquired before and after an earthquake. The measured slip includes the contribution of possible distributed shear that might not be clearly expressed in surface ruptures and smoothes out possible along-strike variability due to near-surface fault complexities. We apply the technique to the M_s = 7.4, 1999, Izmit earthquake. Our results reveal a <100-m-wide and very linear fault zone that can be traced for 70 km from G\u00f6lc\u00fck to Akyazi, along which supershear rupture has been inferred. The obtained slip distribution compares well with the field measurements and is consistent with ground deformation measured at some distance from the fault zone using SAR images. Very little deformation was accommodated off the main fault plane. Maximum slip is observed near Sapanca lake at a small fault jog that has probably influenced rupture propagation.", "doi": "10.1029/2000JB000102", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2002-04-10", "series_number": "B4", "volume": "107", "issue": "B4", "pages": "Art. No. 2062" }, { "id": "authors:ysx0c-ra407", "collection": "authors", "collection_id": "ysx0c-ra407", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120907-132803936", "type": "article", "title": "Fluid-driven seismicity in a stable tectonic context:\n The Remiremont fault zone, Vosges, France", "author": [ { "family_name": "Audin", "given_name": "Laurence", "clpid": "Audin-L" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Flouzat", "given_name": "Mireille", "clpid": "Flouzat-M" }, { "family_name": "Plantet", "given_name": "Jean-Louis", "clpid": "Plantet-J-L" } ], "abstract": "Some relocated seismic events, which have small magnitudes (ML < 4.8), are found to align along a 40 km-long fault zone flanking the southern Vosges Massif to the west. It joins to the south with the epicentral area of the historical 1682 earthquake (Io = VIII MSK). The Remiremont cluster was preceded by a period of seismic coalescence and triggered outward of bilateral seismic migration. The 1984 seismic crisis developed along a well defined 3 km-long vertical plane. In both cases, migration rates of the order of 5\u201310 km/yr over 30 km-long distances are determined. This pattern requires some mechanism of stress interaction which must act over distances of the order of 1 to 20 km within years. Given the low tectonic activity and the magnitudes of the events the stress transfer cannot result from co-seismic elastic loading or from transient strain at depth. We suggest that the seismic activity reflect rupture of asperities driven by fluid-flow in a zone of relatively high permeability.", "doi": "10.1029/2001GL012988", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2002-03-15", "series_number": "6", "volume": "29", "issue": "6", "pages": "Art. No. 1091" }, { "id": "authors:epwmb-n9v63", "collection": "authors", "collection_id": "epwmb-n9v63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-135500795", "type": "article", "title": "GPS network monitors the Western Alps' deformation over a five-year period: 1993\u20131998", "author": [ { "family_name": "Vigny", "given_name": "C.", "clpid": "Vigny-C" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The Western Alps are among the best studied collisional belts with both detailed structural mapping and also crustal geophysical investigations such as the ECORS and EGT seismic profile. By contrast, the present-day kinematics of the belt is still largely unknown due to small relative motions and the insufficient accuracy of the triangulation data. As a consequence, several tectonic problems still remain to be solved, such as the amount of N\u2013S convergence in the Occidental Alps, the repartition of the deformation between the Alpine tectonic units, and the relation between deformation and rotation across the Alpine arc. In order to address these problems, the GPS ALPES group, made up of French, Swiss and Italian research organizations, has achieved the first large-scale GPS surveys of the Western Alps. More than 60 sites were surveyed in 1993 and 1998 with a minimum observation of 3\u2009days at each site. GPS data processing has been done by three independent teams using different software. The different solutions have horizontal repeatabilities (N\u2013E) of 4\u20137\u2009mm in 1993 and 2\u20133\u2009mm in 1998 and compare at the 3\u20135-mm level in position and 2-mm/yr level in velocity. A comparison of 1993 and 1998 coordinates shows that residual velocities of the GPS marks are generally smaller than 2\u2009mm/yr, precluding a detailed tectonic interpretation of the differential motions. However, these data seem to suggest that the N\u2013S compression of the Western Alps is quite mild (less than 2\u2009mm/yr) compared to the global convergence between the African and Eurasian plate (6\u2009mm/yr). This implies that the shortening must be accomodated elsewhere by the deformation of the Maghrebids and/or by rotations of Mediterranean microplates. Also, E\u2013W velocity components analysis supports the idea that E\u2013W extension exists, as already suggested by recent structural and seismotectonic data interpretation.", "doi": "10.1007/s00190-001-0231-8", "issn": "0949-7714", "publisher": "Springer Verlag", "publication": "Journal of Geodesy", "publication_date": "2002-02", "series_number": "2", "volume": "76", "issue": "2", "pages": "63-76" }, { "id": "authors:e989m-mdz31", "collection": "authors", "collection_id": "e989m-mdz31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-080944310", "type": "article", "title": "Intracontinental subduction and Palaeozoic inheritance\n of the lithosphere suggested by a teleseismic experiment\n across the Chinese Tien Shan", "author": [ { "family_name": "Poupinet", "given_name": "G.", "clpid": "Poupinet-G" }, { "family_name": "Avouac", "given_name": "J.-Ph.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Jiang", "given_name": "M.", "clpid": "Jiang-M" }, { "family_name": "Wei", "given_name": "S.", "clpid": "Wei-Shengji" }, { "family_name": "Kissling", "given_name": "E.", "clpid": "Kissling-E" }, { "family_name": "Herquel", "given_name": "G.", "clpid": "Herquel-G" }, { "family_name": "Guilbert", "given_name": "J.", "clpid": "Guilbert-J" }, { "family_name": "Paul", "given_name": "A.", "clpid": "Paul-A" }, { "family_name": "Wittlinger", "given_name": "G.", "clpid": "Wittlinger-G" }, { "family_name": "Su", "given_name": "H.", "clpid": "Su-H" }, { "family_name": "Thomas", "given_name": "J.-C.", "clpid": "Thomas-J-C" } ], "abstract": "Teleseismic tomography across the Chinese Tien Shan shows that seismic wave speeds in the lithosphere beneath central Tien Shan are high and therefore the lithosphere is not weaker than that beneath the adjacent undeformed Tarim and Junggar basins. There is evidence for significant velocity contrasts within the lithosphere that are presumably inherited from the Palaeozoic collision history. The high-velocity, thick Yili block observed underneath the northern Tien Shan is a clue for shortening by a intracontinental subduction. The observed geometry is consistent with a simple model of intracontinental subduction and suggests that, during orogeny, the lithosphere has remained heterogeneous and has deformed along existing planes of weakness rather than by homogeneous thickening of a particularly weak lithosphere.", "doi": "10.1046/j.1365-3121.2002.00391.x", "issn": "0954-4879", "publisher": "Blackwell Publishing", "publication": "Terra Nova", "publication_date": "2002-02", "series_number": "1", "volume": "14", "issue": "1", "pages": "18-24" }, { "id": "authors:wcbqz-aye13", "collection": "authors", "collection_id": "wcbqz-aye13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120907-135223754", "type": "article", "title": "Le cycle sismique en Himalaya", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bollinger", "given_name": "Laurent", "clpid": "Bollinger-L" }, { "family_name": "Lav\u00e9", "given_name": "J\u00e9r\u00f4me", "clpid": "Lav\u00e9-J" }, { "family_name": "Cattin", "given_name": "Rodolphe", "clpid": "Cattin-R" }, { "family_name": "Flouzat", "given_name": "Mireille", "clpid": "Flouzat-M" } ], "abstract": "We discuss the seismic cycle in the Himalayas and its relation to mountain building on the basis of geodetic, seismological and geological data collected in the Himalaya of Nepal. On average over several seismic cycles, localized slip on a major thrust fault, the Main Himalayan Thrust fault, MHT, accommodates the \u223c21 mm\u00b7yr^(\u22121) convergence rate between southern Tibet and India. The geodetic data show that the MHT is presently locked from the sub-Himalayas to beneath the front of the high range where it roots into a sub-horizontal ductile shear zone under southern Tibet. Aseismic slip during the interseismic period induces stress accumulation at the southern edge of this shear zone triggering intense microseismic activity and elastic straining of the upper crust at the front of the high range. This deformation is released, on the long term, by major earthquakes on the MHT. Such an event is the M_w 8.4-1934-earthquake that ruptured a 250\u2013300-km long segment. The major seismic events along the Himalayas since the 19th century have released more than 70% of the crustal strain accumulated over that period, suggesting that, if any, aseismic slip on the MHT cannot account for more than 30% of the total slip.", "doi": "10.1016/S1251-8050(01)01573-7", "issn": "1251-8050", "publisher": "Elsevier", "publication": "Comptes Rendus de l'Acad\u00e9mie des Sciences Series IIA Earth and Planetary Science", "publication_date": "2001-11-15", "series_number": "9", "volume": "333", "issue": "9", "pages": "513-529" }, { "id": "authors:t94xt-aed05", "collection": "authors", "collection_id": "t94xt-aed05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-144906378", "type": "article", "title": "Fluvial incision and tectonic uplift across the Himalayas of central Nepal", "author": [ { "family_name": "Lav\u00e9", "given_name": "J.", "clpid": "Lav\u00e9-J" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The pattern of fluvial incision across the Himalayas of central Nepal is estimated from the distribution of Holocene and Pleistocene terraces and from the geometry of modern channels along major rivers draining across the range. The terraces provide good constraints on incision rates across the Himalayan frontal folds (Sub-Himalaya or Siwaliks Hills) where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces. Farther north and upstream, in the Lesser Himalaya, prominent fill terraces were deposited, probably during the late Pleistocene, and were subsequently incised. The amount of bedrock incision beneath the fill deposits is generally small, suggesting a slow rate of fluvial incision in the Lesser Himalaya. The terrace record is lost in the high range where the rivers are cutting steep gorges. To complement the terrace study, fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate. This approach allows quantification of the effect of variations in channel slope, width, and discharge on the incision rate of a river; the determination of incision rates requires an additional lithological calibration. The two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared. In the Sub-Himalaya, river incision is rapid, with values up to 10\u201315 mm/yr. It does not exceed a few millimeters per year in the Lesser Himalaya, and rises abruptly at the front of the high range to reach values of \u223c4\u20138 mm/yr within a 50-km-wide zone that coincides with the position of the highest Himalayan peaks. Sediment yield derived from the measurement of suspended load in Himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range. The observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat-ramp-flat geometry of the Main Himalayan Thrust fault. The morphology of the range reflects a dynamic equilibrium between present-day tectonics and surface processes. The sharp relief together with the high uplift rates in the Higher Himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the Tibetan Plateau driven by late Cenozoic climate change, or late Miocene reactivation of the Main Central Thrust.", "doi": "10.1029/2001JB000359", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2001-11-10", "series_number": "B11", "volume": "106", "issue": "B11", "pages": "26561-26591" }, { "id": "authors:072e1-vmf58", "collection": "authors", "collection_id": "072e1-vmf58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120918-065730339", "type": "article", "title": "Mouvement post-messinien sur la faille de N\u00eemes; implications pour la sismotectonique de la Provence", "author": [ { "family_name": "Schlupp", "given_name": "Antoine", "clpid": "Schlupp-A" }, { "family_name": "Clauzon", "given_name": "Georges", "clpid": "Clauzon-G" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The seismicity of southern France probably results from the convergence between Africa and Europe which proceeds at a rate of approximately 0,8 cm/year at the Provence longitude [Nuvell-DeMets et al., 1990]. The potentially active faults delimit a large panel in the Mesozoic cover. It includes E-W compressive structures (Mont-Ventoux, Montagne de Lure to the north, Luberon, Costes et Trevaresse to the south) and NE left-lateral