This thesis comprises three distinct studies, each drawing on multiple, diverse datasets and modeling approaches to investigate the thermo-mechanical behavior of Earth's crust and mantle in different tectonic regimes.
\r\n\r\nThe first study addresses the longstanding debate regarding the stratified rheological structure of the Tibetan lithosphere using constraints from postseismic deformation and climate-driven hydrological loading at a range of timescales. By leveraging multiple geodetic datasets and geological records of time-dependent surface deformation, with a focus on the postseismic deformation following the 2021 Mw 7.4 Maduo earthquake, this study proposes a regional model that can explain observations across spatial and temporal scales more consistently. Our results reveal a low-viscosity zone in the middle crust of Tibet (20\u201340 km depth), consistent with many previous studies. However, the viscosity we infer for this layer is sufficiently high to imply strong mechanical coupling between the upper and lower crust (or the under-thrusting Indian lithosphere).
\r\n\r\nThe second study assesses the role of hydrous material in seismic detectability of slabs in Earth's lower mantle from a mineral physics perspective. It highlights the need to consider both temperature and composition when interpreting seismic observations for identifying structures, such as paleoslabs. Recent experiments show that hydrous phases (e.g., δ-Fe13 and (Al,Fe)-phase H) can coexist with basaltic assemblages under lower mantle conditions, and can thus alter the aggregate properties of slab material. Using mineral physics modeling, which incorporates new experimental data for these hydrous phases, this study examines the thermo-elastic and geophysical properties of lower mantle petrologies, including hydrous slabs, in the context of recent observations of seismic scatterers and reflectors, geodynamical constraints, and global tomography. Most prominently, it shows that hydrous phases can render cold subducted slabs seismically \u201cinvisible\u201d, challenging the common assumption that slabs are distinctly faster than the ambient mantle at all mantle depths.
\r\n\r\nThe third study investigates the vertical motions of the Pacific seafloor in the Cretaceous using a newly developed Bayesian inversion method (InvoPlates) that constrains mantle thermal anomalies using lithosphere subsidence records over millions of years, present-day bathymetry, and paleo-carbonate compensation depths (CCD). The west-central Pacific\u2019s anomalously shallow bathymetry (\u201cPacific Superswell\u201d) and anomalous subsidence of atolls and guyots have been attributed to the \"Darwin Rise\", postulated to be a large superswell in the Cretaceous. This study constrains the spatio-temporal aspects of the Darwin Rise, which shows close correlation with the Ontong-Java Plateau formation, while de-tangling intrinsic plate cooling from lithosphere re-heating. It also challenges the traditional paleo-CCD reconstructions which link temporal CCD changes solely to changing ocean chemistry, key in models of long-term global carbon cycle, without considering time-varying plate-age independent vertical motions of the seafloor.
", "doi": "10.7907/gc13-j049", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:16630", "collection": "thesis", "collection_id": "16630", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08132024-035518437", "primary_object_url": { "basename": "MyCaltechThesis_TaehoKim.pdf", "content": "final", "filesize": 102966987, "license": "other", "mime_type": "application/pdf", "url": "/16630/2/MyCaltechThesis_TaehoKim.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Modeling Frictional Processes in the Presence of Fluids: From Earthquakes in the Laboratory to Induced Seismicity in Geothermal Reservoirs", "author": [ { "family_name": "Kim", "given_name": "Taeho", "orcid": "0000-0002-2560-7728", "clpid": "Kim-Taeho" } ], "thesis_advisor": [ { "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" } ], "thesis_committee": [ { "family_name": "Fu", "given_name": "Xiaojing", "orcid": "0000-0001-7120-704X", "clpid": "Fu-Xiaojing" }, { "family_name": "Bhattacharya", "given_name": "Kaushik", "orcid": "0000-0003-2908-5469", "clpid": "Bhattacharya-K" }, { "family_name": "Faulkner", "given_name": "Daniel R.", "orcid": "0000-0002-6750-3775", "clpid": "Faulkner-Daniel-R" }, { "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" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Induced seismicity - earthquakes driven by injections of fluids into the subsurface - is of growing societal importance in its impact on clean energy technology. Advancements central to the world\u2019s transition to a greener economy such as geothermal energy and long-term geologic storage of CO2 are hampered by a lack of understanding and control of the associated seismic hazards. In its mechanics, frictional processes in the presence of fluids is a difficult problem to model given the challenges of studying frictionally unstable material in a controlled environment. Unstable gouge material is commonly found along faults in nature, due to pulverization of brittle rock in to granular layers called `gouge.' This thesis approaches the challenge at two different scales: 1. at the scale of the localized shear layer along the interface between two faults where we model laboratory earthquakes in the presence of pressurized fluids, and 2. at the scale of a reservoir where we model the rate of earthquakes given the injection/extraction schedule.
\r\n\r\nIn order to infer the frictional properties of unstable gouge material from laboratory experiments, we develop a probabilistic model based on a spring-slider representation of the experiment along with the rate-and-state friction law. Inversions indicate that the presence of pressurized pore fluids stabilizes the gouge - by an increase in the strength of the contacts and a lesser decrease in the grain size with slip - even under the same effective normal stress. Assuming purely slip-dependent healing of friction leads to an evolution of parameters with slip that is consistent with previously established interpretations of rate-and-state parameters. The best fitting spring-slider model still shows significant discrepancies to the experiment in the evolution of creep and in the dependence on loading rate. A quasi-static finite-element model with the same rate-and-state properties suggests that the gouge in the sample likely slides in a spatially uniform manner. Thus, the discrepancies between the spring-slider model and the experiment can likely be attributed to flaws in the rate-and-state formalism and the slip law rather than the idealization of a finite geometry to a single-degree-of-freedom system. The results prove that quantitative analysis of frictional processes of gouge in the unstable regime is possible, and that future development of constitutive relationships for friction should aim to reproduce key features of stick-slip in detail.
\r\n\r\nTo model seismicity induced by a geothermal well stimulation, we develop physical and statistical models of the seismicity rate. The physical models are based on rate-and-state friction and stress changes due to pore-pressure diffusion. The statistical model performs a convolution of a kernel function inspired by Omori law decay with the injection rate. Both models successfully reproduce the seismicity observed during the 2018 enhanced geothermal system (EGS) simulation in Otaniemi, Finland. We find that the effect of time-dependent nucleation from rate-and-state friction is crucial in reproducing the temporal and spatial patterns of the observed seismicity. We also find that the effect of finite nucleation cannot be approximated well by introducing a stress threshold in the standard Coulomb friction model, at least in the context of rapid variations of injection rates common in EGS operations.
