Planetary bodies experience deformation in response to tidal forces from external gravitating objects. Changes to planetary gravity fields produced by this forcing depend on internal rheological structure. For example, a spherically symmetric body's response to tides depends on the presence, thicknesses, and effective shear moduli of internal layers (e.g., the core, an ocean) and follows the spatial pattern of driving gravitational potentials. However, bodies that exhibit substantial deviation from spherical symmetry can exhibit a more complicated response to forcing that includes power both at short (i.e., regional-scale) and long (i.e., global-scale) wavelengths. In this thesis, we explore the impact of lateral heterogeneities in internal rheological structure on the tidal responses of Enceladus, the second major moon of Saturn, and Earth's Moon.
\r\n\r\nWe begin by exploring the impact of faults and lateral variations in ice shell thickness on the long-wavelength gravitational response of Enceladus (Chapter 2). Using finite element models of Enceladus' crust, we demonstrate substantial deviation between the longest-wavelength components of response to tidal forcing (i.e., the diurnal degree-2 Love numbers) and those expected for a spherically symmetric model of Enceladus. We further show that structural heterogeneities predominantly produce deformation over spatial scales similar to the size of these features. Based on this finding, we develop a methodology to precisely characterize regional variations in crustal thickness using local observations of surface strain at Enceladus (Chapter 3). We demonstrate that this strain can be readily inferred using measurements of the motion of the surface over the tidal cycle (e.g., via interferometric synthetic aperture radar or InSAR). We then adapt our finite element models to explore relationships between slip on fault structures over Enceladus' south polar region (i.e., the Tiger Stripes) and geological activity observed for the body (Chapter 4). We find a close correspondence between the double-peaked and asymmetric timing of strike-slip motion and observed diurnal variations in the brightness of a large plume emanating from Encealdus' South Pole. Based on this finding, we suggest that rifts along the Tiger Stripes experience periodic localized extension to modulate cryovolcanic activity. Finally, we use observations of the spherical harmonic degree-3 variability in the lunar gravity field to infer the presence of a 2-3% internal hemispheric, near-to-far- side variation in shear modulus of the Moon's mantle (Chapter 5). We demonstrate that a 100-200K hemispheric difference in mantle temperature can explain this inferred shear modulus structure, and suggest that internal asymmetries may be a remnant of processes which formed surface mare basalts ~4 Gya. Our work demonstrates future potential for the use of tidal tomography to characterize the deep interior structure and geodynamics of planetary bodies throughout the solar system.
", "doi": "10.7907/8b21-dj47", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:16254", "collection": "thesis", "collection_id": "16254", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11302023-021244845", "primary_object_url": { "basename": "Hightower_2024_Thesis.pdf", "content": "final", "filesize": 38506605, "license": "other", "mime_type": "application/pdf", "url": "/16254/1/Hightower_2024_Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "From Tectonic Evolution to Intraplate Stress: The Role of Structural Inheritance and Long-Wavelength Loading", "author": [ { "family_name": "Hightower", "given_name": "Erin Jessica", "orcid": "0000-0002-4734-5159", "clpid": "Hightower-Erin-Jessica" } ], "thesis_advisor": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Watkins", "given_name": "Michael M.", "clpid": "Watkins-M-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this thesis, I present a multifaceted exploration of various aspects of deformation and stress in the Earth's lithosphere using a variety of methods in a range of tectonic environments. I begin by examining the evolution of a young subduction zone through a combination of gravity modeling and seismological observations. Chapter 2 details the development a linear 3-D gravity inversion method capable of modelling complex geological regions such as subduction margins. Our procedure inverts satellite gravity to determine the best-fitting differential densities of spatially discretized subsurface prisms in a least-squares sense. We use a Bayesian approach to incorporate both data error and prior constraints based on seismic reflection and refraction data. Based on these data, Gaussian priors are applied to the appropriate model parameters as absolute equality constraints. To stabilize the inversion and provide relative equality constraints on the parameters, we utilize a combination of first and second order Tikhonov regularization, which enforces smoothness in the horizontal direction between seismically constrained regions, while allowing for sharper contacts in the vertical. We apply this method to the nascent Puysegur Trench, south of New Zealand, where oceanic lithosphere of the Australian Plate has under-thrust Puysegur Ridge and Solander Basin on the Pacific Plate since the Miocene. These models provide insight into the density contrasts, Moho depth, and crustal thickness in the region. The final model has a mean standard deviation on the model parameters of about 17 kg/m-3, and a mean absolute error on the predicted gravity of about 3.9 mGal, demonstrating the success of this method for even complex density distributions like those present at subduction zones. The posterior density distribution versus seismic velocity is diagnostic of compositional and structural changes and shows a thin sliver of oceanic crust emplaced between the nascent thrust and the strike slip Puysegur Fault. However, the northern end of the Puysegur Ridge, at the Snares Zone, is predominantly buoyant continental crust, despite its subsidence with respect to the rest of the ridge. These features highlight the mechanical changes unfolding during subduction initiation.
Chapter 3 explores the earthquake interevent time distribution. Earthquakes are commonly assumed to result from a stationary Poisson (SIP) process. We reassess the validity of this assumption using the Quake Template Matching (QTM) catalog and the relocated SCSN catalog (HYS) for Southern California. We analyze the interevent time (IET) distribution and the Schuster spectra after declustering with the Zaliapin and Ben Zion (2013) method. Both catalogs exhibit fat-tails on the IET distribution, deviating from the expected exponential distribution. The Schuster spectra of the catalogs are also inconsistent with an SIP process. The QTM catalog shows a statistically significant seasonal signal and a drift in the Schuster probability at long periods, likely due to increased seismicity following the 2010 El Mayor-Cucapah earthquake. This increase is also evident in the yearly IET distributions of the catalog. In contrast, the HYS Schuster spectrum does not show seasonality, but the yearly IET distributions exhibit a decrease in seismicity rate over the duration of the catalog, likely due to seismic network upgrades around 1990. We use synthetic catalogs to test the origin and significance of the observed deviations from the Poisson model. Variations in the QTM annual seismicity rate, around 5.6%, are too small to generate a noticeable departure from an exponential distribution, and the SIP model can not be rejected at the 5% significance level. The synthetic catalogs also suggest the fat-tail is an artefact of incomplete declustering. Overall, variations in the IET distribution for southern California are probably the result of both 1) incomplete declustering and location uncertainty, and 2) transient non-stationarity of the background rate from viscoelastic effects of large earthquakes. However, the stationary Poisson model appears adequate for describing background seismicity at the scale of Southern California and the decadal time scale of the QTM catalog.
Chapters 4 and 5 cover the primary focus of this thesis, exploring the influence of long-wavelength loading on the stress field of continental interiors and intraplate seismicity. The continental interior of eastern North America in particular has hosted many significant historical earthquakes and is undergoing both glacial isostatic adjustment (GIA) and long-wavelength subsidence due to the sinking of the Farallon slab. The regional seismicity concentrates within ancient failed rift arms and other paleo-tectonic structures, which can act as weak zones in the crust where stress accumulates. Within some of these zones, focal mechanism stress inversion shows significant rotational deviation of the maximum horizontal stress (SHmax) direction from the regional NE-SW trend, which may be explained by long-wavelength stress perturbations in the presence of lithospheric weakness. We focus on two sources of intraplate stress perturbation and seismicity and test the hypotheses that 1) mantle-flow induced epeirogenic subsidence and 2) GIA contribute to intraplate seismicity in eastern North America via reactivation of pre-existing faults.