strike slip (Durance to the east and Nimes, to the west, and possibly the Cevennes Fault) [e.g., Grellet et al., 1993; Sebrier et al., 1997; Lacassin et al., 1998]. The Nimes Fault, which is considered as one of the main faults of southeastern France [Combes, 1984; Grellet et al., 1993; Ghafiri, 1995] is associated with only few and small seismic events, but paleoseismic evidence for larger earthquakes, with magnitudes possibly as large as 6.5, were found on a subsidiary fault near Courthezon [Combes et al., 1993]. Here, we try to quantify fault activity over a longer period of time than that accessible from the usual geomorphic approach, by assessing possible displacement of Messinian markers on the Nimes fault. In the early Miocene a regional erosion surface of Burdigalian age (around-20 Ma) was formed. This surface is still preserved and has not been much deformed west of the Nimes fault. To the east, this surface is only gently folded due to E-W anticlines [Champion, 1999; Champion et al., 2000]. This contrast suggests that the Nimes fault has been active and has accommodated N-S shortening after the abandonment of the Burdigalian erosion surface. The Nimes and Pujaut faults can be followed in the topography between Nimes and Sauveterre where they are generally bounded by outcrops of Mesozoic limestone (fig. 2A-3). To the NE, the Nimes fault can be roughly traced across the Quaternary Rhone alluvium, between Sauveterre and the Mont Ventoux. It is marked by disruption of the continuity of the terrasses of Chateauneuf-du-Pape. The signal is only tenuous and cannot be used to infer precisely the fault location and segmentation but suggests that the faults have been active during the Quaternary. During the Messinian, starting at about -5.95 Ma, the Mediterranean sea level fell by about 1500 m [Clauzon, 1975; Krijgsman et al., 1999; Gautier et al., 1994; Cande et Kent, 1992-1995; Clauzon et al., 1995]. The major tributaries were forced to cut down and formed deep and narrow valleys. The Mediterranean sea rose up to an elevation of +80 m NGF at -5.32 Ma, flooding the canyons, and remained stable until about -3.8 Ma [Vail and Mitchum, 1979; Benson et al., 1991; Cita, 1975; Haq et al., 1987; Hilgen et Langeries, 1993]. After -5.32 Ma the canyons were filled with Pliocene sediments. The canyon formed by the Rhone incision during the Messinian crisis is well documented [Clauzon, 1982; Clauzon et al., 1995; Clauzon et al., 1999; Rubino et al., 2000]. We found evidence for a tributary canyon on an old seismic line ELF M2S8. The canyon strikes E-W between the \"Barre de Roquemaure\" and \"Barre de Caderache\" and should cross the Nimes Fault. In order to constrain more tightly its geometry near the Nimes Fault, we have implemented three seismic lines. If we trace the position of the southern border of the canyon using the different profiles and the surface geology, we find that the horizontal offset at the fault cannot be much larger than about 500 meters. In order to image a possible smaller offset we have determined the geometry of the canyon from a microseismic zoning technique [Nakamura, 1989; Duval et al., 1997; Ibs-von Seht M. and Wholenberg, 1999; Sabourault, 1999]. Measurements were conducted at 37 points which were used in complement. The depth to the canyon bottom was determined using the velocities derived from the seismic profiles and was cross-checked from the comparison with geological log at points F1 and F2. The geometry of the southern edge of the Messinian canyon, shows a left-lateral offset of 440 m + or -50 m, which might be taken to reflect post-Messinian fault motion. Assuming that the observed 440 m offset of the Messinian canyon at the Nimes fault is due to fault motion, and that the fault slip rate has not varied significantly since the Messinian crisis, we derive a left-lateral slip rate of 0.06 to 0.09 mm/year. Given that the observed deflection of the flank of the canyon might in part be of non tectonic origin, our study basically places an upper limit of 0.09 mm/yr on the slip rate on the Nimes faults. Such a low slip rate is comparable with estimates obtained on the Durance Fault [Baroux, 2000] and on the E-W folds and thrust faults east of the Nimes faults such as Ventoux-Lure and Alpilles-Costes-Trevaresse [Champion, 1999; Champion et al., 2000]. Although the details of the kinematics scheme of active deformation of Provence remain a matter of discussion, these various faults are probably linked and must have similar slip rates.", "doi": "10.2113/172.6.697", "issn": "0037-9409", "publisher": "Soci\u00e9t\u00e9 G\u00e9ologique de France", "publication": "Bulletin de la Soci\u00e9t\u00e9 G\u00e9ologique de France", "publication_date": "2001-11", "series_number": "6", "volume": "172", "issue": "6", "pages": "697-711" }, { "id": "authors:0gtt7-hwf77", "collection": "authors", "collection_id": "0gtt7-hwf77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-084809471", "type": "article", "title": "Gravity anomalies, crustal structure and thermo-mechanical support of the Himalaya of Central Nepal", "author": [ { "family_name": "Cattin", "given_name": "R.", "clpid": "Cattin-R" }, { "family_name": "Martelet", "given_name": "G.", "clpid": "Martelet-G" }, { "family_name": "Henry", "given_name": "P.", "clpid": "Henry-P" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Diament", "given_name": "M.", "clpid": "Diament-M" }, { "family_name": "Shakya", "given_name": "T. R.", "clpid": "Shakya-T-R" } ], "abstract": "We use two gravity profiles that we measured across Central Nepal, in conjunction with existing data, to constrain the mechanical behaviour and the petrological structure of the lithosphere in the Himalayan collision zone. The data show (1) overcompensation of the foreland and undercompensation of the Higher Himalaya, as expected from the flexural support of the range; (2) a steep gravity gradient of the order of 1.3 mgal km^(\u22121) beneath the Higher Himalaya, suggesting a locally steeper Moho; and (3) a 10 km wide hinge in southern Tibet. We compare these data with a 2-D mechanical model in which the Indian lithosphere is flexed down by the advancing front of the range and sedimentation in the foreland. The model assumes brittle Coulomb failure and non-linear ductile flow that depends on local temperature, which is computed from a steady-state thermal model. The computed Moho fits seismological constraints and is consistent with the main trends in the observed Bouguer anomaly. It predicts an equivalent elastic thickness of 40\u201350 km in the foreland. The flexural rigidity decreases northwards due to thermal and flexural weakening, resulting in a steeper Moho dip beneath the high range. Residuals at short wavelengths (over distances of 20\u201330 km) are interpreted in terms of (1) sediment compaction in the foreland (\u0394\u03c1 = 150 kg m^(\u22123) between the Lower and Middle Siwaliks); (2) the contact between the Tertiary molasse and the meta-sediments of the Lesser Himalaya at the MBT (\u0394\u03c1 = 220 kg m^(\u22123)); and (3) the Palung granite intrusion in the Lesser Himalaya (\u0394\u03c1 = 80 kg m^(\u22123)). Finally, if petrological transformations expected from the local (P, T) are assumed, a gravity signature of the order of 250 mgal is predicted north of the Lesser Himalaya, essentially due to eclogitization of the lower crust, which is inconsistent with the gravity data. We conclude that eclogitization of the Indian crust does not take place as expected from a steady-state local equilibrium assumption. We show, however, that eclogitization might actually occur beneath southern Tibet, where it could explain the hinge observed in the gravity data. We suspect that these eclogites are subducted with the Indian lithosphere.", "doi": "10.1046/j.0956-540x.2001.01541.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2001-11", "series_number": "2", "volume": "147", "issue": "2", "pages": "381-392" }, { "id": "authors:m6z9q-a8a79", "collection": "authors", "collection_id": "m6z9q-a8a79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-133723809", "type": "article", "title": "On the use of dislocations to model interseismic strain and stress build-up at intracontinental thrust faults", "author": [ { "family_name": "Vergne", "given_name": "J.", "clpid": "Vergne-J" }, { "family_name": "Cattin", "given_name": "R.", "clpid": "Cattin-R" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Creeping dislocations in an elastic half-space are commonly used to model interseismic deformation at subduction zones, and might also apply to major intracontinental thrust faults such as the Main Himalayan Thrust. Here, we compare such models with a more realistic 2-D finite element model that accounts for the mechanical layering of the continental lithosphere and surface processes, and that was found to fit all available constraints on interseismic and long-term surface displacements. These can also be fitted satisfactorily from dislocation models. The conventional back-slip model, commonly used for subduction zones, may, however, lead to a biased inference about the geometry of the locked portion of the thrust fault. We therefore favour the use of a creeping buried dislocation that simulates the ductile shear zone in the lower crust. A limitation of dislocation models is that the mechanical response of the lithosphere to the growth of the topography by bending of the elastic cores and ductile flow in the lower crust cannot be easily introduced. Fortunately these effects can be neglected because we may assume, to first order, a stationary topography. Moreover, we show that not only can dislocation models be used to adjust surface displacements but, with some caution, they can also provide a physically sound rationale to interpret interseismic microseismicity in terms of stress variations.", "doi": "10.1046/j.1365-246X.2001.00524.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2001-10", "series_number": "1", "volume": "147", "issue": "1", "pages": "155-162" }, { "id": "authors:9d50b-e8q22", "collection": "authors", "collection_id": "9d50b-e8q22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-092913349", "type": "article", "title": "Co-seismic deformation during the M_w 7.3 Aqaba earthquake (1995) from ERS-SAR interferometry", "author": [ { "family_name": "Klinger", "given_name": "Yann", "clpid": "Klinger-Y" }, { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The M_w 7.3 1995 Aqaba earthquake is the largest instrumental earthquake along the Dead Sea Fault. We complement previous seismological studies by analyzing co\u2010seismic ground displacement from differential interferometry computed from ERS images spanning 3 different areas. They are compared with a synthetic model derived from seismological study. Only far\u2010field deformation related to the main sub\u2010event could be revealed because the near\u2010field area lies within the gulf. The interferometric data imply a 56 km long and 10 km wide fault segment, connecting the Elat Deep to the Aragonese Deep, which strikes N195\u00b0E and dips 65\u00b0 to the west, with 2.1 m left\u2010lateral slip and a 15.5\u00b0 rake indicating a slight normal component. The geodetic moment compares well with the seismic moment", "doi": "10.1029/1999GL008463", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2000-11-15", "series_number": "22", "volume": "27", "issue": "22", "pages": "3651-3654" }, { "id": "authors:668zb-gd602", "collection": "authors", "collection_id": "668zb-gd602", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120912-085441127", "type": "article", "title": "Slip rate on the Dead Sea transform fault in northern Araba valley (Jordan)", "author": [ { "family_name": "Klinger", "given_name": "Y.", "clpid": "Klinger-Y" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Karaki", "given_name": "N. Abou", "clpid": "Karaki-N-A" }, { "family_name": "Dorbath", "given_name": "L.", "clpid": "Dorbath-L" }, { "family_name": "Bourles", "given_name": "D.", "clpid": "Bourles-D" }, { "family_name": "Reyss", "given_name": "J. L.", "clpid": "Reyss-J-L" } ], "abstract": "The Araba valley lies between the southern tip of the Dead Sea and the Gulf of Aqaba. This depression, blanketed with alluvial and lacustrine deposits, is cut along its entire length by the Dead Sea fault. In many places the fault is well defined by scarps, and evidence for left-lateral strike-slip faulting is abundant. The slip rate on the fault can be constrained from dated geomorphic features displaced by the fault. A large fan at the mouth of Wadi Dahal has been displaced by about 500 m since the bulk of the fanglomerates were deposited 77\u2013140 kyr ago, as dated from cosmogenic isotope analysis (^(10)Be in chert) of pebbles collected on the fan surface and from the age of transgressive lacustrine sediments capping the fan. Holocene alluvial surfaces are also clearly offset. By correlation with similar surfaces along the Dead Sea lake margin, we propose a chronology for their emplacement. Taken together, our observations suggest an average slip rate over the Late Pleistocene of between 2 and 6 mm yr^(\u22121), with a preferred value of 4 mm yr^(\u22121). This slip rate is shown to be consistent with other constraints on the kinematics of the Arabian plate, assuming a rotation rate of about 0.396\u00b0 Myr^(\u22121) around a pole at 31.1\u00b0N, 26.7\u00b0E relative to Africa.", "doi": "10.1046/j.1365-246x.2000.00165.