\r\n\r\nWe highlight the major assumptions of the Dieterich seismicity rate model and examine how they may bias interpretations of induced seismicity observed in real reservoirs by comparing it directly to a Discrete Fault Network (DFN) model. The spatio-temporal pattern of seismicity in the finite setting is not only dependent on fluid transport properties and its combination with nucleation characteristics but also the distribution of initial conditions of the fault network. The back-propagation front, in particular, occurs co-injection if the time to instability for the minimum slip rate is shorter than the injection duration. The relocated catalogue of the 1993 GPK1 stimulation in Soultz-Sous-Forets shows such a back-front which can be fit qualitatively using the time to instability measure. A simple model for the rate of magnitudes that accounts for the evolution of frictional stability reproduces the apparent increase in the source radius of induced events in Soultz-Sous-Forets. The rate of larger events is overestimated by the model, possibly due to an overestimation of maximum magnitudes by the volume of stimulation. The comparisons reveal that parameters of the Dieterich model lack clear physical meaning in the finite analogue and highlight the importance of using realistic physics, especially in models at large scales where uncertainty due to assumptions at smaller scales may be amplified.
\r\n \r\nWe end the thesis with the application of rate-and-state friction to dynamic rupture modeling of seismic data from distributed acoustic sensing (DAS). The modeling of the high-frequency DAS recordings of a Magnitude 6.0 earthquake suggests a highly heterogeneous underlying fault with several prominent asperities and barriers that may control rupture dynamics. The model demonstrates how the high-stress patches both inhibit and promote the overall rupture, while also contributing to a significant amount of the energy release themselves. The successful interpretations of modern seismological data encourage future development efficient models that can be used for dynamic inversions.
", "doi": "10.7907/pp3a-2609", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16392", "collection": "thesis", "collection_id": "16392", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05202024-162817936", "primary_object_url": { "basename": "Sirorattanakul_PhDThesis_2024.pdf", "content": "final", "filesize": 188097142, "license": "other", "mime_type": "application/pdf", "url": "/16392/1/Sirorattanakul_PhDThesis_2024.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Response of Earthquakes to Transient Stresses, in Laboratory and Nature", "author": [ { "family_name": "Sirorattanakul", "given_name": "Krittanon", "orcid": "0000-0003-2310-8447", "clpid": "Sirorattanakul-Krittanon" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Rosakis", "given_name": "Ares J.", "clpid": "Rosakis-A-J" } ], "thesis_committee": [ { "family_name": "Zhan", "given_name": "Zhongwen", "orcid": "0000-0002-5586-2607", "clpid": "Zhan-Zhongwen" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "local_group": [ { "literal": "Center for Geomechanics and Mitigation of Geohazards (GMG)" }, { "literal": "div_gps" } ], "abstract": "Earthquake rates are known to fluctuate with time according to the changing state of stress in the Earth\u2019s crust. Studying the response of earthquakes to transient stresses provides a unique insight into the mechanisms controlling the earthquake nucleation process. Common sources of transient stresses include stress changes from fault slip during large earthquakes, spontaneous slow fault slip, fluid pressure diffusion, seasonal changes of water mass and snowpacks related to hydrological cycles, tidal stresses from changes of gravitational forces of the Sun and the Moon, and anthropogenic fluid injection and extraction related to geoenergy production. In this\r\nthesis, we first start in the laboratory-scale fault and conduct friction experiments to enhance our understanding of the underlying friction laws used for modeling earthquakes. We find that the traditional view of Coulomb friction, which postulates that there exists a threshold shear force called \u201cstatic friction,\u201d below which the frictional interface remains stationary, is incorrect. Our measurements have shown that such an interface is still sliding, albeit with extremely small decaying slip rates down to 10^{\u221212} m/s. This is consistent with a more recently developed friction law, which describes friction as dependent on slip rate and the state of the interface, e.g., time since the last earthquake. Next, we move beyond the laboratory and study natural faults. In one example, we study the response of earthquakes to transient stress induced by a spontaneous slow fault slip event that preceded the earthquake swarm\r\nsequence by approximately half a day. In another example, we study the response of earthquakes to seasonal stress perturbations as a result of seasonal changes in groundwater mass and snowpack between wet and dry seasons, using California as a case study. In both examples, we find that earthquake nucleation is not an instantaneous process. Rather the earthquake rates lag after the stress rates. Such behavior cannot be described by Coulomb friction but can be quantitatively explained by the rate- and state-dependent friction. In the final example, we document bursts of fast propagating swarms of induced earthquakes at the Groningen gas field in the Netherlands. While transient stress must exist to drive the sequence, we cannot explicitly quantify the sources. Overall, our work provides key insights into the earthquake nucleation process, allowing us to better understand how to model the response of earthquakes to transient stress, including earthquakes that are induced by anthropogenic activities related to geoenergy production.", "doi": "10.7907/2fgg-0m89", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:14651", "collection": "thesis", "collection_id": "14651", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302022-071239478", "primary_object_url": { "basename": "PhD_thesis_Stacy_Larochelle.pdf", "content": "final", "filesize": 94832965, "license": "other", "mime_type": "application/pdf", "url": "/14651/1/PhD_thesis_Stacy_Larochelle.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Mechanical Interactions Between Water and the Solid Earth: from Quasi-Static Geodetic Deformation to Dynamic Fault Slip", "author": [ { "family_name": "Larochelle", "given_name": "Stacy", "orcid": "0000-0001-6161-5605", "clpid": "Larochelle-Stacy" } ], "thesis_advisor": [ { "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" } ], "thesis_committee": [ { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "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" } ], "local_group": [ { "literal": "Center for Geomechanics and Mitigation of Geohazards (GMG)" }, { "literal": "div_gps" } ], "abstract": "Mechanical interactions between Earth's solid interior and its hydrosphere are central to many geophysical problems of crucial societal importance: Changing conditions in the global water cycle deform the solid Earth; the groundwater storage capacity of aquifer systems is controlled by its interaction with geological materials; and crustal water - either natural occurring or added through anthropogenic activities - affects earthquakes and fault slip processes. In this thesis, we investigate some of these interactions by harnessing recent developments in the fields of satellite geodesy, statistical data analysis and elastodynamic earthquake modelling. We start by developing a procedure to identify and extract seasonal deformation signals associated with hydrological loading of the solid Earth from geodetic time series in Chapter 1. In Chapters 2 and 3, we consider the examples of the Ozarks Plateau (central United States) and Sacramento Valley (California) to establish a methodology for characterizing poroelastic deformation arising from groundwater variations with space-based geodesy. Then, in Chapter 4, we develop a model to simulate fault slip due to crustal water injections and calibrate it against a well-instrumented field experiment on a natural fault. We conclude by deriving a theoretical understanding of these fault slip simulations by considering the simple case of a fixed-length pressurized zone in Chapter 5. Overall, our work provides key insights for extracting and using different sources of hydrogeodetic signals as well as for modeling and understanding fluid-induced fault slip processes, which is becoming increasingly important in a world faced with water scarcity, a changing climate and an increased reliance on groundwater and geoenergy resources.