For the slab loading component of this work, we use high-resolution global, spherical finite-element flow models with CitcomS. To capture realistic temperature fields and the Farallon slab, we convert seismic tomography models to temperature using a mineralogically constrained depth-dependent scaling factor. We utilize laterally variable temperature-dependent viscosities, upon which we superimpose low-viscosity plate boundary weak zones, as well as lithospheric intraplate weak zones at the locations of failed rifts and other inherited structures in eastern North America. We parameterize the Farallon slab in terms of its buoyancy to determine the degree to which the flow induced by the sinking slab contributes to intraplate stress. Using the modeled stress tensors from instantaneous flow calculations, we compute SHmax, the stress magnitudes, and the Coulomb failure stress on mapped faults in several major seismic zones. Slab sinking drives localized mantle flow beneath the central-eastern U.S., leading to a stress amplification of 100-150 MPa across the region that peaks over the New Madrid Seismic Zone. This stress amplification introduces a pronounced continent-wide clockwise rotation of the predicted SHmax direction, reaching as much as 20\u00b0 in some seismic zones, particularly when lithospheric weak zones are included. In the New Madrid, Central Virginia, Charlevoix, and Lower Saint Lawrence Seismic Zones, the presence of weak zones loaded by the Farallon slab at depth can explain the pattern of clockwise rotation of the observed focal mechanism derived SHmax relative to the regional borehole derived SHmax as reported in previous studies. However, misfits on SHmax within many of the major seismic zones suggest other sources of stress are needed to properly reproduce the observed stress trends in some areas. We also find that in order for pre-existing lithospheric weak zones to exert appreciable control on intraplate stress under the influence of mantle flow, they must be shallow/sub-crustal and in contact with the crust. These stress perturbations and rotations ultimately bring faults in the NMSZ, the Western Quebec Seismic Zone (WQSZ), and the Lower Saint Lawrence and Charlevoix Seismic Zones closer to failure. In particular, inclusion of the Farallon slab and weak zones produces positive Coulomb failure stresses on some key faults associated with major historical earthquakes, including the Reelfoot Fault in the NMSZ and the Timiskaming fault in the WQSZ. Fault instability is even more likely when assuming weaker faults with lower coefficients of friction.
For the glacial unloading component of this work, we use the global, spherical finite element code CitcomSVE, which models dynamic deformation of a viscoelastic and incompressible planetary mantle in response to surface loading. We supply CitcomSVE with the same seismically constrained viscosity structures computed in the CitcomS models, including those with weak zones, and load the Earth model with the ICE-6G ice history. We perform the same suite of simulations and stress analyses as in the mantle loading problem, using the stress tensor output of the corresponding CitcomS model as the tectonic background stress. We compare the mantle flow and GIA induced stresses, with focus on the present day extant glacially derived stress field. GIA induced stress perturbations are small (~10 MPa), even in the presence of lithospheric weak zones. GIA induced SHmax alone exhibits a transition from clockwise to counterclockwise rotation moving northeast across the continent. We find that only by inclusion of the mantle flow derived background stress can we reproduce the continental scale clockwise stress rotation observed in stress data, suggesting the effect of mantle loading is more important for explaining these observations than is GIA. In the NMSZ, GIA helps promote stability on the Reelfoot Fault, in opposition to mantle flow, while promoting instability on more non-optimally oriented faults. GIA also helps localize higher Coulomb failure stress within the Charlevoix Seismic Zone and the western half of the WQSZ. In the WQSZ and LSLRS, GIA stress perturbations are large enough that even with only a small reduction in the coefficient of friction, faults that are not likely to fail under the background tectonic and geodynamic stresses alone could slip. Further investigation of the sensitivity of GIA stress to different 3D and 1D viscosity structures and the change in GIA stress with time since deglaciation is warranted to better understand how GIA affects intraplate seismicity. Ultimately, constraining how mantle flow and GIA affect stress and deformation in the presence of laterally variable viscosity is integral to quantifying how long-wavelength loading may alter the spatial distribution of seismic hazard.
", "doi": "10.7907/xc1b-ke51", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16449", "collection": "thesis", "collection_id": "16449", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302024-182513713", "primary_object_url": { "basename": "Li_Yida_PhD_thesis_final.pdf", "content": "final", "filesize": 68106313, "license": "other", "mime_type": "application/pdf", "url": "/16449/1/Li_Yida_PhD_thesis_final.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "I. Dynamics of Subduction Initiation and II. Constraining Sedimentary Basin Structure with Seismic Ambient Noise", "author": [ { "family_name": "Li", "given_name": "Yida", "orcid": "0000-0003-0664-0247", "clpid": "Li-Yida" } ], "thesis_advisor": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Ross", "given_name": "Zachary E.", "orcid": "0000-0002-6343-8400", "clpid": "Ross-Z-E" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "Seismological Laboratory" }, { "literal": "div_gps" } ], "abstract": "Subduction initiation, the inception of a subduction zone, heralds dramatic changes in tectonic plate kinematics and dynamics. In the first half of the thesis, I focus on understanding the dynamics of the subduction initiation process through a synthesis of numerical computations and theoretical frameworks. In Chapter 2, we employ force balance analysis and 2D geodynamic models to yield an analytical solution on the force evolution of the subducting plate. This formulation illuminates a pivotal phase in subduction initiation \u2014- the compression-to-extension transition of plate forces -\u2014 as a defining milestone. In Chapter 3, we extend this analytical framework into a sliced 3D context (2.5D) while incorporating the influence of strike-slip motion. Modified from Chapter 2, the analytical solution validates that strike-slip motion facilitates subduction initiation by accelerating the process of weakening. Chapter 4 ventures into 3D geodynamic modeling, focusing on the Puysegur trench -\u2014 a living example of subduction initiation. The models demonstrate a capability to match multiple geophysical and geological observations quantitatively with mechanical models. With a parametric search, we discover the best-fitting models require a relatively fast strain weakening rate, which can be explained by pore-pressure weakening at shallow depths and grain-size reduction at greater depths.
\r\n \r\n \r\nThe second part of this thesis transitions to ambient seismic noise correlation. In Chapter 5, we conduct an ambient noise tomography in northern Los Angeles basins with a newly obtained, dense seismic data set. The new shear wave velocity model exhibits a lower velocity in the basins than previous community models, which can potentially resolve the inconsistency between observed and calculated ground motions. In Chapter 6, we introduce a new method to identify the near-field noise sources from the spurious arrivals in ambient noise correlations. The correlation between the inverted noise sources and geological features in northern LA basins suggests the viability of this technique as a novel means of identifying geological structures, including faults.
", "doi": "10.7907/y3z2-z538", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:13961", "collection": "thesis", "collection_id": "13961", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09212020-084147468", "type": "thesis", "title": "Provenance, Structural Geology, and Sedimentation of the Miocene and Pliocene Californias", "author": [ { "family_name": "Sabbeth", "given_name": "Leah", "orcid": "0000-0001-6615-7949", "clpid": "Sabbeth-Leah" } ], "thesis_advisor": [ { "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" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Bucholz", "given_name": "Claire E.", "orcid": "0000-0003-3252-7109", "clpid": "Bucholz-C-E" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The first chapter of this thesis documents a provenance study, in which orthoquartzite clasts deposited in the Miocene Sespe Formation are linked to the Mesoproterozoic Shinumo Quartzite. The Sespe Formation outcrops in the Santa Monica Mountains and the Santa Ana Mountains, both in California. The Shinumo Quartzite outcrops only in Grand Canyon. We determine that the Shinumo Quartzite can be distinguished from other sources that may feed the Sespe Formation through its unique combination of a moderate paleomagnetic inclination and 1.2, 1.4, and 1.7 Ga detrital zircon spectrum peaks. This provenance link places an important constraint on the drainage of a paleo-Colorado River from Grand Canyon during Miocene time.
\r\n\r\nThe second and third chapters of this thesis are hinged upon a geologic mapping project on Isla \u00c1ngel de la Guarda, a microcontinental block, in Baja California, Mexico. A plate reorganization at the end of the late Miocene andesitic arc marks the transfer of Baja California and the not-yet-rifted Isla \u00c1ngel de la Guarda to the Pacific plate from the North American plate. Between 3 and 2 Ma, the plate boundary jumped again, northward along the Ballenas Transform fault. In this Pliocene time, units mapped in this study were deposited.