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2000-09", "series_number": "3", "volume": "142", "issue": "3", "pages": "755-768" }, { "id": "authors:yych0-3ma07", "collection": "authors", "collection_id": "yych0-3ma07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120918-115149427", "type": "article", "title": "Seismic behaviour of the Dead Sea fault along Araba valley, Jordan", "author": [ { "family_name": "Klinger", "given_name": "Y.", "clpid": "Klinger-Y" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Dorbath", "given_name": "L.", "clpid": "Dorbath-L" }, { "family_name": "Karaki", "given_name": "N. Abou", "clpid": "Karaki-N-A" }, { "family_name": "Tisnerat", "given_name": "N.", "clpid": "Tisnerat-N" } ], "abstract": "The Dead Sea fault zone is a major left-lateral strike-slip fault. South of the Dead Sea basin, the Wadi Araba fault extends over 160 km to the Gulf of Aqaba. The Dead Sea fault zone is known to have produced several relatively large historical earthquakes. However, the historical events are unequally distributed along the fault and only four events have been reported in the Araba valley over the last few thousands of years. Magnitudes estimated from the historical record are probably slightly smaller than that of the M_w \u223c 7.3 earthquake that struck the Gulf of Aqaba in 1995. The fault cuts straight across Pleistocene to Holocene alluvium and shows morphologic evidence for essentially pure strike-slip motion. Regional seismic monitoring reveals little microseismicity along the fault except around the Dead Sea and Gulf of Aqaba, where the fault splays into complex pull-apart basin fault systems. We have investigated the fault zone at several sites selected from SPOT images and the study of aerial photography. At the site of the now destroyed Tilah Castle, a well-preserved wall, dated to be about 1200 yr BP (^(14)C age on charcoal), is cut by the fault and offset by 2.2 m. Comparison with offset gullies at a nearby site 3 km to the north and at three other sites, respectively 25, 50 and 65 km to the south, reveals that this specific fault displacement is probably related to the last seismic event that ruptured that fault segment, possibly in AD 1458.\n\nMoreover, the offset gullies suggest a characteristic slip behaviour with recurring slip of about 1.5 m on average. Given the 4 \u00b1 2 mm yr^(\u22121) slip rate derived for this fault segment, we infer that the fault should produce M_w \u223c 7 earthquakes along some segment in the Araba valley about every 200 years. The historical period, with only four well-documented large earthquakes in AD 1068, AD 1212, AD 1293 and AD 1458, thus appears to have been relatively quiescent, with a 20 per cent deficit of M_w \u223c 7 earthquakes. However, our data do not exclude the possibility of larger M_w \u223c 7.6 earthquakes or time clustering of earthquakes over longer timespans. An alternative seismic behaviour involves M_w \u223c 7.6 earthquakes about every 6000 years and M_w \u223c 7 earthquakes about every 250 years. The historical catalogue would then appear to be complete for M_w \u223c 7 earthquakes.", "doi": "10.1046/j.1365-246x.2000.00166.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2000-09", "series_number": "3", "volume": "142", "issue": "3", "pages": "769-782" }, { "id": "authors:msqmh-e2w24", "collection": "authors", "collection_id": "msqmh-e2w24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PUYao00", "type": "article", "title": "Measuring Earthquakes from Optical Satellite Images", "author": [ { "family_name": "Van Puymbroeck", "given_name": "Nad\u00e8ge", "clpid": "Van-Puymbroeck-N" }, { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Binet", "given_name": "Renaud", "clpid": "Binet-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Taboury", "given_name": "Jean", "clpid": "Taboury-J" } ], "abstract": "Syst\u00e8me pour l'Observation de la Terre images are used to map ground displacements induced by earthquakes. Deformations (offsets) induced by stereoscopic effect and roll, pitch, and yaw of satellite and detector artifacts are estimated and compensated. Images are then resampled in a cartographic projection with a low-bias interpolator. A subpixel correlator in the Fourier domain provides two-dimensional offset maps with independent measurements approximately every 160 m. Biases on offsets are compensated from calibration. High-frequency noise (0.125 m^-1 ) is ~0.01 pixels. Low-frequency noise (lower than 0.001 m^-1 ) exceeds 0.2 pixels and is partially compensated from modeling. Applied to the Landers earthquake, measurements show the fault with an accuracy of a few tens of meters and yields displacement on the fault with an accuracy of better than 20 cm. Comparison with a model derived from geodetic data shows that offsets bring new insights into the faulting process.", "issn": "0003-6935", "publisher": "Optical Society of America", "publication": "Applied Optics", "publication_date": "2000-07-10", "series_number": "20", "volume": "39", "issue": "20", "pages": "3486-3494" }, { "id": "authors:jx2a4-enc48", "collection": "authors", "collection_id": "jx2a4-enc48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120907-133541924", "type": "article", "title": "Modeling mountain building and the seismic cycle in the Himalaya of Nepal", "author": [ { "family_name": "Cattin", "given_name": "R.", "clpid": "Cattin-R" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "A host of information is now available regarding the geological and thermal structure as well as deformation rate across the Himalaya of central Nepal. These data are reconciled in a two-dimensional mechanical model that incorporates the rheological layering of the crust which depends on the local temperature and surface processes. Over geological timescale (5 Ma) the \u223c20 mm/yr estimated shortening rate across the range is accommodated by localized thrust faulting along the Main Himalayan Thrust fault (MHT). The MHT reaches the surface along the foothills, where it is called the Main Frontal Thrust fault (MFT). The MHT flattens beneath the Lesser Himalaya and forms a midcrustal ramp at the front of the Higher Himalaya, consistent with the river incision and the anticlinal structure of the Lesser Himalaya. Farther northward the MHT roots into a subhorizontal shear zone that coincides with a midcrustal seismic reflector. Aseismic slip along this shear zone is accommodated in the interseismic period by elastic straining of the upper crust, increasing the Coulomb stress beneath the front of the Higher Himalaya, where most of the microseismic activity clusters. Negligible deformation of the hanging wall requires a low apparent friction coefficient (\u03bc) less than \u223c0.3 on the flat portion of the MHT. On the ramp, \u03bc might be as high as 0.6. Sensitivity tests show that a rather compliant, quartz-rich rheology and a high radioactive heat production in the upper crust of \u223c2.5 \u03bcW/m^3 is required. Erosion affects the thermal structure and interplays with crustal deformation. A dynamic equilibrium is obtained in which erosion balances tectonic uplift maintaining steady state thermal structure, topography, and deformation field. Using a linear diffusion model of erosion, we constrain the value of the mass diffusivity coefficient to 0.5\u20131.6\u00d7l0^4 m^2/yr. This study demonstrates that the data are internally consistent and compatible with current understanding of the mechanics of crustal deformation and highlight the role of viscous flow in the lower crust and of surface erosion in orogeny processes on the long term as well as during interseismic period.", "doi": "10.1029/2000JB900032", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2000-06-10", "series_number": "B6", "volume": "105", "issue": "B6", "pages": "13389-13407" }, { "id": "authors:09669-s9c06", "collection": "authors", "collection_id": "09669-s9c06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120906-154655223", "type": "article", "title": "Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal", "author": [ { "family_name": "Lav\u00e9", "given_name": "J.", "clpid": "Lav\u00e9-J" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We analyze geomorphic evidence of recent crustal deformation in the sub-Himalaya of central Nepal, south of the Kathmandu Basin. The Main Frontal Thrust fault (MFT), which marks the southern edge of the sub-Himalayan fold belt, is the only active structure in that area. Active fault bend folding at the MFT is quantified from structural geology and fluvial terraces along the Bagmati and Bakeya Rivers. Two major and two minor strath terraces are recognized and dated to be 9.2, 2.2, and 6.2, 3.7 calibrated (cal) kyr old, respectively. Rock uplift of up to 1.5 cm/yr is derived from river incision, accounting for sedimentation in the Gangetic plain and channel geometry changes. Rock uplift profiles are found to correlate with bedding dip angles, as expected in fault bend folding. It implies that thrusting along the MFT has absorbed 21 \u00b1 1.5 mm/yr of N-S shortening on average over the Holocene period. The \u00b11.5 mm/yr defines the 68% confidence interval and accounts for uncertainties in age, elevation measurements, initial geometry of the deformed terraces, and seismic cycle. At the longitude of Kathmandu, localized thrusting along the Main Frontal Thrust fault must absorb most of the shortening across the Himalaya. By contrast, microseismicity and geodetic monitoring over the last decade suggest that interseismic strain is accumulating beneath the High Himalaya, 50\u2013100 km north of the active fold zone, where the Main Himalayan Thrust (MHT) fault roots into a ductile d\u00e9collement beneath southern Tibet. In the interseismic period the MHT is locked, and elastic deformation accumulates until being released by large (M_w > 8) earthquakes. These earthquakes break the MHT up to the near surface at the front of the Himalayan foothills and result in incremental activation of the MFT.", "doi": "10.1029/1999JB900292", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2000-03-10", "series_number": "B3", "volume": "105", "issue": "B3", "pages": "5735-5770" }, { "id": "authors:tjh0a-pfr75", "collection": "authors", "collection_id": "tjh0a-pfr75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-135523937", "type": "article", "title": "Electrical structure of the Himalaya of Central Nepal: high conductivity around the mid-crustal ramp along the MHT", "author": [ { "family_name": "Lemonnier", "given_name": "Carole", "clpid": "Lemonnier-C" }, { "family_name": "Marquis", "given_name": "Guy", "clpid": "Marquis-G" }, { "family_name": "Perrier", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Perrier-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Chitrakar", "given_name": "Gyani", "clpid": "Chitrakar-G" }, { "family_name": "Kafle", "given_name": "Basantha", "clpid": "Kafle-B" }, { "family_name": "Sapkota", "given_name": "Som", "clpid": "Sapkota-S" }, { "family_name": "Gautam", "given_name": "Umesh", "clpid": "Gautam-U" }, { "family_name": "Tiwari", "given_name": "Dilliram", "clpid": "Tiwari-D" }, { "family_name": "Bano", "given_name": "Maksim", "clpid": "Bano-M" } ], "abstract": "Twelve broadband magnetotelluric (MT) soundings were performed across the Himalaya of Central Nepal in 1996 in order to determine the electrical structure of the crust and its relation to geological structures and active tectonics. The MT impedance tensors were obtained for frequencies between 0.001 and 500 Hz. The 2\u2010D section, derived from joint inversion of TE\u2010 and TM mode after RRI and Groom/Bailey decomposition, shows high conductivity in the foreland basin (\u223c30 \u03a9.m) that contrasts with the resistive Indian basement (>300 \u03a9.m) and Lesser Himalaya (>1000 \u03a9.m). In addition, our MT sounding reveals a major conductive feature beneath the front of the Higher Himalaya, also characterized by intense microseismic activity, and the position of a mid\u2010crustal ramp along the major active thrust fault (MHT). This high conductivity zone probably reflects metamorphic fluids, released during underthrusting of the Indian basement and pervading well connected microcracks induced by interseismic stress build\u2010up, or distributed brittle deformation around the ramp.", "doi": "10.1029/1999GL008363", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1999-11-01", "series_number": "21", "volume": "26", "issue": "21", "pages": "3261-3264" }, { "id": "authors:t67sc-2bj41", "collection": "authors", "collection_id": "t67sc-2bj41", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120907-152149864", "type": "article", "title": "Measuring near field coseismic displacements from SAR images: Application to the Landers Earthquake", "author": [ { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Taboury", "given_name": "Jean", "clpid": "Taboury-J" } ], "abstract": "We describe a procedure to compute SAR interferograms based on the compensation of the images' mis\u2010registrations due to the ground deformation and on a specific adaptive filtering to improve the SNR in the measurement