", "doi": "10.7907/2r5a-9277", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14167", "collection": "thesis", "collection_id": "14167", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05202021-183729767", "primary_object_url": { "basename": "RobackThesis-final.pdf", "content": "final", "filesize": 6346301, "license": "other", "mime_type": "application/pdf", "url": "/14167/2/RobackThesis-final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Investigating Sand Transport and Landslides, and Implications for Past and Present Environments on Mars and Earth", "author": [ { "family_name": "Roback", "given_name": "Kevin Patrick", "orcid": "0000-0001-5209-2873", "clpid": "Roback-Kevin-Patrick" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Wind-driven movement of sand and landslide activity are among the most important processes driving modern-day change on planetary surfaces. This thesis uses novel techniques and datasets to investigate the forces driving these processes on the surface of Mars, and also considers possible applications of the techniques described to Earth. Chapter 1 introduces past work done to understand these processes, and outstanding questions our work aims to answer. Chapter 2 presents and tests a new technique which aims to improve predictions of sand transport driven by wind on planetary surfaces by correcting coarse-resolution GCM predictions for the short-timescale fluctuations they miss. Chapter 3 presents new multiyear measurements of ripple migration at two dune fields on the surface of Mars, and applies these measurements, in conjunction with the new techniques described in Chapter 2, to investigate the dynamics of the Martian atmosphere, and test the accuracy of predictions made by Martian climate models. In Chapter 4, we study a large-scale natural sand trap in the Meroe Patera dune field on Mars, and estimate its trapped volume of sand in comparison to the volume of \"missing\" sand in a dune-free shadow zone downwind of the crater. The volume of trapped sand is far less than the missing volume, suggesting past escape of sand from the crater, despite a lack of obvious evidence for such escape in the present day. In Chapter 5, we change focus from sand transport to introduce an analysis of controls on the global distribution of Martian landslides. Chapter 6 discusses the limitations of applying the techniques of satellite image and climate model analysis described in Chapters 2-4 to terrestrial settings, as well as the possible utility of Chapter 5\u2019s method on other planets.
", "doi": "10.7907/gykg-wz60", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:10563", "collection": "thesis", "collection_id": "10563", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11202017-145930076", "type": "thesis", "title": "Using Heterogeneous 3D Earth Models to Constrain Interseismic and Postseismic Deformation in Southern California and Nepal", "author": [ { "family_name": "Rollins", "given_name": "John Christopher", "orcid": "0000-0002-5291-6956", "clpid": "Rollins-John-Christopher" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" } ], "thesis_committee": [ { "family_name": "Gurnis", "given_name": "Michael C.", "clpid": "Gurnis-M-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Lapusta", "given_name": "Nadia", "clpid": "Lapusta-N" }, { "family_name": "Clayton", "given_name": "Robert W.", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "We characterize interseismic strain accumulation across the Los Angeles basin and postseismic deformation following the 2010 Mw=7.2 El Mayor-Cucapah and 2015 Mw=7.8 Nepal earthquakes using geodetic data. These settings are all characterized by strong 3D heterogeneities of elastic structure, ductile properties, fault geometries, and fault slip behavior, and we use constaints from seismology, long-term tectonic modeling, geology, and other sources to construct detailed models of these heterogeneities. Postseismic surface displacements following the 2010 El Mayor-Cucapah earthquake indicate viscoelastic relaxation in the shallow Salton Trough mantle and possibly the lower crust, a process that would have been enhanced by high heat flow induced by crustal extension at the tip of the Gulf of California. We find that a dense and prolonged aftershock sequence in the Yuha Desert may have been driven by aseismic afterslip coupled with fluid flow. Our study of interseismic strain accumulation across the Los Angeles basin shows that the soft sedimentary basin has a first-order effect on the elastostatic Green\u2019s functions mapping fault creep and locking at depth to surface deformation, and therefore on the estimation of interseismic fault creep rates and strain accumulation at depth. We infer modest interseismic coupling on the three major thrust faults underlying the Los Angeles basin, corresponding to an annual seismic moment deficit buildup rate (to be presumably released in earthquakes) of 1.7 +1.2/-0.5 x 1017 Nm/yr. We estimate the long-term seismicity model needed to balance the rate of moment deficit accumulation assuming a truncated Gutenberg-Richter magnitude-frequency distribution of earthquakes. The long-term catalog is consistent with the instrumental rates of small and moderate earthquakes and tops out at a M~6.9 earthquake every ~430 years. Finally, we characterize the postseismic deformation following the 2015 Nepal earthquake using models of the thermal structure, state of stress, and rheology that are based on the long-term evolution and topography of the Himalaya. The rheological structure based on these models predicts negligible postseismic viscoelastic deformation. Afterslip on the downdip extension of the rupture cannot realistically explain the observed displacements either. We find that the postseismic deformation is well explained by a combination of afterslip on the downdip edge of the coseismic rupture (as well as a narrow zone in between the mainshock and a large aftershock) and, more prominently, transient viscoelastic relaxation in the hot Tibetan crust. These processes contribute to the stress loading of the Main Himalayan Thrust.