\r\n\r\nThe oldest units mapped are Miocene-Pliocene volcanic flows, for which we have no lower age constraint. The oldest volcanic flow dated is a Pliocene andesite lava (3.916 \u00b1 0.088 Ma from 40Ar/39Ar). We map Miocene to Pliocene volcanic flows and Pliocene to Quaternary sedimentary units in two field areas. The sedimentary units are probably results of Pliocene rifting-related basin subsidence. Geochemical data from X-ray fluorescence indicate that lavas are compositionally similar to ~12 Ma arc-related rocks mapped in the Puertecitos Volcanic Province. In the southern field area, the sedimentary units are overlain by a Pliocene basaltic andesite with an 40Ar/39Ar age of 2.754 \u00b1 0.021 Ma. We map several NNE-striking faults throughout both field areas, which cut NNW-striking bedding in Pliocene units. The Pliocene volcanic flows and sedimentary units were probably tilted before faulting, and the faults are likely linked to the Northern Salsipuedes Basin, offshore of the island in the Ballenas Channel. Both of these events may be results of 3-2 Ma rifting.
", "doi": "10.7907/gbcs-9289", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:11344", "collection": "thesis", "collection_id": "11344", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01172019-113222535", "primary_object_url": { "basename": "witkosky_rebecca_thesis_2019.pdf", "content": "final", "filesize": 19923162, "license": "other", "mime_type": "application/pdf", "url": "/11344/38/witkosky_rebecca_thesis_2019.pdf", "version": "v10.0.0" }, "type": "thesis", "title": "Tectonics in Nevada and Southern California: Subsidence of the Ediacaran Johnnie Formation, Cumulative Offset Along the Lavic Lake Fault, and Geomorphic Surface Development Along the Southern San Andreas Fault", "author": [ { "family_name": "Witkosky", "given_name": "Rebecca Amber", "clpid": "Witkosky-Rebecca-Amber" } ], "thesis_advisor": [ { "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" } ], "thesis_committee": [ { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "While we know the ages and tectonic histories of many critical geologic events in the history of the Earth, there are still questions regarding the timing of key events and structures that have and continue to influence life on this planet. This thesis includes three separate studies in Nevada and southern California: two potential new methods for measuring/organizing geologic time, and also an analysis of the long-term displacement along an active fault in the eastern California shear zone. In Chapter II, we used tectonic subsidence modeling to find that the Shuram carbon isotopic excursion in the Ediacaran Johnnie Formation likely occurred from 585-579 Ma, and that incision of the Rainstorm Member shelf occurred during the 579 Ma Gaskiers glaciation. The pre-Shuram-excursion chemostratigraphic carbon isotope profiles from the Khufai Formation in Oman and the type locality of the Johnnie Formation in Nevada are both generally positive and therefore possibly correlative. In Chapter III, we determined the cumulative tectonic offset along the Lavic Lake fault, an active structure that ruptured with >5 m of coseismic slip in the 1999 Mw 7.1 Hector Mine earthquake. We calculated a net slip of 960 +70/-40 m, based on the slip vector formed by a vertically separated lithologic contact and a horizontally separated older cross fault. The net slip we calculated is significantly less than a previous estimate that was based on an offset magnetic gradient, a disparity that may be explained by considering off-fault deformation, as well as the unknown depth and nature of the source of the magnetic contrast. In Chapter IV, we explored using a new method for the relative dating of Quaternary geomorphic surfaces, which is based on the positive correlation between increased spectral contrast in thermal hyperspectral airborne imagery and surface age. With field data, we found that desert varnish scores, desert pavement scores, and vegetation spacing estimates also correlate positively with surface age, implying that these factors could contribute to the increased spectral contrast in airborne remote sensing spectra. Additionally, the general increase in the band depth of airborne spectra at 9.16 \u03bcm could be due to increasing clay mineral abundance in progressively heavier desert varnish coatings on older surfaces. The positive correlation observed in this study between surface age and spectral contrast in airborne spectra can perhaps be used to develop a method for relative dating of varnished geomorphic surfaces elsewhere. All of the chapters in this thesis are broadly related by the concepts of geologic time and tectonic activity, which are two aspects of modern geology that are intrinsic to the science as a whole.
", "doi": "10.7907/XTZX-X107", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:10827", "collection": "thesis", "collection_id": "10827", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04222018-154136913", "primary_object_url": { "basename": "Bowden_Thesis2018.pdf", "content": "final", "filesize": 8829130, "license": "other", "mime_type": "application/pdf", "url": "/10827/1/Bowden_Thesis2018.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Propagation and Amplification of Surface Waves", "author": [ { "family_name": "Bowden", "given_name": "Daniel Craig", "orcid": "0000-0003-3332-5146", "clpid": "Bowden-Daniel-Craig" } ], "thesis_advisor": [ { "family_name": "Tsai", "given_name": "Victor C.", "orcid": "0000-0003-1809-6672", "clpid": "Tsai-V-C" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Tsai", "given_name": "Victor C.", "orcid": "0000-0003-1809-6672", "clpid": "Tsai-V-C" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Heaton", "given_name": "Thomas H.", "orcid": "0000-0003-3363-2197", "clpid": "Heaton-T-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The observation of surface waves from cross-correlations of ambient noise has proven to be an invaluable tool for the recovery of seismic travel times. Such techniques allow the construction of 3D velocity models and subsequent geologic interpretations in regions where tomography would otherwise be difficult due to the paucity of seismicity and short seismic array deployment times. One such model is developed here for offshore southern California using an array of Ocean Bottom Seismometers to better understand the tectonic history of the region.
\r\n\r\nHowever, for accurate hazard evaluation, characterizations of the spatial variability of ground motion amplitudes are also desired. Unfortunately, the amplitudes from noise cross-correlations are systematically biased by the spatial-, frequency- and temporal variability of noise sources. We demonstrate in this thesis that an ambient-noise based wavefront tracking technique using an array of stations can recover site-amplification and attenuation estimates successfully and robustly. This is applied on two different scales: to a very dense array of more than 5,000 geophones in the city of Long Beach, CA, and in a broader, continental scale to instruments from the USArray.
\r\n\r\nFinally, we discuss the propagation of surface waves in relation to seismic hazard and site characterization. We point out that the amplitude response and peak frequency of ground motion will be different for a given site, depending on the type of wave being considered. This work should be considered by any future seismic hazard evaluation where surface waves may cause damage.