where displacement gradients are large. Applied to the Landers earthquake case, the registration reduces the phase noise by 20\u00b0 (rms) near the fault and the interferogram reveals fringes that would not show out otherwise. The interferogram is validated by comparison, in the far field, with a GPS/EDM\u2010based model. The inferred displacement field shows discontinuities that follow the fault within few hundred meters. Close to the fault the measured displacements differ significantly from that predicted by elastic modeling of the far\u2010field data. Interferometry and measurements derived from the images' amplitude (offsets) appear to be complementary techniques providing original measurements that may help to reconcile seismological and geodetic models of coseismic deformation with measurements of fault\u2010slip at the surface.", "doi": "10.1029/1999GL900524", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1999-10-01", "series_number": "19", "volume": "26", "issue": "19", "pages": "3017-3020" }, { "id": "authors:p4hmt-cyv64", "collection": "authors", "collection_id": "p4hmt-cyv64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-150647769", "type": "article", "title": "Seismotectonics of the Nepal Himalaya from a local seismic network", "author": [ { "family_name": "Pandey", "given_name": "M. R.", "clpid": "Pandey-M-R" }, { "family_name": "Tanduka", "given_name": "R. P.", "clpid": "Tanduka-R-P" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Vergne", "given_name": "J.", "clpid": "Vergne-J" }, { "family_name": "H\u00e9ritier", "given_name": "Th.", "clpid": "H\u00e9ritier-Th" } ], "abstract": "The National Seismological Network of Nepal consists of 17 short period seismic stations operated since 1994. It provides an exceptional view of the microseismic activity over nearly one third of the Himalayan arc, including the only segment, between longitudes 78\u00b0E and 85\u00b0E, that has not produced any M>8 earthquakes over the last century. It shows a belt of seismicity that follows approximately the front of the Higher Himalaya with most of the seismic moment being released at depths between 10 and 20 km. This belt of seismicity is interpreted to reflect interseismic stress accumulation in the upper crust associated with creep in the lower crust beneath the Higher Himalaya. The seismic activity is more intense around 82\u00b0E in Far-Western Nepal and around 87\u00b0E in Eastern Nepal. Western Nepal, between 82.5 and 85\u00b0E, is characterized by a particularly low level of seismic activity. We propose that these lateral variations are related to segmentation of the Main Himalayan Thrust Fault. The major junctions between the different segments would thus lie at about 87\u00b0E and 82\u00b0E with possibly an intermediate one at about 85\u00b0E. These junctions seem to coincide with some of the active normal faults in Southern Tibet. Lateral variation of seismic activity is also found to correlate with lateral variations of geological structures suggesting that segmentation is a long-lived feature. We infer four 250\u2013400 km long segments that could produce earthquakes comparable to the M=8.4 Bihar\u2013Nepal earthquake that struck eastern Nepal in 1934. Assuming the model of the characteristic earthquake, the recurrence interval between two such earthquakes on a given segment is between 130 and 260 years.", "doi": "10.1016/S1367-9120(99)00034-6", "issn": "1367-9120", "publisher": "Elsevier", "publication": "Journal of Asian Earth Sciences", "publication_date": "1999-10", "series_number": "5-6", "volume": "17", "issue": "5-6", "pages": "703-712" }, { "id": "authors:v18t1-v3906", "collection": "authors", "collection_id": "v18t1-v3906", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-104113980", "type": "article", "title": "Streaming potential measurements 1. Properties of the electrical double layer from crushed rock samples", "author": [ { "family_name": "Lorne", "given_name": "Benoit", "clpid": "Lorne-B" }, { "family_name": "Perrier", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Perrier-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The \u03be potential has been inferred from streaming potential measurements with crushed rock samples as a function of pH and electrolyte concentration for various salts. The value obtained for crushed Fontainebleau sandstone at pH = 5.7 and a KCl solution with a resistivity of 400 \u03a9 m is \u221240 \u00b1 5 mV, where the error is dominated by sample to sample variations. The sensitivity of the \u03be potential to the electrolyte resistivity for KCl is given experimentally by \u03c1_f^(0.23\u00b10.014) where \u03c1_f is the electrolyte resistivity. The point of zero charge (pzc) is observed for pH = 2.5 \u00b1 0.1, and the \u03be potential is positive for pH < pzc and negative for pH > pzc. For pH > 5 the variations of the \u03be potential with pH can be approximated by \u03be(pH)/\u03be(5.7) = 1 + (0.068 \u00b1 0.004)(pH - 5.7) for \u03c1_f = 100 \u03a9 m. The \u03be potential has been observed to be sensitive to the valence of the ions and is approximately reduced by the charge of the cation, unless specific adsorption takes place like in the case of Al^3+. The experimental results are well accounted for by a three-layer numerical model of the electrical double layer, and the parameters of this model can be evaluated from the experimental data. The sensitivity of the \u03be potential to the rock minerals has also been studied. The \u03be potential obtained for granitic rocks is comparable to that obtained for Fontainebleau sandstone but can be reduced by a factor of 2\u20134 for sandstones containing significant fractions of carbonates or clay. To take into account the effect of the chemical composition of the electrolyte, a chemical efficiency is defined as the ratio of the \u03be potential to the \u03be potential measured for KCl. This chemical efficiency is measured to be \u223c80% for typical groundwater but can be as low as 40% for a water with a high dissolved carbonate content. The set of empirical laws derived from our measurements can be used to assess the magnitude of the streaming potentials expected in natural geophysical systems.", "doi": "10.1029/1999JB900156", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1999-08-10", "series_number": "B8", "volume": "104", "issue": "B8", "pages": "857-877" }, { "id": "authors:qnc58-rv860", "collection": "authors", "collection_id": "qnc58-rv860", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120914-082754709", "type": "article", "title": "Streaming potential measurements 2. Relationship between electrical and hydraulic flow patterns from rock samples during deformation", "author": [ { "family_name": "Lorne", "given_name": "Benoit", "clpid": "Lorne-B" }, { "family_name": "Perrier", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Perrier-F" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Streaming potential and resistivity measurements have been performed on Fontainebleau sandstone and Villejust quartzite samples in a triaxial device during compaction, uniaxial compression, and rupture. Measurements on individual samples do not show any clear intrinsic dependence of the streaming potential coefficient with permeability. An apparent dependence of the streaming potential coefficient with permeability is, however, observed during deformation. The effect of surface conductivity is taken into account and is small compared with the observed changes in the streaming potential coefficient. The observed dependence is therefore interpreted in terms of a difference in the evolution of the electrical and hydraulic connectivity patterns during deformation. This effect causes the streaming potential coefficient, and consequently the inferred \u03be potential, to be reduced by a geometrical factor R_G representing the electrical efficiency of the hydraulic network. Estimates of the R_G factor varying between 0.2 and 0.8 for electrolyte resistivity larger than 100 \u03a9m are obtained by comparing the values of the \u03be potential inferred from intact rock samples with the values obtained from crushed rock samples, where the geometrical effects are assumed to be negligible. The reduction of the streaming potential coefficient observed during compaction or uniaxial compression suggests that the tortuosity of the hydraulic network increases faster than the tortuosity of the electrical network. Before rupture, an increase in the streaming potential coefficient associated with the onset of dilatancy was observed for three samples of Fontainebleau sandstone and one sample of Villejust quartzite. The changes in streaming potential coefficient prior to failure range from 30% to 50%. During one experiment, an increase in the concentration of sulfate ions was also observed before failure. These experiments suggest that observable streaming potential and geochemical variations could occur before earthquakes.", "doi": "10.1029/1999JB900155", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1999-08-10", "series_number": "B8", "volume": "104", "issue": "B8", "pages": "17879-17896" }, { "id": "authors:vj4e4-jwj36", "collection": "authors", "collection_id": "vj4e4-jwj36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-112201921", "type": "article", "title": "Oblique Convergence in the Himalayas of Western Nepal Deduced from Preliminary Results of GPS Measurements", "author": [ { "family_name": "Jouanne", "given_name": "F.", "clpid": "Jouanne-F" }, { "family_name": "Mugnier", "given_name": "J. L.", "clpid": "Mugnier-J-L" }, { "family_name": "Pandey", "given_name": "M. R.", "clpid": "Pandey-M-R" }, { "family_name": "Gamond", "given_name": "J. F.", "clpid": "Gamond-J-F" }, { "family_name": "Le Fort", "given_name": "P.", "clpid": "Le-Fort-P" }, { "family_name": "Serrurier", "given_name": "L.", "clpid": "Serrurier-L" }, { "family_name": "Vigny", "given_name": "C.", "clpid": "Vigny-C" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "literal": "Idylhim Members" } ], "abstract": "A GPS network consisting of 29 sites was installed in central and western Nepal, with measurements taken in 1995 and partial remeasurements in 1997. Data suggest 15 +/\u22125 mm/yr of N180\u00b0 convergence between the Higher Himalayas and India, a result that is consistent with N\u2010S shortening across the arcuate shape of the Nepalese Himalayas and an oblique underthrusting of the Indian crust below the High Himalayas of western Nepal. A 4 +/\u22123 mm/year E\u2010W extension and deviation of the principal shortening axes are inferred east of 83\u00b0E, where Quaternary faults (Darma\u2010Bari Gad fault system and Thakkhola graben) delineate a crustal wedge. This wedge is located on the SE projection of the Karakorum fault and may segment the Himalayan thrust belt. The convergence between the outer belt of western Nepal and India is less than 3 mm/yr, an attenuation consistent with creep on a dislocation locked beneath the Lesser Himalayas. A preliminary model suggests that this N 120\u00b0E striking dislocation is affected by a 19 mm/yr thrust component and a 7 mm/yr right lateral component.", "doi": "10.1029/1999GL900416", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1999-07-01", "series_number": "13", "volume": "26", "issue": "13", "pages": "1933-1936" }, { "id": "authors:nm3ja-9nq61", "collection": "authors", "collection_id": "nm3ja-9nq61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-090724701", "type": "article", "title": "Investigation of the relationships between basin morphology,\n tectonic uplift, and denudation from the study of an active\n fold belt in the Siwalik Hills, central Nepal", "author": [ { "family_name": "Hurtrez", "given_name": "J.-E.", "clpid": "Hurtrez-J-E" }, { "family_name": "Lucazeau", "given_name": "F.", "clpid": "Lucazeau-F" }, { "family_name": "Lav\u00e9", "given_name": "J.", "clpid": "Lav\u00e9-J" }, { "family_name": "Avouac", "given_name": "J.