", "doi": "10.7907/Z9X06572", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10134", "collection": "thesis", "collection_id": "10134", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04072017-164424209", "primary_object_url": { "basename": "Malatesta_Luca_2017.pdf", "content": "final", "filesize": 44055235, "license": "other", "mime_type": "application/pdf", "url": "/10134/1/Malatesta_Luca_2017.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Impact of Climate and Tectonics on the Morphodynamics of Alluvial Piedmonts, Implications for Sediment Transfer and the Stratigraphic Record\r ", "author": [ { "family_name": "Malatesta", "given_name": "Luca Claude", "orcid": "0000-0003-0983-715X", "clpid": "Malatesta-Luca-Claude" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Lamb", "given_name": "Michael P.", "clpid": "Lamb-M-P" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Adkins", "given_name": "Jess F.", "clpid": "Adkins-J-F" }, { "family_name": "Fischer", "given_name": "Woodward W.", "clpid": "Fischer-W-W" }, { "family_name": "Grotzinger", "given_name": "John P.", "clpid": "Grotzinger-J-P" }, { "family_name": "Lamb", "given_name": "Michael P.", "clpid": "Lamb-M-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Alluvial piedmonts encircle most of the Earth mountain ranges. The erosion product of these mountains must cross the piedmont domain before reaching the basins where they can enter the sedimentary record. The flux of sediment transfers environmental signals, e.g. tectonics and climate, from source to sink, their preservation is critical for the sedimentary record. Alluvial piedmonts are very reactive to external and internal forcing often incise by tens to hundreds of vertical meters over a few thousand years only to subsequently aggrade by roughly the same amount. In my thesis, I set to study the morphodynamics of alluvial piedmonts in two areas, Death Valley, California, and the Eastern Tian Shan.
\r\n\r\nIn Death Valley I show that cycles of aggradation and incision repeatedly bury active fault scarps and that leads to the accumulation of tectonic slip until the next incision episode when a tall waterfall is released in the catchment. This process links the release of tectonic offset to climatic periods and it also accounts for many unexplained 10 to 30 m waterfalls in the Death Valley area. In the Eastern Tian Shan, I establish that the northern alluvial piedmont, that is incised by 100 to 300 m in the Holocene, undergoes repeated cycles of aggradation and incision driven by fluctuations in Westerlies moisture and insolation at a 21 kyr period without the need for monsoonal moisture to drive the system. The varying extent of glacial overprint in the Eastern Tian Shan is responsible for the morphological contrast between the incised north and aggraded south piedmonts. I produce more terrace abandonment ages that show that all rivers of the northern piedmont incised since the last deglaciation but did so out of sync because of the geometry of the upstream glaciated valleys, and internal feedbacks with alluvial valley walls during river entrenchment. With new luminescence ages sampled in the stratigraphy I establish that sediments from the last 0.5 Myr are remobilized in the modern sediment flux by the alluvial incision. I develop a numerical tool that predicts locally the probability of sediment mixing based on the essential length- and timescales of the individual rivers of an alluvial piedmont.
", "doi": "10.7907/Z9HD7SP4", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9767", "collection": "thesis", "collection_id": "9767", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-131105966", "primary_object_url": { "basename": "Stevens_Victoria_20162.pdf", "content": "final", "filesize": 12986561, "license": "other", "mime_type": "application/pdf", "url": "/9767/1/Stevens_Victoria_20162.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Reconciling Geodetic Strain and Seismicity Rate with Frequency-Magnitude Relation of the Largest Earthquakes", "author": [ { "family_name": "Stevens", "given_name": "Victoria Louise", "orcid": "0000-0003-3174-9949", "clpid": "Stevens-Victoria-Louise" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Tsai", "given_name": "Victor C.", "clpid": "Tsai-V-C" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The aim of this thesis is to study how moment buildup rate on faults can be reconciled with moment release rate. We concentrate first on the Himalaya region and go on to look at faults worldwide. We first justify the extrapolation of GPS data in the Himalayan region over the approximate timescale of an earthquake cycle. To do this we show that GPS strain rates correlate with seismicity rates, and that the principal directions of strain found from GPS data are similar to those from earthquake moment tensors, showing that GPS data has been consistent at the timescale of earthquake strain-rate build-up, roughly 100-1000 years.
\r\n\r\nWe next use geodetic data to show that the Main Himalayan Thrust (MHT) is locked from the surface to roughly 100 km north along its entire length, with no creeping patches. We also find the long-term slip rate on the fault, and these values agree with values from geomorphic studies, showing that here the tectonic regime has been stable with time, and most of the deformation is elastic. However, we also find a correspondence between the pattern of uplift rate predicted from the model and the topography, suggesting that a small amount of permanent deformation (10%) may occur, and again suggesting that the pattern of coupling has been stable with time.
\r\n\r\nWe find the moment build-up rate on the MHT to be 15.1\u00b11.0x1019 Nm/yr and compare this rate with the rate of moment release estimated from large earthquakes that have occurred on this fault in the past 1000 years. We use the conservation of moment principal to model the most likely maximum magnitude earthquake that needs to occur to balance the moment budget, and find that we need an earthquake of magnitude 9 or more with a recurrence time of roughly 800 years.
\r\n\r\nWe extend this analysis to faults with no GPS data, and no long record of large earthquakes, by developing a method to find the expected maximum magnitude earthquake on faults assuming conservation of moment, and that the earthquakes follow the Gutenberg-Richter law. Our results compare well with historical catalogs where they are available.