\r\n", "doi": "10.7907/Z9DR2SPR", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10953", "collection": "thesis", "collection_id": "10953", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282018-115947263", "primary_object_url": { "basename": "Daven-Quinn-thesis-2018.pdf", "content": "final", "filesize": 155896431, "license": "other", "mime_type": "application/pdf", "url": "/10953/9/Daven-Quinn-thesis-2018.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Regional Structural Geology of Earth and Mars", "author": [ { "family_name": "Quinn", "given_name": "Daven Patel", "orcid": "0000-0003-1895-3742", "clpid": "Quinn-Daven-Patel" } ], "thesis_advisor": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "This thesis explores the geologic context around several key environmental transitions on Earth and Mars which are expressed at continental margins. Regional mapping techniques are applied to build links between methodologies used to explore rock samples and units \u2014 stratigraphy, structural geology, remote sensing, geochemistry, petrology, and geodynamic modeling. Four research projects are presented: Chapter 2 explores the tectonic context of xenoliths beneath the western margin of North America and illuminates the structural history of the lithospheric underpinnings of the California coast. In Chapter 3, we undertake a structural study of the southern Naukluft Mountains, Namibia, and re-interpret its tectonic context and age. Chapter 4 builds a new method for applying statistical errors to remotely measured planar orientations, and Chapter 5 applies this method to mapping the 3D structure of a globally significant stratigraphy on Mars. We find a long history of interaction with water at the margin of Isidis Basin. Together, these projects demonstrate the application of structural techniques to continental margins on Earth and Mars, and the creation of new techniques to support geological analysis from remotely-sensed data, where structural measurements may be poorly resolved.", "doi": "10.7907/9enj-wn23", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10171", "collection": "thesis", "collection_id": "10171", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05142017-011958758", "type": "thesis", "title": "I: Normal Faulting on the Austroalpine \u2018Overthrust\u2019 Constrained by Thermochronometry and Kinematic Analysis, Central Alps, Graub\u00fcnden Region, Switzerland. II: Clumped Isotope Thermometry of Carbonate Phases Associated with the Copper Deposits of Kennecott, Alaska", "author": [ { "family_name": "Price", "given_name": "Jason Brian", "orcid": "0000-0001-9865-603X", "clpid": "Price-Jason-Brian" } ], "thesis_advisor": [ { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "I. A compilation of 362 cooling ages, including 52 newly reported in this study, from nine thermochronometric systems, 40K/39Ar amphibole, 40K/39Ar white mica, 87Rb/86Sr white mica, 40K/39Ar biotite, 87Rb/86Sr biotite, zircon and apatite fission track, zircon and apatite (U-Th)/He, indicate that the base of the Austroalpine allochthonous \u2018orogenic lid\u2019 was not in full thermal equilibrium with its Penninic substrate until at least the middle Oligocene, approximately 29-28 Ma, to allowably as late as the early Miocene, ca. 18 Ma. There is about a factor-of-five difference in cooling rates between the hanging wall (ca. 4\u00b0C/m.y.) and footwall (ca. 20\u00b0C/m.y.) during this period. In addition, there are demonstrably higher metamorphic grades, including blueschist- and eclogite-facies, in the Pennine footwall compared to lower greenschist-facies in the Austroalpine hanging wall. Together these two facts demonstrate that hot, high-pressure Penninic nappes were forced upward against the cold, low-pressure overriding Austroalpine plate in a very short time window of approximately 7-10 m.y. between the time of peak metamorphism during the Eocene and the time of thermal equilibration with the overriding plate during the Oligo-Miocene. The most likely mechanism to produce such a cold-on-hot juxtaposition is a normal fault, and therefore, we conclude that an important period of nappe emplacement in the Central Swiss Alps occurred concurrently with orogen-perpendicular normal fault motion at the base of the Austroalpine allochthon persisting well into the Oligocene and possibly into the early Miocene, post-dating the 32-30 Ma age of the Bergell intrusion.
\r\n\r\nMesoscopic structural measurements made at the top and bottom of the Pennine zone in eastern Switzerland indicate multiple, spatially heterogeneous directions of movement. At the top, in the Oberhalbstein Valley, movement directions vary from dominantly top-east to top-south-southeast a very minor top-north component within Pennine rocks of the Martegnas shear zone and no preferred movement direction within the Austroalpine hanging wall. Near Piz Toissa, a minimum of two kilometers of nearby structural section in the Err and Platta nappes have been faulted out. At the bottom of the Pennine zone in Val Lumnezia and the Chur Rhein Valley at Trimmis, we observe top-northwest, top-north, and top-northeast movements. In Val Lumnezia, the Sub-Penninic Scopi zone (Gotthard cover rocks) shows movement in a top-northwest direction; the superjacent Peidener imbricate fault zone, a relatively thin (ca. 50 to 100 m thick) structural zone consisting of Scopi zone lithologies, shows movement in a northeasterly direction; above that, the basal Penninic B\u00fcndnerschiefer shows no dominant movement direction. To the east, in the Chur Rhine Valley, movement is well defined as exclusively top-north. Therefore, movement directions in the lower B\u00fcndnerschiefer are broadly top-north but heterogeneous in direction along strike between Val Lumnezia and Chur Rhein Valley, and, as first suggested by Weh and Frotizheim (2001), it may be erroneous to regard the basal Pennine thrust as a simple through-going structure. In Val Lumnezia, the Scopi-Peidener-Pennine nappes resemble a \u201cjelly sandwich\u201d in which the thick Pennine mass utilized the Peidener zone to move in an oblique sinistral-normal slip sense past the southeast-dipping allochthonous Scopi zone and its east-dipping Gotthard \u201cmassif\u201d substrate. If the Peidener zone continues northeastward beneath alluvial cover of the Chur Rhein Valley, it may serve as a late, NE-directed shear zone that separates the Pennine nappes from European units. If so, it would explain the apparent truncation and progressive omission of allochthonous elements of European affinity along the zone from southwest to northeast beneath alluvium of the Chur Rhein Valley. We therefore infer that the direct juxtaposition of Penninic units to the east with the Helvetic autochthon to the west at the latitude of Trimmis records an episode of top-northeast, orogen-parallel strike-slip and extensional movement.
\r\n\r\nZircon (U-Th)/He (ZHe) cooling ages from the Oberhalbstein Valley indicate that the Austroalpine-Pennine contact was still active at ca. 27 Ma, and that the Martegnas shear zone was active, in part, between ca. 27 and 24 Ma. It is likely that the Piz Toissa klippe formed around this time during the late Oligocene. The pattern of much younger ZHe ages at the bottom of the Pennine zone is independent of any nappe boundaries, including the Peidener imbricate fault zone, but is consistent with the rise of the Aar massif during the Miocene. Tectonic movements, as recorded by the mesostructure in the Austroalpine, Penninic, and Sub-Penninic domains, and local ZHe cooling ages generally support the conclusion drawn strictly from cooling ages that the Pennine zone was emplaced en masse as a coherent \u2018piston\u2019 or \u2018mega-pip\u2019 during Oligocene to early Miocene time (approximately 29 to 18 Ma), well after juxtaposition of Apulia with cratonic Europe (continent-continent collision) and during the development of Alpine topography and the peripheral basins (viz. Molasse and Lombardi). Additional top-north movement and late uplift and flexure of the nappe stack, along with the Aar massif, occurred primarily in middle to upper Miocene time, following the post-collisional structural interposition of the Pennine zone between Europe and Apulia.
\r\n\r\nII. Nine carbonate phases at Kennecott, Alaska were measured for their clumped isotope (\u220647) equilibration temperatures. The total range for carbonate temperatures spans 38-164\u00b0C. Premineral phases are relatively cool (43-71\u00b0C); synmineral phases are relatively warm (89-157\u00b0C); late postmineral phases are the most cool (38-59\u00b0C) but overlap some premineral phases. Zebra dolomite precipitated in the range 130-163\u00b0C. Dedolomite, a hallmark alteration feature of the mineralizing fluids, falls into a narrow range of 98-109\u00b0C, consistent with the stability field for the low-temperature chalcocite polymorph. Except for one sample, none of the synmineral calcites crystallized within the stability field of djurleite, a volumetrically significant component of the main-stage ore, which suggests that intergrown djurleite may have been a somewhat later recrystallization product of chalcocite rather than a coeval phase.
\r\n\r\nCalculated compositions for \u03b418Owater vary from -4.2 to +11.0\u2030. The most depleted water precipitated hydrothermal baroque dolomite, whereas the most enriched water was associated with recrystallized limestone wallrock on the periphery of the orebody. Waters that precipitated calcite+copper vary from -1.1 to +9.3\u2030.
\r\n\r\nIntriguingly, rhythmic layering in zebra dolomite can be resolved in \u220647 space, and preliminary data indicate that the coarser-grained baroque dolomite bands precipitated at temperatures 5-10\u00b0C cooler than the surrounding, finer-grained dolomite wall rock bands.
\r\n\r\nThe calculated values of \u03b418Owater support a genetic model that invokes redox changes associated with fluid mixing as the likely mechanism responsible for copper deposition. In this model a sulfidic, basinal fluid having \u03b418O similar to seawater mixes with a cuprous fluid having heavier \u03b418O (5 to 8\u2030) which was derived from the Nikolai Greenstone during prehnite-pumpellyite-facies metamorphism.