-P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "The present study investigates correlations between an extensive range of geomorphic properties that can be estimated from a digital elevation model and the uplift rate on geological timescales. The analysis focuses on an area in the Siwalik Hills (central Nepal), where lithology and climate can be considered as uniform. This area undergoes rapid tectonic uplift at rates of up to 15 mm yr^(\u22121), which are derived from the geometric pattern of a fault-bend model of fold growth. The selected geomorphic properties can be divided in two categories, depending on whether or not the vertical dimension is taken into account. None of the planar properties are significantly correlated to uplift rate, unlike those that include the vertical dimension, such as the mean elevation of basins, hypsometric curve, and hypsometric integral, and relief defined by the amplitude factor of length scaling analysis. Correlation between relief and uplift rate is observed for all length scales of topography shorter than 600 m, which suggests that all orders of the streams are able to adjust to the tectonic signal. Simple mass balance considerations imply that the average elevation is only 10% of surface uplift, suggesting that a dynamic equilibrium has been reached quite rapidly. Using a simple two-process model for erosion, we find that fairly high diffusion coefficients (order of 10 m^2 yr^(\u22121)) and efficient transport of the material by rivers are required. This unusually high value for mass diffusivity at small length scales may be obtained by either a very efficient linear diffusion or by landsliding. Actually, both processes may be active, which appears likely given the nature of the unconsolidated substratum and the favorable climatic conditions. Local relief in the study area may therefore be used to predict either uplift or denudation, but the prediction is calibrated only for that specific climatic and lithologic conditions and cannot be systematically applied to other contexts.", "doi": "10.1029/1998JB900098", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1999-06-10", "series_number": "B6", "volume": "104", "issue": "B6", "pages": "12779-12796" }, { "id": "authors:bfbcx-1pk98", "collection": "authors", "collection_id": "bfbcx-1pk98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120907-155928570", "type": "article", "title": "Radon emanation and electric potential variations associated with transient deformation near reservoir lakes", "author": [ { "family_name": "Trique", "given_name": "M.", "clpid": "Trique-M" }, { "family_name": "Richon", "given_name": "P.", "clpid": "Richon-P" }, { "family_name": "Perrier", "given_name": "F.", "clpid": "Perrier-F" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sabroux", "given_name": "J. C.", "clpid": "Sabroux-J-C" } ], "abstract": "Two of the most often cited earthquake precursors are radon emanation and electric potential variations, but these few reported examples have generally been deemed questionable. If a mechanism relating crustal deformation to radon emanation or electrical signals does indeed exist, it is thought to involve fluids. Some preliminary insight has been gained into these processes from the study of natural systems under controlled mechanical and hydrological conditions. Here we report electric potential variations, radon emanation and deformation measurements recorded since 1995 in the French Alps in the vicinity of two artificial lakes which have strong seasonal variations in water level of more than 50 metres. We observe that electric potential variations and radon emanations are repeatedly associated with transient deformation events induced by variations in lake levels. These events are characterized by a change in ground tilt which deviates from the expected elastic response, and are associated with periods of accelerating strain, which suggests that accelerated loading can enhance fluid transport properties. Qualitatively, this behaviour can be accounted for by a model in which straining induces fluid overpressure and dynamic flow in cracks. These observations may shed light on the sensitivity of rock transport properties to deformation.", "doi": "10.1038/20161", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1999-05-13", "series_number": "6732", "volume": "399", "issue": "6732", "pages": "137-141" }, { "id": "authors:zq6t0-mhg88", "collection": "authors", "collection_id": "zq6t0-mhg88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120906-102733380", "type": "article", "title": "Measuring ground displacements from SAR amplitude images: Application to the Landers Earthquake", "author": [ { "family_name": "Michel", "given_name": "R\u00e9mi", "clpid": "Michel-R" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Taboury", "given_name": "Jean", "clpid": "Taboury-J" } ], "abstract": "ERS SAR amplitude images are utilized to map ground displacements from a sub\u2010pixel correlation method. It yields a ground two\u2010dimensional displacement field with independent measurements about every 128m in azimuth and 250m in range. The accuracy depends on the characteristics of the images. For the Landers test case, the 1\u2010\u03c3 uncertainty is 0.8m in range and 0.4m in azimuth. We show that this measurement provides a map of major surface fault ruptures accurate to better than 1km and information on coseismic deformation comparable to the 92 GPS measurements available. Although less accurate, this technique is more robust than SAR interferometry and provides complementary information since interferograms are only sensitive to the displacement in range.", "doi": "10.1029/1999GL900138", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1999-04-01", "series_number": "7", "volume": "26", "issue": "7", "pages": "875-878" }, { "id": "authors:1hjh9-3fy18", "collection": "authors", "collection_id": "1hjh9-3fy18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120919-115715043", "type": "article", "title": "Anomalous surface waves from Lop Nor nuclear explosions: Observations and numerical modeling", "author": [ { "family_name": "Pedersen", "given_name": "Helle A.", "clpid": "Pedersen-H-A" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Campillo", "given_name": "Michel", "clpid": "Campillo-M" } ], "abstract": "Surface waves from the Chinese test site of Lop Nor are analyzed using long-period and broadband stations located at regional and teleseismic distances and at different azimuths. For most azimuths, strong Love waves between 0.02 and 0.045 Hz are observed with an amplitude of up to 10 times that of the Rayleigh waves. In addition, an anomalous early Rayleigh wave train is observed at some stations in western Europe. Due to a particularly favorable station and source configuration, it is possible to isolate the areas where the anomalies are created. The high-amplitude Love waves must be attributed to either source effects or path effects immediately north of Lop Nor. The early wave train is shown to be due to a partial energy conversion between Love and Rayleigh waves, probably at the Tornquist Zone. To estimate the possible contribution from surface wave conversions to the observed anomalies, numerical simulations are carried out with the indirect boundary element method. The simulations show that a relatively small variation of crustal thickness can induce Rayleigh to Love wave conversions between 0.02 and 0.1 Hz frequency. The calculated amplitudes of the Love waves are significant (up to 35% of the amplitude of the incoming Rayleigh waves), but they are too small to fit the observed amplitude anomaly. The observed converted waves and the numerical results nevertheless indicate that surface wave conversions can be significant across strong lateral crustal heterogeneities. In particular, the conversions due to changes in crustal thickness are located in the period interval which is routinely used for estimation of Ms.", "doi": "10.1029/98JB00027", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1998-07-10", "series_number": "B7", "volume": "103", "issue": "B7", "pages": "15051-15068" }, { "id": "authors:dxhgv-5e072", "collection": "authors", "collection_id": "dxhgv-5e072", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-104206975", "type": "article", "title": "Electric potential variations associated with yearly lake level variations", "author": [ { "family_name": "Perrier", "given_name": "Fr\u00e9d\u00e9ric", "clpid": "Perrier-F" }, { "family_name": "Trique", "given_name": "Micha\u00ebl", "clpid": "Trique-M" }, { "family_name": "Lorne", "given_name": "Benoit", "clpid": "Lorne-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Electric potential variations have been recorded from November 1995 to February 1996 and continuously since October 1996 at 14 measurement points on a one km wide ridge separating two lakes in the French Alps. The levels of the lakes vary by several tens of meters on a yearly cycle, inducing stress variations and fluid percolation. At one point, unambiguous variations as large as 120 mV are observed over a year, linearly correlated with the levels of the lakes with a magnitude of 2 mV per meter of water level change. This particular measurement point lies at the edge of a SP anomaly, which supports the presence of a localized zone of ground water flow forced by the lake level, suggesting an electrokinetic mechanism. The observed correlation implies a \u03b6\u2010potential of the order of \u20108 mV for a 60 \u03a9m electrolyte, in agreement with laboratory measurements.", "doi": "10.1029/98GL01139", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1998-06-01", "series_number": "11", "volume": "25", "issue": "11", "pages": "1955-1958" }, { "id": "authors:r38cr-tha18", "collection": "authors", "collection_id": "r38cr-tha18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120907-131002862", "type": "article", "title": "Slip-partitioning and fore-arc deformation at the Sunda Trench, Indonesia", "author": [ { "family_name": "Baroux", "given_name": "Emmanuel", "clpid": "Baroux-E" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bellier", "given_name": "Olivier", "clpid": "Bellier-O" }, { "family_name": "S\u00e9brier", "given_name": "Michel", "clpid": "S\u00e9brier-M" } ], "abstract": "Oblique subduction at the Sunda Trench has produced transpressive deformation of the plate leading edge. A major feature is the right-lateral Great Sumatran Fault (GSF) which probably absorbs a significant fraction of the trench-parallel shear. The kinematics of Sunda relative to Australia are discussed on the basis of available GPS data, and geologically determined slip rates on the CSF, In spite of the uncertainty on the plate motion, several robust conclusions can be drawn. The predicted obliquity of the convergence increases northward along the Sumatra Trench, up to about 30\u00b0, Slip partitioning is nearly complete along the northern segment of the Sumatra Trench, where the CSF probably accommodates most of the trench parallel shear, Along the southern segment, where obliquity is less than about 20\u00b0, slip-partitioning is not complete as indicated by oblique thrusting at the subduction. There, only a fraction of the trench parallel motion of Australia relative to SE Asia is accommodated along the CSF, These observations suggest that the leading edge behaves like a plastic wedge, except that slip-partitioning, although incomplete, is observed even at low obliquities.", "doi": "10.1046/j.1365-3121.1998.00182.x", "issn": "0954-4879", "publisher": "Blackwell Publishing", "publication": "Terra Nova", "publication_date": "1998-06", "series_number": "3", "volume": "10", "issue": "3", "pages": "139-144" }, { "id": "authors:awhn6-t8969", "collection": "authors", "collection_id": "awhn6-t8969", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-091721561", "type": "article", "title": "Erosion as a driving mechanism of intracontinental\n mountain growth", "author": [ { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Burov", "given_name": "E. B.", "clpid": "Burov-E-B" } ], "abstract": "In nature, mountains can grow and remain as localized tectonic features over long periods of time (> 10 m.y.). By contrast, according to current knowledge of lithospheric rheology and neglecting surface processes, any intracontinental range with a width that exceeds that which can be supported by the strength of the lithosphere should collapse within a few tens of millions of years. For example, assuming a quartz-dominated crustal rheology, the relief of a range initially 3 km high and 300\u2013400 km wide is reduced by half in about 15 m.y. as a result of lateral spreading of its crustal root. We suggest that surface processes might actually prevent such a \"subsurface collapse.\" Removal of material from topographic heights and deposition in the foreland oppose spreading of the crustal root and could eventually drive a net influx of material toward the orogeny. We performed a set of numerical experiments in order to validate this hypothesis. A section of a lithosphere, with a brittle-elasto-ductile rheology, initially loaded by a mountain range is submitted to horizontal shortening and to surface processes. If erosion is intense, material is removed more rapidly than it can be supplied by crustal thickening below the range, and the topography is rapidly smoothed. For example, a feature 3 km high and 300\u2013400 km wide is halved in height in about 15 m.y. for an erosion coefficient k = 10^3 m^2/yr (the erosion rate is of the order of a few 0.1 mm/yr). This regime might be called \"erosional collapse.