", "doi": "10.7907/Z9PN93K7", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:7953", "collection": "thesis", "collection_id": "7953", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09112013-133205322", "primary_object_url": { "basename": "PhD_thesis_thomas_marion_fontcor.pdf", "content": "final", "filesize": 260903591, "license": "other", "mime_type": "application/pdf", "url": "/7953/49/PhD_thesis_thomas_marion_fontcor.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Frictional Properties of Fault: From Observations on the Longitudinal Valley Fault, Taiwan, to Dynamic Simulations", "author": [ { "family_name": "Thomas", "given_name": "Marion Y.", "clpid": "Thomas-Marion-Y" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Lapusta", "given_name": "Nadia", "clpid": "Lapusta-N" } ], "thesis_committee": [ { "family_name": "Asimow", "given_name": "Paul David", "clpid": "Asimow-P-D" }, { "family_name": "Wernicke", "given_name": "Brian P.", "clpid": "Wernicke-B-P" }, { "family_name": "Lapusta", "given_name": "Nadia", "clpid": "Lapusta-N" }, { "family_name": "Heaton", "given_name": "Thomas H.", "clpid": "Heaton-T-H" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Faults can slip either aseismically or through episodic seismic ruptures, but we still do not understand the factors which determine the partitioning between these two modes of slip. This challenge can now be addressed thanks to the dense set of geodetic and seismological networks that have been deployed in various areas with active tectonics. The data from such networks, as well as modern remote sensing techniques, indeed allow documenting of the spatial and temporal variability of slip mode and give some insight. This is the approach taken in this study, which is focused on the Longitudinal Valley Fault (LVF) in Eastern Taiwan. This fault is particularly appropriate since the very fast slip rate (about 5 cm/yr) is accommodated by both seismic and aseismic slip. Deformation of anthropogenic features shows that aseismic creep accounts for a significant fraction of fault slip near the surface, but this fault also released energy seismically, since it has produced five M_w>6.8 earthquakes in 1951 and 2003. Moreover, owing to the thrust component of slip, the fault zone is exhumed which allows investigation of deformation mechanisms. In order to put constraint on the factors that control the mode of slip, we apply a multidisciplinary approach that combines modeling of geodetic observations, structural analysis and numerical simulation of the \"seismic cycle\". Analyzing a dense set of geodetic and seismological data across the Longitudinal Valley, including campaign-mode GPS, continuous GPS (cGPS), leveling, accelerometric, and InSAR data, we document the partitioning between seismic and aseismic slip on the fault. For the time period 1992 to 2011, we found that about 80-90% of slip on the LVF in the 0-26 km seismogenic depth range is actually aseismic. The clay-rich Lichi M\\'elange is identified as the key factor promoting creep at shallow depth. Microstructural investigations show that deformation within the fault zone must have resulted from a combination of frictional sliding at grain boundaries, cataclasis and pressure solution creep. Numerical modeling of earthquake sequences have been performed to investigate the possibility of reproducing the results from the kinematic inversion of geodetic and seismological data on the LVF. We first investigate the different modeling strategy that was developed to explore the role and relative importance of different factors on the manner in which slip accumulates on faults. We compare the results of quasi dynamic simulations and fully dynamic ones, and we conclude that ignoring the transient wave-mediated stress transfers would be inappropriate. We therefore carry on fully dynamic simulations and succeed in qualitatively reproducing the wide range of observations for the southern segment of the LVF. We conclude that the spatio-temporal evolution of fault slip on the Longitudinal Valley Fault over 1997-2011 is consistent to first order with prediction from a simple model in which a velocity-weakening patch is embedded in a velocity-strengthening area.", "doi": "10.7907/0AFX-WS57", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7861", "collection": "thesis", "collection_id": "7861", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072013-041618148", "primary_object_url": { "basename": "BellePhilibosian_Dissertation2013_final.pdf", "content": "final", "filesize": 12935596, "license": "other", "mime_type": "application/pdf", "url": "/7861/1/BellePhilibosian_Dissertation2013_final.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Characterization of Diverse Megathrust Fault Behavior Related to Seismic Supercycles, Mentawai Islands, Sumatra", "author": [ { "family_name": "Philibosian", "given_name": "Belle", "clpid": "Philibosian-Belle" } ], "thesis_advisor": [ { "family_name": "Sieh", "given_name": "Kerry E.", "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" } ], "thesis_committee": [ { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Sieh", "given_name": "Kerry E.", "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": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Long paleoseismic histories are necessary for understanding the full range of behavior of faults, as the most destructive events often have recurrence intervals longer than local recorded history. The Sunda megathrust, the interface along which the Australian plate subducts beneath Southeast Asia, provides an ideal natural laboratory for determining a detailed paleoseismic history over many seismic cycles. The outer-arc islands above the seismogenic portion of the megathrust cyclically rise and subside in response to processes on the underlying megathrust, providing uncommonly good illumination of megathrust behavior. Furthermore, the growth histories of coral microatolls, which record tectonic uplift and subsidence via relative sea level, can be used to investigate the detailed coseismic and interseismic deformation patterns. One particularly interesting area is the Mentawai segment of the megathrust, which has been shown to characteristically fail in a series of ruptures over decades, rather than a single end-to-end rupture. This behavior has been termed a seismic \u201csupercycle.\u201d Prior to the current rupture sequence, which began in 2007, the segment previously ruptured during the 14th century, the late 16th to late 17th century, and most recently during historical earthquakes in 1797 and 1833. In this study, we examine each of these previous supercycles in turn.
\r\n\r\nFirst, we expand upon previous analysis of the 1797\u20131833 rupture sequence with a comprehensive review of previously published coral microatoll data and the addition of a significant amount of new data. We present detailed maps of coseismic uplift during the two great earthquakes and of interseismic deformation during the periods 1755\u20131833 and 1950\u20131997 and models of the corresponding slip and coupling on the underlying megathrust. We derive magnitudes of Mw 8.7\u20139.0 for the two historical earthquakes, and determine that the 1797 earthquake fundamentally changed the state of coupling on the fault for decades afterward. We conclude that while major earthquakes generally do not involve rupture of the entire Mentawai segment, they undoubtedly influence the progression of subsequent ruptures, even beyond their own rupture area. This concept is of vital importance for monitoring and forecasting the progression of the modern rupture sequence.
\r\n\r\nTurning our attention to the 14th century, we present evidence of a shallow slip event in approximately A.D. 1314, which preceded the \u201cconventional\u201d megathrust rupture sequence. We calculate a suite of slip models, slightly deeper and/or larger than the 2010 Pagai Islands earthquake, that are consistent with the large amount of subsidence recorded at our study site. Sea-level records from older coral microatolls suggest that these events occur at least once every millennium, but likely far less frequently than their great downdip neighbors. The revelation that shallow slip events are important contributors to the seismic cycle of the Mentawai segment further complicates our understanding of this subduction megathrust and our assessment of the region\u2019s exposure to seismic and tsunami hazards.