", "doi": "10.7907/Z9JM27NJ", "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:9748", "collection": "thesis", "collection_id": "9748", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05252016-090108907", "type": "thesis", "title": "Tectonics of Central and Eastern California, Late Cretaceous to Modern", "author": [ { "family_name": "Sousa", "given_name": "Francis Joseph", "orcid": "0000-0003-1623-4023", "clpid": "Sousa-Francis-Joseph" } ], "thesis_advisor": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" } ], "local_group": [ { "literal": "Seismological Laboratory" }, { "literal": "div_gps" } ], "abstract": "The Late Cretaceous to Modern tectonic evolution of central and eastern California has been studied for many decades, with published work generally focusing on specific geographic areas and time periods. The resulting literature leaves the reader, whether graduate student, faculty member, or layperson, wondering what a coherently integrated tectonic evolution might look like, or if it would be at all possible to undertake such a task. This question is the common thread weaving together the four studies presented in this work. Each of the individual chapters is targeted at a specific location and time period which I have identified as a critical yet missing link in piecing together a coherent regional tectonic story. In the first chapter, we re-discover a set of major west down normal faults running along the western slope of the southern Sierra, the western Sierra fault system (WSFS). We show that one of these faults was offset by roughly a kilometer in Eocene time, and that this activity directly resulted in the incision of much of the relief present in modern Kings Canyon. The second chapter is a basement landscape and thermochronometric study of the hanging wall of the WSFS. New data from this study area provide a significant westward expansion of basement thermochronometric data from the southern Sierra Nevada batholith. Thermal modeling results of these data provide critical new constraints on the early exhumation of the Sierra Nevada batholith, and in the context of the results from Chapter I, allow us to piece together a coherent chronology of tectonic forcings and landscape evolution for the southern Sierra Nevada. In the third chapter, I present a study of the surface rupture of the 1999 Hector Mine earthquake, a dextral strike slip event on a fault in the Eastern California Shear Zone (ECSZ). New constraints on the active tectonics in ECSZ will help future studies better resolve the enigmatic mismatch between geologic slip rates and geodetically determined regional rates. Chapter IV is a magnetostratigraphic pilot study of the Paleocene Goler Formation. This study provides strong evidence that continued investigation will yield new constraints on the depositional age of the only fossil-bearing Paleocene terrestrial deposit on the west coast of North America. Each of these studies aims to provide important new data at critical missing links in the tectonic evolution of central and eastern California.", "doi": "10.7907/Z9H41PD8", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9748", "collection": "thesis", "collection_id": "9748", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05252016-090108907", "type": "thesis", "title": "Tectonics of Central and Eastern California, Late Cretaceous to Modern", "author": [ { "family_name": "Sousa", "given_name": "Francis Joseph", "orcid": "0000-0003-1623-4023", "clpid": "Sousa-Francis-Joseph" } ], "thesis_advisor": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" } ], "local_group": [ { "literal": "Seismological Laboratory" }, { "literal": "div_gps" } ], "abstract": "The Late Cretaceous to Modern tectonic evolution of central and eastern California has been studied for many decades, with published work generally focusing on specific geographic areas and time periods. The resulting literature leaves the reader, whether graduate student, faculty member, or layperson, wondering what a coherently integrated tectonic evolution might look like, or if it would be at all possible to undertake such a task. This question is the common thread weaving together the four studies presented in this work. Each of the individual chapters is targeted at a specific location and time period which I have identified as a critical yet missing link in piecing together a coherent regional tectonic story. In the first chapter, we re-discover a set of major west down normal faults running along the western slope of the southern Sierra, the western Sierra fault system (WSFS). We show that one of these faults was offset by roughly a kilometer in Eocene time, and that this activity directly resulted in the incision of much of the relief present in modern Kings Canyon. The second chapter is a basement landscape and thermochronometric study of the hanging wall of the WSFS. New data from this study area provide a significant westward expansion of basement thermochronometric data from the southern Sierra Nevada batholith. Thermal modeling results of these data provide critical new constraints on the early exhumation of the Sierra Nevada batholith, and in the context of the results from Chapter I, allow us to piece together a coherent chronology of tectonic forcings and landscape evolution for the southern Sierra Nevada. In the third chapter, I present a study of the surface rupture of the 1999 Hector Mine earthquake, a dextral strike slip event on a fault in the Eastern California Shear Zone (ECSZ). New constraints on the active tectonics in ECSZ will help future studies better resolve the enigmatic mismatch between geologic slip rates and geodetically determined regional rates. Chapter IV is a magnetostratigraphic pilot study of the Paleocene Goler Formation. This study provides strong evidence that continued investigation will yield new constraints on the depositional age of the only fossil-bearing Paleocene terrestrial deposit on the west coast of North America. Each of these studies aims to provide important new data at critical missing links in the tectonic evolution of central and eastern California.", "doi": "10.7907/Z9H41PD8", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9334", "collection": "thesis", "collection_id": "9334", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12192015-004219343", "primary_object_url": { "basename": "Ma_Yiran_2016_thesis.pdf", "content": "final", "filesize": 35588498, "license": "other", "mime_type": "application/pdf", "url": "/9334/1/Ma_Yiran_2016_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Imaging the Earth with Ambient Noise and Earthquakes", "author": [ { "family_name": "Ma", "given_name": "Yiran", "orcid": "0000-0002-8369-3310", "clpid": "Ma-Yiran" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "thesis_committee": [ { "family_name": "Tsai", "given_name": "Victor C.", "orcid": "0000-0003-1809-6672", "clpid": "Tsai-V-C" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Jackson", "given_name": "Jennifer M.", "orcid": "0000-0002-8256-6336", "clpid": "Jackson-J-M" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this thesis, I develop the velocity and structure models for the Los Angeles Basin and Southern Peru. The ultimate goal is to better understand the geological processes involved in the basin and subduction zone dynamics. The results are obtained from seismic interferometry using ambient noise and receiver functions using earthquake- generated waves. Some unusual signals specific to the local structures are also studied. The main findings are summarized as follows:The fine-scale seismic structure of the central Mexico, southern Peru, and southwest Japan subduction zones is studied using intraslab earthquakes recorded by temporary and permanent regional seismic arrays. The morphology of the transition from flat to normal subduction is explored in central Mexico and southern Peru, while in southwest Japan the spatial coincidence of a thin ultra-slow velocity layer (USL) atop the flat slab with locations of slow slip events (SSEs) is explored. This USL is also observed in central Mexico and southern Peru, where its lateral extent is used as one constraint on the nature of the flat-to-normal transitions.
\r\n\r\nIn western central Mexico, I find an edge to this USL which is coincident with the western boundary of the projected Orozco Fracture Zone (OFZ) region. Forward modeling of the 2D structure of the subducted Cocos plate using a finite-difference algorithm provides constraints on the velocity and geometry of the slab\u2019s seismic structure in this region and confirms the location of the USL edge. I propose that the Cocos slab is currently fragmenting into a North Cocos plate and a South Cocos plate along the projection of the OFZ, by a process analogous to that which occurred when the Rivera plate separated from the proto-Cocos plate 10 Ma.
\r\n\r\nIn eastern central Mexico, observations of a sharp transition in slab dip near the abrupt end of the Trans Mexican Volcanic Belt (TMVB) suggest a possible slab tear located within the subducted South Cocos plate. The eastern lateral extent of the USL is found to be coincident with these features and with the western boundary of a zone of decreased seismicity, indicating a change in structure which I interpret as evidence of a possible tear. Analysis of intraslab seismicity patterns and focal mechanism orientations and faulting types provides further support for a possible tear in the South Cocos slab. This potential tear, together with the tear along the projection of the OFZ to the northwest, indicates a slab rollback mechanism in which separate slab segments move independently, allowing for mantle flow between the segments.