\" If erosion is not active enough, the crustal root spreads out laterally and \"subsurface collapse\" occurs. In the third intermediate regime, removal of the material by erosion is dynamically compensated by isostatic rebound and inward flow in the lower crust so that the range can grow. In this \"mountain growth\" regime the range evolves toward a characteristic graded shape that primarily depends on the erosion law. The erosion rate may be high (e.g., 0.5\u20130.9 mm/yr), close to the rate of tectonic uplift (e.g., 0.7\u20131.1 mm/yr), and few times higher than the rate of topographic uplift (0.15\u20130.2 mm/yr). These experiments show that surface processes can favor localized crustal shortening and participate in the development of an intracontinental mountain. Surface processes must therefore be taken into account in the interpretation and modeling of long-term deformation of continental lithosphere. Conversely, the mechanical response of the lithosphere must be accounted for when large-scale topographic features are interpreted and modeled in terms of geomorphologic processes.", "doi": "10.1029/96JB01344", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1996-08-10", "series_number": "B8", "volume": "101", "issue": "B8", "pages": "17747-17769" }, { "id": "authors:kyhkm-77j33", "collection": "authors", "collection_id": "kyhkm-77j33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-075845560", "type": "article", "title": "Tectonics of Western Tibet, between the Tarim and the Indus", "author": [ { "family_name": "Matte", "given_name": "Ph.", "clpid": "Matte-Ph" }, { "family_name": "Tapponnier", "given_name": "P.", "clpid": "Tapponnier-P" }, { "family_name": "Arnaud", "given_name": "N.", "orcid": "0000-0001-6589-8673", "clpid": "Arnaud-N" }, { "family_name": "Bourjot", "given_name": "L.", "clpid": "Bourjot-L" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Vidal", "given_name": "Ph.", "clpid": "Vidal-Ph" }, { "family_name": "Qing", "given_name": "Liu", "clpid": "Qing-L" }, { "family_name": "Yusheng", "given_name": "Pan", "clpid": "Yusheng-P" }, { "family_name": "Yi", "given_name": "Wang", "clpid": "Yi-W" } ], "abstract": "A Tarim to Indus traverse provides insight into the tectonics of western Tibet. The Kunlun was the site of a Mid-Paleozoic collision. At least three phases of post-Paleozoic accretion have thickened the blanket of sediments that covers western Tibet. Sizeable parts of western Qiangtang have remained stable, however, since the Mid-Mesozoic. Since the Neogene, deformation and volcanism have been localized near the edges of the Plateau. Strike-slip motion along the Karakorum and Altyn Tagh faults has been coeval with overthrusting in the Himalayas and Kunlun. Such slip partitioning, and the volcanism, appear to result simply from northward subduction of India and southward subduction of the Tarim as Tibet is extruded eastwards by India's penetration into Asia.", "doi": "10.1016/0012-821X(96)00086-6", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1996-08", "series_number": "3-4", "volume": "142", "issue": "3-4", "pages": "311-330" }, { "id": "authors:n7n0h-e1718", "collection": "authors", "collection_id": "n7n0h-e1718", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-113605699", "type": "article", "title": "Seismic anisotropy beneath Tibet: evidence for eastward extrusion of the Tibetan lithosphere?", "author": [ { "family_name": "Lav\u00e9", "given_name": "J.", "clpid": "Lav\u00e9-J" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lacassin", "given_name": "R.", "clpid": "Lacassin-R" }, { "family_name": "Tapponnier", "given_name": "P.", "clpid": "Tapponnier-P" }, { "family_name": "Montagner", "given_name": "J. P.", "orcid": "0000-0001-9958-3012", "clpid": "Montagner-J-P" } ], "abstract": "Strong seismic anisotropy beneath Tibet has recently been reported from the study of SKS shear wave splitting. The fast split waves are generally polarized in an easterly direction, close to the present day direction of motion of the Tibetan crust relative to stable Eurasia, as deduced from Holocene slip rates on the major active faults in and around Tibet. This correlation may be taken to suggest that the whole Tibetan lithosphere is being extruded in front of indenting India and that the anisotropic layer is the deforming asthenosphere, that accommodates the motion of the Tibetan lithosphere relative to the fixed mantle at depth. Uncertainties about this motion are at present too large to bring unambiguous support to that view. Assuming that this view is correct however, a simple forward model is used to compute theoretical delay times as a function of the thickness of the anisotropic layer. The observed delay times would require a 50\u2013100 km thick anisotropic layer beneath south-central Tibet and an over 200 km thick layer beneath north-central Tibet, where particularly hot asthenosphere has been inferred. This study suggests that the asthenospheric anisotropy due to present absolute block motion might be dominant under actively deforming continents.", "doi": "10.1016/0012-821X(96)00045-3", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1996-05", "series_number": "1-4", "volume": "140", "issue": "1-4", "pages": "83-96" }, { "id": "authors:nf0mf-t6f64", "collection": "authors", "collection_id": "nf0mf-t6f64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-090527005", "type": "article", "title": "Palaeoclimatic interpretation of a topographic profile across middle Holocene regressive shorelines of Longmu Co (Western Tibet)", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Dobremez", "given_name": "Jean-Fran\u00e7ois", "clpid": "Dobremez-J-F" }, { "family_name": "Bourjot", "given_name": "Laurence", "clpid": "Bourjot-L" } ], "abstract": "Most lakes and closed basins in Tibet are surrounded by abandoned shorelines attesting for high-water levels in the past. Two such lakes, Longmu Co and Sumxi Co (Western Tibet), were the focus of detailed palaeoclimatic work during the 1989 Sino-French expedition based on the study of lake sediments and analysis of a piston core. Here it is shown that additional information may be deduced from the abandoned shorelines around Longmu Co. A 1800 m long topographic profile was levelled from 75 m up to 230 m above the present lake elevation (5008 m), on which the shorelines form a flight of horizontal terraces separated by more or less degraded scarps. The elevations of the terraces were spaced regularly about 1.35 m, except for 3\u20135 m high lacunae reccurring every 15\u201316 m. The potential annual evapo-transpiration was computed based on meteorological data collected at Tien Shui Hai from 13/08/89 to 11/09/90. Using a modified Penman formula a value of 1.60 \u00b1 0.3 m/yr was obtained under close system conditions (no outlet) and a synthetic curve of lake regression was derived which appears to be consistent with the measured shoreline heights. It is concluded that the 1.35 m terraces represent annual regression of the lake level. By contrast, the 3\u20135 m high lacunae might reflect the periodic return, about every 9\u201312 yr, of particular climatic conditions responsible for a perturbation of the annual process of shoreline formation. All the shorelines of this profile have formed probably within one century, during a continuous and abrupt regression of the lake. Such evolution has also been identified in the sediments of a piston core collected at Sumxi Co, and dated at about 6-5.5 kyr B.P. The lake level must have been at its highest stand, shortly before that major regression. The mechanism responsible for this middle Holocene high stand and for the major sudden drop of the lake level remains uncertain.", "doi": "10.1016/0031-0182(96)88700-1", "issn": "0031-0182", "publisher": "Elsevier", "publication": "Palaeogeography, Palaeoclimatology, Palaeoecology", "publication_date": "1996-02", "series_number": "1-2", "volume": "120", "issue": "1-2", "pages": "93-104" }, { "id": "authors:k7ch9-q6x66", "collection": "authors", "collection_id": "k7ch9-q6x66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-135400575", "type": "article", "title": "Interseismic Strain Accumulation on the Himalayan Crustal\n Ramp (Nepal)", "author": [ { "family_name": "Pandey", "given_name": "M. R.", "clpid": "Pandey-M-R" }, { "family_name": "Tandukar", "given_name": "R. P.", "clpid": "Tandukar-R-P" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lav\u00e9", "given_name": "J.", "clpid": "Lav\u00e9-J" }, { "family_name": "Massot", "given_name": "J. P.", "clpid": "Massot-J-P" } ], "abstract": "The Departement of Mines and Geology has been monitoring the seismicity of the Central Himalayas of Nepal since 1985. Intense microseismicity and frequent medium\u2010size earthquakes (mL<4) tend to cluster beneath the topographic front of the Higher Himalaya. This 10\u201320km deep seismicity also correlates with a zone of localized uplift that has been evidenced from geodetic data. Both microseismic and geodetic data indicate strain accumulation on a mid\u2010crustal ramp that had been previously inferred from geological and geophysical evidence. This ramp connects a flat decollement under the Lesser and Sub\u2010Himalaya with a deeper decollement under the Higher Himalaya, and probably acts as a geometric asperity where strain and stress build up during the interseismic period. The large Himalayan earthquakes could nucleate there and probably activate the whole flat\u2010and\u2010ramp system up to the blind thrusts of the Sub\u2010Himalaya.", "doi": "10.1029/94GL02971", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1995-04-01", "series_number": "7", "volume": "22", "issue": "7", "pages": "751-754" }, { "id": "authors:5mrjg-h4v16", "collection": "authors", "collection_id": "5mrjg-h4v16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-093114587", "type": "article", "title": "Preliminary Early Cretaceous paleomagnetic results from the Gansu Corridor, China", "author": [ { "family_name": "Frost", "given_name": "Gina Marie", "clpid": "Frost-G-M" }, { "family_name": "Coe", "given_name": "Richard S.", "orcid": "0000-0003-3225-4235", "clpid": "Coe-R-S" }, { "family_name": "Meng", "given_name": "Zifang", "clpid": "Meng-Zifang" }, { "family_name": "Peng", "given_name": "Zuolin", "clpid": "Peng-Zuolin" }, { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Courtillot", "given_name": "Vincent", "clpid": "Courtillot-V" }, { "family_name": "Peltzer", "given_name": "Gilles", "clpid": "Peltzer-G" }, { "family_name": "Tapponnier", "given_name": "Paul", "clpid": "Tapponnier-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "We report results from our paleomagnetic study of Lower Cretaceous redbeds from the Gansu Corridor, northwestern China. The characteristic remanent magnetization (ChRM) resides in hematite, often at very high unblocking temperatures (> 660\u00b0C). The directions associated with this component exhibit only reversed polarities from locality A (Sunan area), but the samples from locality B (Lanzhou area, 480 km to the southeast) show roughly antipodal normal and reversed polarities. The combined sample directional data from both localities pass a fold test at the 99% confidence level. The mean paleomagnetic pole is located at 48.7\u00b0N, 199.7\u00b0E, with A_(95) = 4.1\u00b0, which is discordant with poles of similar age elsewhere from neighboring regions in China. Although represented by relatively few samples (N = 21) this pole suggests that significant post-Cretaceous motion may have occurred between the Gansu Corridor and adjacent blocks. Relative to Eurasia or North China, the discordance corresponds to 28.1 \u00b1 5.2\u00b0 or 35.6\u00b0 \u00b1 9.7\u00b0 clockwise rotation and 9.5\u00b0 \u00b1 4.5\u00b0 or 9.8\u00b0 \u00b1 8.2\u00b0 northward displacement respectively. The rotations support, but do not yet distinguish between, several neotectonic models assumed to have acted over the past 15\u201340 m.y. The displacement is not predicted by any of these models; if real, it may have occurred early in the history of the India-Asia collision, or even before.", "doi": "10.1016/0012-821X(94)00244-S", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1995-01", "series_number": "1-4", "volume": "129", "issue": "1-4", "pages": "217-232" }, { "id": "authors:r3ak2-x6m32", "collection": "authors", "collection_id": "r3ak2-x6m32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-130301707", "type": "article", "title": "Kinematics of the Asal Rift (Djibouti) Determined from the Deformation of Fieale Volcano", "author": [ { "family_name": "de Chabalier", "given_name": "Jean-Bernard", "clpid": "de-Chabalier-J-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Because of its subaerial exposure the Asal rift segment provides an exceptional opportunity to quantify the deformation field of an active rift and assess the contribution of tectonics and volcanism to rifting processes. The present topography of the Asal rift results from the tectonic dismemberment during the last 100,000 years of a large central volcanic edifice that formed astride the rift zone 300,000 to 100,000 years ago. Three-dimensional deformation of this volcano has been quantified from the combined analysis of the topography and geology. The analysis indicates that spreading at 17 to 29 millimeters per year in a N40\u00b0 \u00b1 5\u00b0E direction accounts for most of the separation between Arabia and Somalia. The small topographic subsidence relative to extension suggests that tectonic thinning of the crust has been balanced by injection and underplating of magmatic material of near crustal density. The methodology developed in this study could also be applied to quantify deformation in relatively inaccessible areas where the main available information is topography or bathymetry.", "doi": "10.1126/science.265.5179.1677", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1994-09-16", "series_number": "5179", "volume": "265", "issue": "5179", "pages": "1677-1681" }, { "id": "authors:hznr8-e2591", "collection": "authors", "collection_id": "hznr8-e2591", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-113704833", "type": "article", "title": "Crustal and upper-mantle structure under the Tien Shan\n from surface-wave dispersion", "author": [ { "family_name": "Cotton", "given_name": "F.", "clpid": "Cotton-F" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Long-period seismograms of nuclear explosions and natural earthquakes in central Asia, recorded at three digital stations of the Laboratoire de D\u00e9tection G\u00e9ophysique (LDG) network in France, attest to a significant propagation effect in the Tien Shan area. This allows for an investigation of the deep structures under the range, which has been the site of particularly intense intracontinental deformation since about the middle Miocene. Group velocity curves have been obtained by regionalization for pure paths across either the central or eastern Tien Shan. They indicate a crust of approximately 50\u201355 km in thickness, and particularly low shear-wave velocities under the central Tien Shan. Our study suggests lateral variation of the deep structures under the range, which could be related to a westward increase along the range of cumulative amount and rate of shortening.", "doi": "10.1016/0031-9201(94)90036-1", "issn": "0031-9201", "publisher": "Elsevier", "publication": "Physics of the Earth and Planetary Interiors", "publication_date": "1994-07", "series_number": "1-4", "volume": "84", "issue": "1-4", "pages": "95-109" }, { "id": "authors:zmbsn-zdh69", "collection": "authors", "collection_id": "zmbsn-zdh69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-103543102", "type": "article", "title": "Active Tectonics in Southern Xinjiang, China: Analysis of Terrace Riser and Normal Fault Scarp Degradation Along the Hotan-Qira Fault System", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Peltzer", "given_name": "Gilles", "clpid": "Peltzer-G" } ], "abstract": "The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal fault system vertically offsets the piedmont slope by 70 m. Highest fault scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwalls have formed inset terraces. We have leveled topographic profiles across fault scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient \u03c4, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 \u00b1 4 m^2. Profiles of cumulative fault scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental fault scarp model. The analysis shows that (1) rate of fault slip remained essentially constant since the aggradation of the piedmont surface and (2) the occurrence of inset terraces was synchronous at all studied sites, suggesting a climate-driven terrace formation. Observation of glacial and periglacial geomorphic features along the northern front of the western Kunlun range indicates that the Qira glaciofluvial fan emplaced after the last glacial maximum, during the retreat of the Kunlun glaciers (12\u201322 ka). The age of the most developed inset terrace in uplifted valleys is inferred to be 10 \u00b1 3 ka, coeval with humid climate pulses of the last deglaciation. The mass diffusivity constant (k=\u03c4/T, being time B.P.) in the Hotan region is determined to be 3.3 \u00b1 1.4 m^2/10^3 years, consistent with other estimates in similar climatic and geologic environments of western China. These results imply a minimum rate for the Tarim subsidence of 3.5 \u00b1 2 mm/yr. If Western Kunlun overthrusts the Tarim platform on a crustal ramp dipping 40\u00b0\u201345\u00b0 to the south, it would absorb at least 4.5 \u00b1 3 mm/yr of convergence between western Tibet and Tarim.", "doi": "10.1029/93JB02172", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1993-12-10", "series_number": "B12", "volume": "98", "issue": "B12", "pages": "21773-21807" }, { "id": "authors:nm74m-nfa33", "collection": "authors", "collection_id": "nm74m-nfa33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-151739673", "type": "article", "title": "Late Quaternary kinematics of the Pallatanga strike-slip fault (Central Ecuador) from topographic measurements of displaced morphological features", "author": [ { "family_name": "Winter", "given_name": "Thierry", "clpid": "Winter-T" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Lavenu", "given_name": "Alain", "clpid": "Lavenu-A" } ], "abstract": "The northeast-trending Pallatanga right-lateral strike-slip fault runs across the Western Cordillera connecting N50\u00b0E-N70\u00b0E trending normal faults in the Gulf of Guayaquil with N-S reverse faults in the Interandean Depression. Over most of its length, the fault trace has been partly obscured by erosional processes and can be inferred in the topography only at the large scale. Only the northern fault segment, which follows the upper Rio Pangor valley at elevations above 3600 m, is prominent in the morphology. Valleys and ridges cut and offset by the fault provide an outstanding record of right-lateral cumulative fault displacement. The fault geometry and kinematics of this particular fault segment can be determined from detailed topographic levellings. The fault strikes N30\u00b0E and dips 75\u00b0 to the NW. Depending on their size and nature, transverse morphological features such as tributaries of the Rio Pangor and intervening ridges, reveal right-lateral offsets which cluster around 27 \u00b1 11m, 41.5 \u00b1 4 m, 590 \u00b1 65 m and 960 \u00b1 70 m. The slip vector deduced from the short-term offsets shows a slight reverse component with a pitch of about 11.5\u00b0 SW. The 41.5 \u00b1 4 m displacements are assumed to be coeval with the last glacial termination, yielding a mean Holocene slip-rate of 2.9- 4.6 mm yr^(\u22121). Assuming a uniform slip rate on the fault in the long term, the 27 m offset appears to correlate with an identified middle Holocene morphoclimatic event, and the long term offsets of 590 m and 960 m coincide with the glacial terminations at the beginning of the last two interglacial periods.", "doi": "10.1111/j.1365-246X.1993.tb01500.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "1993-12", "series_number": "3", "volume": "115", "issue": "3", "pages": "905-920" }, { "id": "authors:tq7ka-ntf57", "collection": "authors", "collection_id": "tq7ka-ntf57", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-105620191", "type": "article", "title": "Kinematic model of active deformation in central Asia", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Tapponnier", "given_name": "Paul", "clpid": "Tapponnier-P" } ], "abstract": "The velocity field of present\u2010day deformation in Central Asia is modelled using a set of four rotating blocks (Siberia, Tarim, Tibet, India) on a spherical earth. A best\u2010fit is inverted on the basis of estimated shortening\u2010rates across the main thrust zones (Himalayas, Tien Shan) and measured slip\u2010rates along the principal strike\u2010slip faults (Altyn Tagh and Karakorum) separating those blocks. The fit to the data implies that nearly all the present convergence between India and Asia can be accounted for by slip\u2010partitioning on these four zones, with as much as 50% absorbed by northeastwards extrusion of Tibet. This suggests that localised deformation governs the present mechanical behaviour of the Central Asian lithosphere.", "doi": "10.1029/93GL00128", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1993-05-21", "series_number": "10", "volume": "20", "issue": "10", "pages": "895-898" }, { "id": "authors:xae58-vp504", "collection": "authors", "collection_id": "xae58-vp504", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-102136624", "type": "article", "title": "Analysis of Scarp Profiles: Evaluation of Errors in Morphologic Dating", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Morphologic analysis of scarp degradation can be used quantitatively to determine relative ages of different scarps formed in cohesionless materials, under the same climatic conditions. Scarps of tectonic origin as well as wavecut or rivercut terraces can be treated as topographic impulses that are attenuated by surface erosional processes. This morphological evolution can be modelled as the convolution of the initial shape with erosion (or degradation) function whose width increases with time. Such modeling applies well to scarps less than 10m high, formed in unconsolidated fanglomerates. To a good approximation, the degradation function is Gaussian with a variance measuring the degree of rounding of the initial shape. This geometric parameter can be called the degradation coefficient. A synthetic experiment shows that the degradation coefficient can be obtained by least squares fitting of profiles levelled perpendicular to the scarp. Gravitational collapse of the free face is accounted for by assuming initial scarp slopes at the angle of repose of the cohesionless materials (30\u00b0\u201335\u00b0). Uncertainties in the measured profiles result in an uncertainty in degradation coefficient that can be evaluated graphically. Because the degradation coefficient is sensitive to the regional slope and to three-dimensional processes (gullying, loess accumulation, stream incision, etc.), a reliable and accurate determination of degradation coefficient requires several long profiles across the same scarp. The linear diffusion model of scarp degradation is a Gaussian model in which the degradation coefficient is proportional to numerical age. In that case, absolute dating requires only determination of the propotionality constant, called the mass diffusivity constant. For Holocene scarps a few meters high, in loose alluvium under arid climatic conditions, mass diffusivity constants generally range between 1 and 6 m^2/kyr. Morphologic analysis is a reliable method to compare ages of different scarps in a given area, and it can provide approximate absolute ages of Holocene scarplike landforms.", "doi": "10.1029/92JB01962", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1993-04-10", "series_number": "B4", "volume": "98", "issue": "B4", "pages": "6745-6754" }, { "id": "authors:teg2e-5mp15", "collection": "authors", "collection_id": "teg2e-5mp15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-113758232", "type": "article", "title": "Active Thrusting and Folding Along the Northern Tien Shan and Late Cenozoic Rotation of the Tarim Relative to Dzungaria and Kazakhstan", "author": [ { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Tapponnier", "given_name": "P.", "clpid": "Tapponnier-P" }, { "family_name": "Bai", "given_name": "M.", "clpid": "Bai-M" }, { "family_name": "You", "given_name": "H.", "clpid": "You-H" }, { "family_name": "Wang", "given_name": "G.", "clpid": "Wang-G" } ], "abstract": "We have studied geometries and rates of late Cenozoic thrust faulting and folding along the northern piedmont of the Tien Shan mountain belt, West of Urumqi, where the M= 8.3 Manas earthquake occurred on December 23, 1906. The northern range of the Tien Shan, rising above 5000 m, overthrusts a flexural foredeep, filled with up to 11,000 m of sediment, of the Dzungarian basement. Our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front, within a 200-km-long zone of Neogene-Quaternary anticlines. Fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range. In all the valleys, the scarps offset vertically the highest terrace surface by the same amount (10.2\u00b10.7 m). Inferring an early Holocene age (10\u00b12 kyr) for this terrace, which is continuous with the largest recent fans of the piedmont, yields a rate of vertical throw of 1.0\u00b10.3mm/yr on the main active thrust at the surface. A quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5.5\u00b12.5 m^2/kyr. A rather fresh surface scarp, 0.8\u00b10.15 m high, that is unlikely to result from shallow earthquakes with 6 < M < 7 in the last 230 years, is visible at the extremities of the main fold zone. We associate this scarp with the 1906 Manas earthquake and infer that a structure comprising a deep basement ramp under the range, gently dipping flats in the foreland, and shallow ramps responsible for the formation of the active, fault propagation anticlines could have been activated by that earthquake. If so, the return period of a 1906 type event would be 850 \u00b1380 years. The small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth (\u22482/3) is taken up by incremental folding near the surface. Comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising Quaternary ranges such as the San Gabriel mountains in California or the Mont Blanc-Aar massifs in the Alps. We estimate the finite Cenozoic shortening of the folded Dzungarian sediments to be of the order of 30 km and the Cenozoic shortening rate to have been 3 \u00b1 1.5 mm/yr. Assuming comparable shortening along the Tarim piedmont and minor additional active thrusting within the mountain belt, we infer the rate of shortening across the Tien Shan to be at least 6 \u00b1 3 mm/yr at the longitude of Manas (\u224885.5\u00b0E). A total shortening of 125\u00b130 km is estimated from crustal thickening, assuming local Airy isostatic equilibrium. Under the same assumption, serial N-S sections imply that Cenozoic shortening across the belt increases westwards to 203\u00b150 km at the longitude of Kashgar (\u2248 76 \u00b0E), as reflected by the westward increase of the width of the belt. This strain gradient implies a clockwise rotation of Tarim relative to Dzungaria and Kazakhstan of 7\u00b12.5\u00b0 around a pole located near the eastern extremity of the Tien Shan, west of Hami (\u224896\u00b0E, 43.5\u00b0N), comparable to that revealed by paleomagnetism