\r\n\r\nFinally, we present an outline of the complex intervening rupture sequence that took place in the 16th and 17th centuries, which involved at least five distinct uplift events. We conclude that each of the supercycles had unique features, and all of the types of fault behavior we observe are consistent with highly heterogeneous frictional properties of the megathrust beneath the south-central Mentawai Islands. We conclude that the heterogeneous distribution of asperities produces terminations and overlap zones between fault ruptures, resulting in the seismic \u201csupercycle\u201d phenomenon.
\r\n", "doi": "10.7907/E0QH-YT77", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7828", "collection": "thesis", "collection_id": "7828", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032013-180145987", "primary_object_url": { "basename": "PhD_thesis_Ader.pdf", "content": "final", "filesize": 103680719, "license": "other", "mime_type": "application/pdf", "url": "/7828/1/PhD_thesis_Ader.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Earthquakes of the Nepal Himalaya : Towards a Physical Model of the Seismic Cycle", "author": [ { "family_name": "Ader", "given_name": "Thomas Joachim", "clpid": "Ader-Thomas-Joachim" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" } ], "thesis_committee": [ { "family_name": "Simons", "given_name": "Mark", "clpid": "Simons-M" }, { "family_name": "Lapusta", "given_name": "Nadia", "clpid": "Lapusta-N" }, { "family_name": "Ampuero", "given_name": "Jean-Paul", "clpid": "Ampuero-J-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Home to hundreds of millions of souls and land of excessiveness, the Himalaya is also the locus of a unique seismicity whose scope and peculiarities still remain to this day somewhat mysterious. Having claimed the lives of kings, or turned ancient timeworn cities into heaps of rubbles and ruins, earthquakes eerily inhabit Nepalese folk tales with the fatalistic message that nothing lasts forever. From a scientific point of view as much as from a human perspective, solving the mysteries of Himalayan seismicity thus represents a challenge of prime importance. Documenting geodetic strain across the Nepal Himalaya with various GPS and leveling data, we show that unlike other subduction zones that exhibit a heterogeneous and patchy coupling pattern along strike, the last hundred kilometers of the Main Himalayan Thrust fault, or MHT, appear to be uniformly locked, devoid of any of the \u201ccreeping barriers\u201d that traditionally ward off the propagation of large events. The approximately 20 mm/yr of reckoned convergence across the Himalaya matching previously established estimates of the secular deformation at the front of the arc, the slip accumulated at depth has to somehow elastically propagate all the way to the surface at some point. And yet, neither large events from the past nor currently recorded microseismicity nearly compensate for the massive moment deficit that quietly builds up under the giant mountains. Along with this large unbalanced moment deficit, the uncommonly homogeneous coupling pattern on the MHT raises the question of whether or not the locked portion of the MHT can rupture all at once in a giant earthquake. Univocally answering this question appears contingent on the still elusive estimate of the magnitude of the largest possible earthquake in the Himalaya, and requires tight constraints on local fault properties. What makes the Himalaya enigmatic also makes it the potential source of an incredible wealth of information, and we exploit some of the oddities of Himalayan seismicity in an effort to improve the understanding of earthquake physics and cipher out the properties of the MHT. Thanks to the Himalaya, the Indo-Gangetic plain is deluged each year under a tremendous amount of water during the annual summer monsoon that collects and bears down on the Indian plate enough to pull it away from the Eurasian plate slightly, temporarily relieving a small portion of the stress mounting on the MHT. As the rainwater evaporates in the dry winter season, the plate rebounds and tension is increased back on the fault. Interestingly, the mild waggle of stress induced by the monsoon rains is about the same size as that from solid-Earth tides which gently tug at the planets solid layers, but whereas changes in earthquake frequency correspond with the annually occurring monsoon, there is no such correlation with Earth tides, which oscillate back-and-forth twice a day. We therefore investigate the general response of the creeping and seismogenic parts of MHT to periodic stresses in order to link these observations to physical parameters. First, the response of the creeping part of the MHT is analyzed with a simple spring-and-slider system bearing rate-strengthening rheology, and we show that at the transition with the locked zone, where the friction becomes near velocity neutral, the response of the slip rate may be amplified at some periods, which values are analytically related to the physical parameters of the problem. Such predictions therefore hold the potential of constraining fault properties on the MHT, but still await observational counterparts to be applied, as nothing indicates that the variations of seismicity rate on the locked part of the MHT are the direct expressions of variations of the slip rate on its creeping part, and no variations of the slip rate have been singled out from the GPS measurements to this day. When shifting to the locked seismogenic part of the MHT, spring-and-slider models with rate-weakening rheology are insufficient to explain the contrasted responses of the seismicity to the periodic loads that tides and monsoon both place on the MHT. Instead, we resort to numerical simulations using the Boundary Integral CYCLes of Earthquakes algorithm and examine the response of a 2D finite fault embedded with a rate-weakening patch to harmonic stress perturbations of various periods. We show that such simulations are able to reproduce results consistent with a gradual amplification of sensitivity as the perturbing period get larger, up to a critical period corresponding to the characteristic time of evolution of the seismicity in response to a step-like perturbation of stress. This increase of sensitivity was not reproduced by simple 1D-spring-slider systems, probably because of the complexity of the nucleation process, reproduced only by 2D-fault models. When the nucleation zone is close to its critical unstable size, its growth becomes highly sensitive to any external perturbations and the timings of produced events may therefore find themselves highly affected. A fully analytical framework has yet to be developed and further work is needed to fully describe the behavior of the fault in terms of physical parameters, which will likely provide the keys to deduce constitutive properties of the MHT from seismological observations.", "doi": "10.7907/z9c8276q", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7836", "collection": "thesis", "collection_id": "7836", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042013-203949761", "primary_object_url": { "basename": "Lin-Yunung-Nina-2013.pdf", "content": "final", "filesize": 34547031, "license": "other", "mime_type": "application/pdf", "url": "/7836/1/Lin-Yunung-Nina-2013.