\r\n\r\nIn southern Peru, observations of a gradual increase in slab dip coupled with a lack of any gaps or vertical offsets in the intraslab seismicity suggest a smooth contortion of the slab. Concentrations of focal mechanisms at orientations which are indicative of slab bending are also observed along the change in slab geometry. The lateral extent of the USL atop the horizontal Nazca slab is found to be coincident with the margin of the projected linear continuation of the subducting Nazca Ridge, implying a causal relationship, but not a slab tear. Waveform modeling of the 2D structure in southern Peru provides constraints on the velocity and geometry of the slab\u2019s seismic structure and confirms the absence of any tears in the slab.
\r\n\r\nIn southwest Japan, I estimate the location of a possible USL along the Philippine Sea slab surface and find this region of low velocity to be coincident with locations of SSEs that have occurred in this region. I interpret the source of the possible USL in this region as fluids dehydrated from the subducting plate, forming a high pore-fluid pressure layer, which would be expected to decrease the coupling on the plate interface and promote SSEs.
", "doi": "10.7907/WHSR-VY75", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:8429", "collection": "thesis", "collection_id": "8429", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05292014-181733885", "primary_object_url": { "basename": "Dougherty_Sara_2014_thesis_full.pdf", "content": "final", "filesize": 17157794, "license": "other", "mime_type": "application/pdf", "url": "/8429/37/Dougherty_Sara_2014_thesis_full.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Seismic Structure along Transitions from Flat to Normal Subduction: Central Mexico, Southern Peru, and Southwest Japan", "author": [ { "family_name": "Dougherty", "given_name": "Sara Lyn", "orcid": "0000-0002-5327-3286", "clpid": "Dougherty-Sara-Lyn" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" } ], "thesis_committee": [ { "family_name": "Jackson", "given_name": "Jennifer M.", "orcid": "0000-0002-8256-6336", "clpid": "Jackson-J-M" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The fine-scale seismic structure of the central Mexico, southern Peru, and southwest Japan subduction zones is studied using intraslab earthquakes recorded by temporary and permanent regional seismic arrays. The morphology of the transition from flat to normal subduction is explored in central Mexico and southern Peru, while in southwest Japan the spatial coincidence of a thin ultra-slow velocity layer (USL) atop the flat slab with locations of slow slip events (SSEs) is explored. This USL is also observed in central Mexico and southern Peru, where its lateral extent is used as one constraint on the nature of the flat-to-normal transitions.
\r\n\r\nIn western central Mexico, I find an edge to this USL which is coincident with the western boundary of the projected Orozco Fracture Zone (OFZ) region. Forward modeling of the 2D structure of the subducted Cocos plate using a finite-difference algorithm provides constraints on the velocity and geometry of the slab\u2019s seismic structure in this region and confirms the location of the USL edge. I propose that the Cocos slab is currently fragmenting into a North Cocos plate and a South Cocos plate along the projection of the OFZ, by a process analogous to that which occurred when the Rivera plate separated from the proto-Cocos plate 10 Ma.
\r\n\r\nIn eastern central Mexico, observations of a sharp transition in slab dip near the abrupt end of the Trans Mexican Volcanic Belt (TMVB) suggest a possible slab tear located within the subducted South Cocos plate. The eastern lateral extent of the USL is found to be coincident with these features and with the western boundary of a zone of decreased seismicity, indicating a change in structure which I interpret as evidence of a possible tear. Analysis of intraslab seismicity patterns and focal mechanism orientations and faulting types provides further support for a possible tear in the South Cocos slab. This potential tear, together with the tear along the projection of the OFZ to the northwest, indicates a slab rollback mechanism in which separate slab segments move independently, allowing for mantle flow between the segments.
\r\n\r\nIn southern Peru, observations of a gradual increase in slab dip coupled with a lack of any gaps or vertical offsets in the intraslab seismicity suggest a smooth contortion of the slab. Concentrations of focal mechanisms at orientations which are indicative of slab bending are also observed along the change in slab geometry. The lateral extent of the USL atop the horizontal Nazca slab is found to be coincident with the margin of the projected linear continuation of the subducting Nazca Ridge, implying a causal relationship, but not a slab tear. Waveform modeling of the 2D structure in southern Peru provides constraints on the velocity and geometry of the slab\u2019s seismic structure and confirms the absence of any tears in the slab.
\r\n\r\nIn southwest Japan, I estimate the location of a possible USL along the Philippine Sea slab surface and find this region of low velocity to be coincident with locations of SSEs that have occurred in this region. I interpret the source of the possible USL in this region as fluids dehydrated from the subducting plate, forming a high pore-fluid pressure layer, which would be expected to decrease the coupling on the plate interface and promote SSEs.
", "doi": "10.7907/WHSR-VY75", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "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: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:7300", "collection": "thesis", "collection_id": "7300", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11302012-163616170", "primary_object_url": { "basename": "thesis_kphillipsalonge.pdf", "content": "final", "filesize": 34121059, "license": "other", "mime_type": "application/pdf", "url": "/7300/1/thesis_kphillipsalonge.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Structure of the Subduction System in Southern Peru from Seismic Array Data", "author": [ { "family_name": "Phillips-Alonge", "given_name": "Kristin Eileen", "clpid": "Phillips-Kristin-Eileen" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "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" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Southern Peru represents a subduction transition region from normal subduction in the southernmost part of Peru to flat slab subduction in central Peru. In order to learn more about the structure of southern Peru, causes of flat slab subduction, and the nature of the transition from normal to flat slab subduction, we installed three seismic arrays utilizing a total of about 100 broadband stations. The first installed array samples the normal subduction region, while the second samples the transition from normal to flat subduction, and the third samples the flat slab region near where the Nazca Ridge is presently subducting. Data from teleseismic events greater than 30 degrees distance from Peru was analyzed using the receiver function method that makes use of P to S converted phases at interfaces such as the Moho to provide information about the structure directly beneath each station. A strong signal from the Moho was observed for each array and was found to have a maximum depth of around 75 km beneath the Altiplano. The average crustal Vp/Vs ratio was also estimated and was found to have an average value of around 1.75 beneath the Altiplano. The shape of the slab was also clarified for the three arrays. The transition from normal to flat slab subduction appears to be a contortion rather than a break in the slab. In addition to those signals, a positive impedance midcrustal signal at about 40 km depth was widely observed for stations on the eastern side of the arrays. The midcrustal signal is indicative of a velocity increase in the lower crust and is suggested to be an observation of the underthrusting Brazilian shield which would have implications for the timing of uplift in the Andes. Finite difference modeling with velocity models that include a midcrustal structure produces synthetics which are consistent with receiver function observations. Receiver function results and other related methods provide a simple way of making direct observations of key structural interfaces and the current state of the subduction system which has relevance in studies of the tectonic evolution of the region and estimations of causes of flat slab subduction.", "doi": "10.7907/71A7-4211", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7191", "collection": "thesis", "collection_id": "7191", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08232012-003426663", "primary_object_url": { "basename": "Meng-Lingsen_2013.pdf", "content": "final", "filesize": 6137558, "license": "other", "mime_type": "application/pdf", "url": "/7191/6/Meng-Lingsen_2013.pdf", "version": "v9.0.0" }, "type": "thesis", "title": "Navigating Earthquake Physics with High-Resolution Array Back-Projection", "author": [ { "family_name": "Meng", "given_name": "Lingsen", "clpid": "Meng-Lingsen" } ], "thesis_advisor": [ { "family_name": "Ampuero", "given_name": "Jean-Paul", "orcid": "0000-0002-4827-7987", "clpid": "Ampuero-J-P" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-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" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Understanding earthquake source dynamics is a fundamental goal of geophysics. Progress toward this goal has been slow due to the gap between state-of-art earthquake simulations and the limited source imaging techniques based on conventional low-frequency finite fault inversions. Seismic array processing is an alternative source imaging technique that employs the higher frequency content of the earthquakes and provides finer detail of the source process with few prior assumptions. While the back-projection provides key observations of previous large earthquakes, the standard beamforming back-projection suffers from low resolution and severe artifacts. This thesis introduces the MUSIC technique, a high-resolution array processing method that aims to narrow the gap between the seismic observations and earthquake simulations.