between Tarim and Dzungaria (8.6\u00b0 \u00b1 8.7\u00b0). A 6 mm/yr rate of shortening at the longitude of Manas would imply a rate of rotation of 0.45\u00b0/m.y. and would be consistent with a shortening rate of 12 mm/yr north of Kashgar. Taking such values to be representative of Late Cenozoic rates would place the onset of reactivation of the Tien Shan by the India-Asia collision in the early to middle Miocene (16 +22/\u22129 m.y.), in accord with the existence of particularly thick late Neogene and Quaternary deposits. Such reactivation would thus have started much later than the collision, roughly at the time of the great mid-Miocene changes in tectonic regimes, denudation and sedimentation rates observed in southeast Asia, the Himalayas and the Bay of Bengal, and of the correlative rapid change in seawater Sr isotopic ratio (20 to 15 Ma). Like these other changes, the rise of the Tien Shan might be a distant consequence of the end of Indochina's escape.", "doi": "10.1029/92JB01963", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1993-04-10", "series_number": "B4", "volume": "98", "issue": "B4", "pages": "6755-6804" }, { "id": "authors:x1vwv-x0w06", "collection": "authors", "collection_id": "x1vwv-x0w06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-155007302", "type": "article", "title": "Kinematic model of active deformation in Central Asia", "author": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Tapponnier", "given_name": "Paul", "clpid": "Tapponnier-P" } ], "abstract": "The velocity field of present deformation in Central Asia is modelled with four rotating\nblocks (Siberia, Tarim, Tibet, India) on a spherical earth. A best-fitting model is inverted from\nestimated shortening- and slip-rates on the main thrust (Himalayas, Tien Shan) and strike-slip zones\n(Altyn Tagh, Karakorum) between those blocks. The good fit to the data implies that most of the\npresent convergence between India and Asia is absorbed by motion on these four zones. Localised\ndeformation thus governs the mechanical behaviour of the Central Asian lithosphere.", "issn": "0764-4450", "publisher": "Gauthier-Villars", "publication": "Comptes rendus de l'Acad\u00e9mie des sciences S\u00e9rie II", "publication_date": "1992-12-17", "series_number": "13", "volume": "315", "issue": "13", "pages": "1791-1798" }, { "id": "authors:thhbc-kat74", "collection": "authors", "collection_id": "thhbc-kat74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120910-114313483", "type": "article", "title": "On the growth of normal faults and the existence of flats and ramps along the El Asnam active fold and thrust system", "author": [ { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Meyer", "given_name": "B.", "clpid": "Meyer-B" }, { "family_name": "Tapponnier", "given_name": "P.", "clpid": "Tapponnier-P" } ], "abstract": "The combination of detailed topographic leveling on the southwest segment of the El Asnam thrust fault with existing seismic and geologic data implies that the geometry of this fault involves shallow dipping flats and steep ramps. The fault appears to be growing along strike toward the southwest end, where the main shock initiated in 1980. From a depth of about 10 km, the main thrust appears to ramp to the basement-Cenozoic cover interface on a plane striking N40\u00b0E and dipping 50\u00b0\u201355\u00b0 to the northwest. Along the southwest segment where folding has not yet developed, the thrust continues steeply through the Cenozoic cover to the near surface where it flattens, causing normal faulting. Along the central and northeast segments, which display a more evolved fold structure, the deep thrust probably flattens at a depth of 5\u20136 km, into a decollement along the Cenozoic-Jurassic interface before ramping to the surface. The Sara El Marouf and Kef El Mes anticlines have thus formed as fault propagation folds. Normal faults at Beni Rached probably branch with the thrust to maintain kinematic compatibility between the deep ramp and decollement. The greater separation (\u223c7 km) between the normal faults at Beni Rached and the thrust where it crosses Oued Cheliff than along the southwest segment (\u223c1 km) reflects the greater depth of the ramp to flat bend. We infer that the September 9, 1954, earthquake activated only the central deep segment of the main thrust together with the Beni Rached normal faults, while that of October 10, 1980, activated the whole system of flat decollements, ramp thrusts and compatibility normal faults. Further complexities of the faulting in map view are related to changes of strike of the thrust (in particular north of Oued Cheliff).", "doi": "10.1029/91TC01449", "issn": "0278-7407", "publisher": "American Geophysical Union", "publication": "Tectonics", "publication_date": "1992-02", "series_number": "1", "volume": "11", "issue": "1", "pages": "1-11" }, { "id": "authors:cz0km-9tn63", "collection": "authors", "collection_id": "cz0km-9tn63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120911-152435568", "type": "article", "title": "Paleomagnetic Study of Mesozoic Continental Sediments Along the Northern Tien Shan (China) and Heterogeneous Strain in Central Asia", "author": [ { "family_name": "Chen", "given_name": "Yan", "clpid": "Chen-Yan" }, { "family_name": "Cogne", "given_name": "Jean-Pascal", "clpid": "Cogne-J-P" }, { "family_name": "Courtillot", "given_name": "Vincent", "clpid": "Courtillot-V" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Tapponnier", "given_name": "Paul", "clpid": "Tapponnier-P" }, { "family_name": "Wang", "given_name": "Gongque", "clpid": "Wang-Gongque" }, { "family_name": "Bai", "given_name": "Meixiang", "clpid": "Bai-M" }, { "family_name": "You", "given_name": "Hongzi", "clpid": "You-Hongzi" }, { "family_name": "Li", "given_name": "Ming", "clpid": "Li-Ming" }, { "family_name": "Wei", "given_name": "Chunsheng", "clpid": "Wei-Chunsheng" }, { "family_name": "Buffetaut", "given_name": "Eric", "clpid": "Buffetaut-E" } ], "abstract": "A paleomagnetic study of rocks from the northern foot of the Tien Shan and the southern border of the Dzungar Basin, east of Urumqi (44.2\u00b0N, 86.0\u00b0E), spanning ages from middle Jurassic to early Tertiary was carried out to constrain the tectonic evolution in central Asia since Mesozoic time. Five middle Jurassic sites reveal a remagnetized direction close to the present Earth field in geographic coordinates: D = 6.6\u00b0, I = 72.6\u00b0 (\u03b1_(95) = 7.4\u00b0). Thirteen out of 17 upper Jurassic and lower Cretaceous sites yield a characteristic direction (stratigraphic coordinates) of D = 12.7\u00b0, I = 48.6\u00b0 (\u03b1_(95) = 5.5\u00b0). Nine of 16 upper Cretaceous and lower Tertiary sites provide a characteristic direction of D = 12.5\u00b0, I = 51.3\u00b0 (\u03b1_(95) = 6.9\u00b0). The latter two directions pass fold and reversal tests. The pole positions are close to each other and to the Besse and Courtillot [1989, 1990] Eurasian apparent polar wander path, for ages ranging from 130 to 70 Ma. However, the difference in paleolatitudes amounts to about 5.9\u00b0 \u00b1 3.7\u00b0, which could indicate significant continental shortening in the Altai Mountains and perhaps further north, subsequent to India-Asia collision. The pole positions from the Dzungar Basin are close to those found for the Tarim [Li et al., 1988a], leading to an insignificant paleolatitude difference (3.0\u00b0 \u00b1 6.9\u00b0), but showing a larger difference in declination (8.6\u00b0 \u00b1 8.7\u00b0). These paleomagnetic results are compatible with a model of heterogeneous deformation in the western part of the collision zone between India and Siberia. A significant shortening in the Altai, a slight counterclockwise rotation of the Dzungar block, the westward-increasing shortening in the Tien Shan with attendant clockwise rotation of the Tarim block are all consistent with this model, in which Tibet, the Tien Shan and the Altai undergo differential strain along strike in a relay fashion, with the total India-Siberia convergence remaining approximately constant.", "doi": "10.1029/90JB02699", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1991-03-10", "series_number": "B3", "volume": "96", "issue": "B3", "pages": "4065-4082" }, { "id": "authors:ccqht-vfs85", "collection": "authors", "collection_id": "ccqht-vfs85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120920-082609701", "type": "article", "title": "Mesures topographiques sur le segment SW de Ia zone faill\u00e9e d'El Asnam et interpr\u00e9tation m\u00e9canique des relations entre failles inverses et normales", "author": [ { "family_name": "Meyer", "given_name": "Bertrand", "clpid": "Meyer-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Tapponnier", "given_name": "Paul", "clpid": "Tapponnier-P" }, { "family_name": "Meghraoui", "given_name": "Mustapha", "clpid": "Meghraoui-M" } ], "abstract": "Using topographic measurements, we document the relationship between thrust movement along the SW segment of the El Asnam fault, and normal movements on secondary faults in the hanging wall. Cumulative displacements of calcarenite beds on the normal faults of this\nsegment correspond to an increasing number of seismic events towards the north. This suggests a southwards propagation of the faulted structure. In\nthe zone between the SW and central segments of the El Asnam fault, near Zebabdja, one sees the passage from the reverse fault, activated in 1980\nto a normal fault. This observation, and the monoclinal lithology, suggest that normal faults merge with the main reverse faults plane where bedding\nforces this plane to dip more gently. These normal faults, which strike perpendicular to the regional compressive stress, maintain the kinematic compatibility\nbetween over and underthrusted blocks. These observations allow us to propose a kinematic model for the SW segment of El Asnam fault zone.", "issn": "0037-9409", "publisher": "Soci\u00e9t\u00e9 G\u00e9ologique de France", "publication": "Bulletin de la Soci\u00e9t\u00e9 G\u00e9ologique de France", "publication_date": "1990-05", "series_number": "3", "volume": "8", "issue": "3", "pages": "447-456" }, { "id": "authors:mxre0-kxf20", "collection": "authors", "collection_id": "mxre0-kxf20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120919-154348340", "type": "article", "title": "Active thrusting and folding in the Qilian Shan, and decoupling between upper crust and mantle in northeastern Tibet", "author": [ { "family_name": "Tapponnier", "given_name": "P.", "clpid": "Tapponnier-P" }, { "family_name": "Meyer", "given_name": "B.", "clpid": "Meyer-B" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Peltzer", "given_name": "G.", "clpid": "Peltzer-G" }, { "family_name": "Gaudemer", "given_name": "Y.", "clpid": "Gaudemer-Y" }, { "family_name": "Shunmin", "given_name": "Guo", "clpid": "Shunmin-G" }, { "family_name": "Hongfa", "given_name": "Xiang", "clpid": "Hongfa-X" }, { "family_name": "Kelun", "given_name": "Yin", "clpid": "Kelun-Y" }, { "family_name": "Zhitai", "given_name": "Chen", "clpid": "Zhitai-C" }, { "family_name": "Shuahua", "given_name": "Cai", "clpid": "Shuahua-C" }, { "family_name": "Huagang", "given_name": "Dai", "clpid": "Huagan-D" } ], "abstract": "Fieldwork south of the city of Gaotai (Gansu province, China) shows that active shortening of surface sediments in the foothills of the Yumu Shan, a large fore-mountain of the Qilian Shan, at the northeastern edge of Tibet, involves both overthrusting and flexural-slip folding. North of this mountain, we found and mapped a prominent north-facing thrust scarp that offsets a Holocene fan sloping gently (3.4\u00b0) to the north. Part of this scarp appears to be related to the M \u2248 7.5, 180 A.D. earthquake that may have led to the demise of the Han Dynasty city of Luo Tuo Chen, in the Hexi corridor. A set of 10, 100\u2013150 m long profiles measured across this scarp, 3.2 m high on the average, can be made to fit the diffusion-degraded morphology of a surface break related to the 180 A.D. event using a value of about 3.3 m^2/10^3 yr for the mass diffusivity \u03f0 of fanglomerates in this part of Gansu province. Smaller mountain-facing scarps on a terrace-capped foothill result from bedding slip concurrent with active folding of underlying, steeply northdipping, Plioquaternary sandstone and conglomerate beds. Holocene uplift rates along the Yumu Shan, which is only one of the Qilian Shan ranges, are estimated to be between 0.4 and 1.9 mm/yr, which implies that much of the mountain formed in the Quaternary. The periclinal structure of the Plioquaternary envelope under which the Paleozoic core of the Yumu Shan plunges towards the west suggests that the whole 3200 m high mountain is a basement ramp anticline. Mountains striking parallel to the Yumu Shan, with similar structure and comparable or greater sizes north and south of the Hexi corridor probably also correspond to recent, crustal ramp anticlines. This implies that the wide, mountainous upper crustal wedge making the northeastern edge of the Tibet-Qinghai plateau is detached from the underlying lower crust and upper mantle.", "doi": "10.1016/0012-821X(90)90053-Z", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1990-03", "series_number": "3-4", "volume": "97", "issue": "3-4", "pages": "382-403" } ]