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Using Space Geodesy to Constrain Variations in Seismogenic Behavior on Subduction Megathrusts", "author": [ { "family_name": "Lin", "given_name": "Yunung Nina", "clpid": "Lin-Yunung-Nina" } ], "thesis_advisor": [ { "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" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "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": "Ampuero", "given_name": "Jean-Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The concept of seismogenic asperities and aseismic barriers has become a useful paradigm within which to understand the seismogenic behavior of major faults. Since asperities and barriers can be thought of as defining the potential rupture area of large megathrust earthquakes, it is thus important to identify their respective spatial extents, constrain their temporal longevity, and to develop a physical understanding for their behavior. Space geodesy is making critical contributions to the identification of slip asperities and barriers but progress in many geographical regions depends on improving the accuracy and precision of the basic measurements. This thesis begins with technical developments aimed at improving satellite radar interferometric measurements of ground deformation whereby we introduce an empirical correction algorithm for unwanted effects due to interferometric path delays that are due to spatially and temporally variable radar wave propagation speeds in the atmosphere. In chapter 2, I combine geodetic datasets with complementary spatio-temporal resolutions to improve our understanding of the spatial distribution of crustal deformation sources and their associated temporal evolution \u2013 here we use observations from Long Valley Caldera (California) as our test bed. In the third chapter I apply the tools developed in the first two chapters to analyze postseismic deformation associated with the 2010 Mw=8.8 Maule (Chile) earthquake. The result delimits patches where afterslip occurs, explores their relationship to coseismic rupture, quantifies frictional properties associated with inferred patches of afterslip, and discusses the relationship of asperities and barriers to long-term topography. The final chapter investigates interseismic deformation of the eastern Makran subduction zone by using satellite radar interferometry only, and demonstrates that with state-of-art techniques it is possible to quantify tectonic signals with small amplitude and long wavelength. Portions of the eastern Makran for which we estimate low fault coupling correspond to areas where bathymetric features on the downgoing plate are presently subducting, whereas the region of the 1945 M=8.1 earthquake appears to be more highly coupled.", "doi": "10.7907/0V1J-T074", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7853", "collection": "thesis", "collection_id": "7853", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06062013-135816595", "primary_object_url": { "basename": "YWang_Theis_2013.pdf", "content": "final", "filesize": 36806514, "license": "other", "mime_type": "application/pdf", "url": "/7853/54/YWang_Theis_2013.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Earthquake Geology of Myanmar", "author": [ { "family_name": "Wang", "given_name": "Yu", "clpid": "Wang-Yu" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "thesis_committee": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "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" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis describes the active structures of Myanmar and its surrounding regions, and the earthquake geology of the major active structures. Such investigation is needed urgently for this rapidly developing country that has suffered from destructive earthquakes in its long history. To archive a better understanding of the regional active tectonics and the seismic potential in the future, we utilized a global digital elevation model and optical satellite imagery to describe geomorphologic evidence for the principal neotectonic features of the western half of the Southeast Asia mainland. Our investigation shows three distinct active structural systems that accommodate the oblique convergence between the Indian plate and Southeast Asia and the extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Each of these active deformation belts can be further separated into several neotectonic domains, in which structures show distinctive active behaviors from one to another.
\r\n\r\nIn order to better understand the behaviors of active structures, we focused on the active characteristics of the right-lateral Sagaing fault and the oblique subducting northern Sunda megathrust in the second part of this thesis. The detailed geomorphic investigations along these two major plate-interface faults revealed the recent slip behavior of these structures, and plausible recurrence intervals of major seismic events. We also documented the ground deformation of the 2011 Tarlay earthquake in remote eastern Myanmar from remote sensing datasets and post-earthquake field investigations. The field observation and the remote sensing measurements of surface ruptures of the Tarlay earthquake are the first study of this kind in the Myanmar region.
\r\n", "doi": "10.7907/XWW2-9P26", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:6844", "collection": "thesis", "collection_id": "6844", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03052012-150035418", "type": "thesis", "title": "Microstructural, Metamorphic and Experimental Constraints on Differential Stress and Temperature in the Middle Crust", "author": [ { "family_name": "Kidder", "given_name": "Steven Brooks", "clpid": "Kidder-Steven-Brooks" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Because shear stress drives plate tectonics and causes earthquakes, important objectives in the Earth Sciences include quantifying stress magnitudes and variability in space and time, and developing and improving tools to do so. This thesis addresses both objectives. In the first chapter I demonstrate that the Titanium-in-quartz thermobarometer (\"TitaniQ\") can be used to accurately record deformation temperatures under greenschist facies conditions. In the second chapter, an experimental study, I show that the relationship between recrystallized grain size and flow stress (the \u201crecrystallized grain size paleopiezometer\u201d) can be used to determine the stress history of dynamically recrystallized quartz under non steady state conditions. In the third chapter I apply the paleopiezometer in Taiwan\u2019s Hs\u00fcehshan range and compare results to independent constraints (e.g. critical taper theory and potential energy considerations). This analysis demonstrates: 1) the piezometer is accurate to within a factor of two or better under conditions at the brittle-ductile transition; 2) piezometric results are consistent with recent flow laws for quartz; 3) the activation energy of naturally deformed quartzite is >133 kJ/mol, consistent with experimental determinations; and 4) Peak differential stress in the Hs\u00fcehshan range was ~210 MPa at temperature ~300\u00b0C. Our results indicate hydrostatic fluid pressure and a low friction coefficient of ~0.38 within the Taiwan wedge. Integrated crustal strength in Taiwan is 1.5-2.1*1012 N/m, consistent with the force needed to support the topography of the range. The final chapter investigates stress levels on the Vincent thrust in the San Gabriel Mountains, California by constructing a numerical model of the initiation of flat slab subduction. A model inversion demonstrates that previously hypothesized high stresses are not required to explain inverted metamorphism along the fault.", "doi": "10.7907/R9RS-1A13", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:2257", "collection": "thesis", "collection_id": "2257", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05292008-113958", "primary_object_url": { "basename": "Ozgun_Konca_thesis_2008.pdf", "content": "final", "filesize": 8030764, "license": "other", "mime_type": "application/pdf", "url": "/2257/1/Ozgun_Konca_thesis_2008.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Investigating Large Earthquake Rupture Kinematics from the Joint Analysis of Seismological, Geodetic and Remote Sensing Data", "author": [ { "family_name": "Konca", "given_name": "Ali Ozgun", "orcid": "0000-0002-3198-7763", "clpid": "Konca-Ali-Ozgun" } ], "thesis_advisor": [ { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" } ], "thesis_committee": [ { "family_name": "Tromp", "given_name": "Jeroen", "clpid": "Tromp-J" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Simons", "given_name": "Mark", "clpid": "Simons-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis presents detailed studies of 4 large earthquakes. The 2006 Mw 8.6 Nias-Simeulue earthquake and 2007 Sumatra Mw 8.4 and 7.9 earthquake sequence which occurred on the Mentawai Island area of Sunda megathrust are studied using teleseismic, long period, GPS, and field data. Two crustal earthquakes, the 2005 Mw 7.6 Kashmir and the 1999 Mw 7.1 Duzce earthquakes, are studied using satellite image cross-correlation, seismic, GPS and SAR data.