\r\n\r\nThe MUSIC is a high-resolution method taking advantage of the higher order signal statistics. The method has not been widely used in seismology yet because of the nonstationary and incoherent nature of the seismic signal. We adapt MUSIC to transient seismic signal by incorporating the Multitaper cross-spectrum estimates. We also adopt a \u201creference window\u201d strategy that mitigates the \u201cswimming artifact,\u201d a systematic drift effect in back projection. The improved MUSIC back projections allow the imaging of recent large earthquakes in finer details which give rise to new perspectives on dynamic simulations. In the 2011 Tohoku-Oki earthquake, we observe frequency-dependent rupture behaviors which relate to the material variation along the dip of the subduction interface. In the 2012 off-Sumatra earthquake, we image the complicated ruptures involving orthogonal fault system and an usual branching direction. This result along with our complementary dynamic simulations probes the pressure-insensitive strength of the deep oceanic lithosphere. In another example, back projection is applied to the 2010 M7 Haiti earthquake recorded at regional distance. The high-frequency subevents are located at the edges of geodetic slip regions, which are correlated to the stopping phases associated with rupture speed reduction when the earthquake arrests.
", "doi": "10.7907/Y2C6-YA15", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7854", "collection": "thesis", "collection_id": "7854", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06062013-151342444", "type": "thesis", "title": "Plate Tectonic Constraints on Flat Subduction and Paleomagnetic Constraints on Rifting", "author": [ { "family_name": "Skinner", "given_name": "Steven Michael", "clpid": "Skinner-Steven-Michael" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Plate tectonics shapes our dynamic planet through the creation and destruction of lithosphere. This work focuses on increasing our understanding of the processes at convergent and divergent boundaries through geologic and geophysical observations at modern plate boundaries. Recent work had shown that the subducting slab in central Mexico is most likely the flattest on Earth, yet there was no consensus about what caused it to originate. The first chapter of this thesis sets out to systematically test all previously proposed mechanisms for slab flattening on the Mexican case. What we have discovered is that there is only one model for which we can find no contradictory evidence. The lack of applicability of the standard mechanisms used to explain flat subduction in the Mexican example led us to question their applications globally. The second chapter expands the search for a cause of flat subduction, in both space and time. We focus on the historical record of flat slabs in South America and look for a correlation between the shallowing and steepening of slab segments with relation to the inferred thickness of the subducting oceanic crust. Using plate reconstructions and the assumption that a crustal anomaly formed on a spreading ridge will produce two conjugate features, we recreate the history of subduction along the South American margin and find that there is no correlation between the subduction of a bathymetric highs and shallow subduction. These studies have proven that a subducting crustal anomaly is neither a sufficient or necessary condition of flat slab subduction. The final chapter in this thesis looks at the divergent plate boundary in the Gulf of California. Through geologic reconnaissance mapping and an intensive paleomagnetic sampling campaign, we try to constrain the location and orientation of a widespread volcanic marker unit, the Tuff of San Felipe. Although the resolution of the applied magnetic susceptibility technique proved inadequate to contain the direction of the pyroclastic flow with high precision, we have been able to detect the tectonic rotation of coherent blocks as well as rotation within blocks.", "doi": "10.7907/G94S-Z109", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7197", "collection": "thesis", "collection_id": "7197", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09052012-110119932", "primary_object_url": { "basename": "Williams_Nneka_Thesis_Final_Version.pdf", "content": "final", "filesize": 19415536, "license": "other", "mime_type": "application/pdf", "url": "/7197/1/Williams_Nneka_Thesis_Final_Version.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Defining the Relationship between Seismicity and Deformation at Regional and Local Scales", "author": [ { "family_name": "Williams", "given_name": "Nneka Njeri Akosua", "clpid": "Williams-Nneka-Njeri-Akosua" } ], "thesis_advisor": [ { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" } ], "thesis_committee": [ { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Heaton", "given_name": "Thomas H.", "orcid": "0000-0003-3363-2197", "clpid": "Heaton-T-H" }, { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this thesis, I use source inversion methods to improve understanding of crustal deformation along the Nyainquentanglha (NQTL) Detachment in Southern Tibet and the Piceance Basin in northwestern Colorado. Broadband station coverage in both regions is sparse, necessitating the development of innovative approaches to source inversion for the purpose of studying local earthquakes.
\r\n\r\nIn an effort to study the 2002-2003 earthquake swarm and the 2008 Mw 6.3 Damxung earthquake and aftershocks that occurred in the NQTL region, we developed a single station earthquake location inversion method called the SP Envelope method, to be used with data from LHSA at Lhasa, a broadband seismometer located 75 km away. A location is calculated by first rotating the seismogram until the azimuth at which the envelope of the P-wave arrival on the T-component is smallest (its great circle path) is found. The distance at which to place the location along this azimuth is measured by calculating the S-P distance from arrivals on the seismogram. When used in conjunction with an existing waveform modeling based source inversion method called Cut and Paste (CAP), a catalog of 40 regional earthquakes was generated.
\r\n\r\nFrom these 40 earthquakes, a catalog of 30 earthquakes with the most certain locations was generated to study the relationship of seismicity and NQTL region faults mapped in Google Earth and in Armijo et al., 1986 and Kapp et al., 2005. Using these faults and focal mechanisms, a fault model of the NQTL Region was generated using GOCAD, a 3D modeling suite. By studying the relationship of modeled faults to mapped fault traces at the surface, the most likely fault slip plane was chosen. These fault planes were then used to calculate slip vectors and a regional bulk stress tensor, with respect to which the low-angle NQTL Detachment was found to be badly misoriented. The formation of low-angle normal faults is inconsistent with the Anderson Theory of faulting, and the presence of the NQTL Detachment in a region with such an incongruous stress field supports the notion that such faults are real.
\r\n\r\nThe timing and locations of the earthquakes in this catalog with respect to an anomalous increase in the eastward component of velocity readings at the single cGPS station in Lhasa (LHAS) were analyzed to determine the relationship between plastic and brittle deformation in the region. The fact that cGPS velocities slow significantly after the 2002-2003 earthquake swarm suggests that this motion is tectonic in nature, and it has been interpreted as only the second continental slow slip event (SSE) ever to be observed. The observation of slow slip followed by an earthquake swarm within a Tibetan rift suggests that other swarms observed within similar rifts in the region are related to SSEs.
\r\n\r\nIn the Piceance Basin, CAP was used to determine source mechanisms of microearthquakes triggered as a result of fracture stimulation within a tight gas reservoir. The expense of drilling monitor wells and installing borehole geophones reduces the azimuthal station coverage, thus making it difficult to determine source mechanisms of microearthquakes using more traditional methods. For high signal to noise ratio records, CAP produced results on par with those obtained in studies of regional earthquakes. This finding suggests that CAP could successfully be applied in studies of microseismicity when data quality is high.