\r\n\r\nThe 2005, Mw 8.6, Nias-Simeulue earthquake was caused by rupture of a portion of the Sunda megathrust offshore northern Sumatra. Based on the excitation of the normal modes and geodetic data, we put relatively tight constrains on the seismic moment and the fault dip, where the dip is determined to be 8o to10o with corresponding moments of 1.24 x 1022 to 1.00 x 1022 Nm, respectively. The geodetic constraints on slip distribution help to eliminate the trade-off between rupture velocity and slip kinematics. Our results indicate a relatively slow average rupture velocity of 1.5 to 2.5 km/s and long average rise time of up to 20 s.
\r\n\r\nOur study of the 2007 Mentawai Islands earthquakes shows the influence of permanent barriers on the extent of large megathrust ruptures, which can be a cause of some regularity of the seismic behavior, but also 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 arises mostly from the influence of nonpermanent barriers, probably zones with locally lower prestress due to the past earthquakes. The state of stress on that portion of the Sumatra megathrust was not adequate for the development of a single major large rupture at the time of this seismic crisis. However, the slip deficit that has accumulated since the 1833 and 1797 events remains large, and so is the potential for a large megahrust event in the Mentawai area.
\r\n\r\nWe analyzed the rupture process of 1999 Mw 7.1 Duzce earthquake using geodetic and seismic data. Applying subpixel cross-correlation of SPOT images acquired before and after the event, we mapped a continuous fault trace over 55 km; 15 km longer than the field reports. We investigated the spatiotemporal evolution of the earthquake using four-segment fault geometry with constraints on surface offsets based on satellite imagery, incorporated GPS and InSAR data and four strong-motion stations in the vicinity of the rupture. Our joint modeling shows a very stable slip distribution that does not depend on constraints imposed on rupture velocity. We show that no constant rupture velocity can explain the strong-motion data. Due to constraints from fault geometry and geodetic data, the rupture velocity has to vary rapidly. The rupture starts slow, accelerates to supershear speeds toward east and subsequently slows down. Supershear rupture is local and only toward the east of the hypocenter. Teleseismic data are consistent with the joint near-field model when 2 s time shifts are applied to their hand-picked arrivals. This implies that the weak beginning of the earthquake is not observable at teleseismic distances. This appears to be a common problem with teleseismic modeling and leads to more compact models with major slip around the hypocenter than the actual phenomenon. We performed teleseismic inversion models comparing four-segment fault geometry based on satellite imagery to one-segment geometry based on CMT solution. The four-segment model gives better predictions of near-field ground motions.
\r\n\r\nWe analyzed the Mw 7.6 Kashmir earthquake of October 8, 2005, using sub-pixel correlation of ASTER images to measure ground deformation, and modeling SAR imagery data along with seismic waveforms. The surface rupture is continuous over a distance of 75 km. The rupture lasted about 25 s and propagated up-dip and bilaterally by ~2 km/s, with a rise time of 2-5 s. The shallowness and compactness of the rupture, both in time and space, provide an explanation for the intensity of destructions. By comparing the teleseismic models with SAR data, we infer that satellite image correlation puts constraints on teleseismic models, which lead to more coherent models with the geodetic data. This kind of satellite image analysis could be achieved as soon as a postearthquake image is available, and would provide key information for early assessment of damages.
", "doi": "10.7907/6B13-4M30", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:1881", "collection": "thesis", "collection_id": "1881", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05192008-161405", "primary_object_url": { "basename": "Sebastien_Leprince_PhD_Thesis_2008.pdf", "content": "final", "filesize": 37994806, "license": "other", "mime_type": "application/pdf", "url": "/1881/1/Sebastien_Leprince_PhD_Thesis_2008.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Monitoring Earth Surface Dynamics with Optical Imagery", "author": [ { "family_name": "Leprince", "given_name": "Sebastien", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-Sebastien" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Elachi", "given_name": "Charles", "clpid": "Elachi-C" }, { "family_name": "Simons", "given_name": "Mark", "clpid": "Simons-M" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Despite the increasing availability of high-quality optical satellite images, continuous monitoring of Earth's surface changes is still of limited use due to technical limitations. To overcome these limitations, this thesis presents a processing chain to accurately orthorectify and co-register sets of satellite and aerial images, which, associated with a precise correlation technique, allow for the measurement of horizontal ground deformations with accuracy better than 1/10 of the pixel size. The irregular resampling problem is addressed to avoid introducing aliasing in the orthorectified images. Image registration and correlation is achieved with an iterative, unbiased processor that estimates the phase plane in the Fourier domain for sub-pixel shift detection. Errors due to the imaging system are calibrated and modeled, topography artifacts are characterized and solutions are proposed to compensate or to filter them.
\r\n\r\nA software package implementing these procedures, Co-registration of Optically Sensed Images and Correlation (COSI-Corr), is available from the Caltech Tectonics Observatory website. The procedure is validated in several different contexts, and applied to seismo-tectonics and glaciology studies.
\r\n\r\nAccurate measurements of horizontal co-seismic displacements in the near fault zone allow unambiguous imaging of surface ruptures. It is shown that measurements of surface ruptures from optical aerial and satellite images compare well with field measurements, and that in addition they have the potential of densely measuring the fault perpendicular component, and the off-fault distributed slip. When combined with seismic waveform modeling, fault geometry and surface offsets add crucial constraints to describe in details the seismic faulting process.
\r\n\r\nDense maps of glacier velocity are reported for several glaciers in Europe and in the Himalayas. Optical image correlation proves robust even in challenging mountainous areas, allowing accurate measurements of glacier flow velocity. Seasonal variations of glacier flow velocity are well identified, suggesting that such measurements can be used to better study the effects of climate change, and to refine the tuning of numerical glacier models.
", "doi": "10.7907/ZMTV-GV90", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" } ]