", "doi": "10.7907/CN29-YV40", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7854", "collection": "thesis", "collection_id": "7854", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06062013-151342444", "type": "thesis", "title": "Plate Tectonic Constraints on Flat Subduction and Paleomagnetic Constraints on Rifting", "author": [ { "family_name": "Skinner", "given_name": "Steven Michael", "clpid": "Skinner-Steven-Michael" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Plate tectonics shapes our dynamic planet through the creation and destruction of lithosphere. This work focuses on increasing our understanding of the processes at convergent and divergent boundaries through geologic and geophysical observations at modern plate boundaries. Recent work had shown that the subducting slab in central Mexico is most likely the flattest on Earth, yet there was no consensus about what caused it to originate. The first chapter of this thesis sets out to systematically test all previously proposed mechanisms for slab flattening on the Mexican case. What we have discovered is that there is only one model for which we can find no contradictory evidence. The lack of applicability of the standard mechanisms used to explain flat subduction in the Mexican example led us to question their applications globally. The second chapter expands the search for a cause of flat subduction, in both space and time. We focus on the historical record of flat slabs in South America and look for a correlation between the shallowing and steepening of slab segments with relation to the inferred thickness of the subducting oceanic crust. Using plate reconstructions and the assumption that a crustal anomaly formed on a spreading ridge will produce two conjugate features, we recreate the history of subduction along the South American margin and find that there is no correlation between the subduction of a bathymetric highs and shallow subduction. These studies have proven that a subducting crustal anomaly is neither a sufficient or necessary condition of flat slab subduction. The final chapter in this thesis looks at the divergent plate boundary in the Gulf of California. Through geologic reconnaissance mapping and an intensive paleomagnetic sampling campaign, we try to constrain the location and orientation of a widespread volcanic marker unit, the Tuff of San Felipe. Although the resolution of the applied magnetic susceptibility technique proved inadequate to contain the direction of the pyroclastic flow with high precision, we have been able to detect the tectonic rotation of coherent blocks as well as rotation within blocks.", "doi": "10.7907/G94S-Z109", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7862", "collection": "thesis", "collection_id": "7862", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072013-083424637", "primary_object_url": { "basename": "Edgar_Thesis_2013.pdf", "content": "final", "filesize": 121967803, "license": "other", "mime_type": "application/pdf", "url": "/7862/1/Edgar_Thesis_2013.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Identifying and Interpreting Stratification in Sedimentary Rocks on Mars: Insight from Rover and Orbital Observations and Terrestrial Field Analogs", "author": [ { "family_name": "Edgar", "given_name": "Lauren Ashley", "clpid": "Edgar-Lauren-Ashley" } ], "thesis_advisor": [ { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "thesis_committee": [ { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Sedimentary rocks on Mars provide insight into past aqueous and atmospheric processes, climate regimes, and potential habitability. The stratigraphic architecture of sedimentary rocks on Mars is similar to that of Earth, indicating that the processes that govern deposition and erosion on Mars can be reasonably inferred through reference to analogous terrestrial systems. This dissertation aims to understand Martian surface processes through the use of (1) ground-based observations from the Mars Exploration Rovers, (2) orbital data from the High Resolution Imaging Science Experiment onboard the Mars Reconnaissance Orbiter, and (3) the use of terrestrial field analogs to understand bedforms and sediment transport on Mars. Chapters 1 and 2 trace the history of aqueous activity at Meridiani Planum, through the reconstruction of eolian bedforms at Victoria crater, and the identification of a potential mudstone facies at Santa Maria crater. Chapter 3 uses Terrestrial Laser Scanning to study cross-bedding in pyroclastic surge deposits on Earth in order to understand sediment transport in these events and to establish criteria for their identification on Mars. The final chapter analyzes stratal geometries in the Martian North Polar Layered Deposits using tools for sequence stratigraphic analysis, to better constrain past surface processes and past climate conditions on Mars.", "doi": "10.7907/RAGV-WT91", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "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:6544", "collection": "thesis", "collection_id": "6544", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07212011-115223871", "primary_object_url": { "basename": "Chapman_2011_thesis.pdf", "content": "final", "filesize": 39218300, "license": "other", "mime_type": "application/pdf", "url": "/6544/1/Chapman_2011_thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Late Cretaceous Gravitational Collapse of the Southern Sierra Nevada Batholith and Adjacent Areas Above Underplated Schists, Southern California", "author": [ { "family_name": "Chapman", "given_name": "Alan Daniel", "clpid": "Chapman-Alan-Daniel" } ], "thesis_advisor": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" } ], "thesis_committee": [ { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 \u00b0N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swing up to 90\u02da westward, taking on an east-west trend; 3) western zone rocks are truncated by eastern zone rocks along the proto-Kern Canyon fault, a Late Cretaceous oblique ductile thrust; and 4) fragments of shallow-level eastern SNB affinity rocks overlie deeper-level western zone rocks and subjacent subduction accretion assemblages (Rand, San Emigdio, and Sierra de Salinas schists) along a major Late Cretaceous detachment system. Integration of these observations with new and existing data reveals a temporal relationship between schist unroofing and upper crustal extension and rotation. I present a model whereby Late Cretaceous shallow subduction and subsequent trench-directed channelized extrusion of the schist triggered gravitational collapse of the overlying crustal column. This overarching model is based on several investigations summarized below.
\r\n\r\nThermobarometry, thermodynamic modelling and garnet diffusion modelling are presented that elucidate the tectonics of subduction and eduction of the San Emigdio Schist. I document an upsection increase in peak temperature (i.e. inverted metamorphism), from 590 to 700 \u00b0C, peak pressures ranging from 8.5 to 11.1 kbar, limited partial melting, microstructural evidence for large seismic events, rapid cooling (825\u2013380 \u00b0C/Myr) from peak conditions and an \u201cout and back\u201d P\u2013T path. Progressive cooling and tectonic underplating beneath an initially hot upper plate following the onset of shallow subduction provide a working hypothesis explaining high temperatures, inverted metamorphism, partial melting, and the observed P\u2013T trajectory calculated from the San Emigdio body.
\r\n\r\nNew geologic mapping and microstructural analysis indicate that the schist was transported to the SSW during structural ascent along a mylonitic contact (the Rand fault and Salinas shear zone) with upper plate assemblages. Crystallographic preferred orientation patterns in deformed quartzites reveal a decreasing simple shear component with increasing structural depth, suggesting a pure shear-dominated westward flow within the subduction channel and localized simple shear along the upper channel boundary. The resulting flow type within the channel is that of general shear extrusion.
\r\n\r\nStructural, thermobarometric, U-Pb geochronologic, and geochemical data from plutonic and metamorphic framework assemblages in the southern SNB also suggest SSW-directed transport of upper plate(s) along a major Late Cretaceous detachment system. The timing and pattern of regional dispersion of crustal fragments in the southern SNB is most consistent with Late Cretaceous collapse above the underplated schist. These observations imply a high degree of coupling between the shallow and deep crust during high magnitude extension. Zircon (U-Th)/He data presented herein reveal a rapid cooling event at 77 \u00b1 5 Ma, probably reflecting the time of large magnitude detachment faulting. A comparison of this dataset with existing apatite (U-Th)/He thermochronometry suggests that the development of modern landscape and arrangement of tectonic elements in southern California was greatly preconditioned by Late Cretaceous tectonics.
\r\n\r\nFinally, detrital and metamorphic zircon of the structurally highest and earliest subducted portions of the San Emigdio Schist constrain the depositional age to between ca. 102 and 98 Ma. Zircon oxygen isotope data from both lower plate schist and upper plate batholithic assemblages reveal a \u03b418O shift of ~ 1.5\u2030 between igneous (~ 5.5\u2030) and metamorphic (~ 7\u2030) domains. These results, taken with previous zircon and whole-rock \u03b418O measurements, provide evidence for massive devolatilization of the San Emigdio Schist and fluid traversal of upper plate batholithic assemblages, thereby altering the isotopic composition of overlying material. Furthermore, the timing of fluid-rock interaction in the southwestern SNB is coincident with eastward arc migration and an associated pulse of voluminous magmatism. I posit that during flattening of the Farallon slab the schist was rapidly delivered to the magmatic source, where ensuing devolatilization triggered a magmatic flare-up in the southeastern SNB. This short-lived (less than 15 Myr) high-flux event was followed by the termination of arc magmatism as the shallow subduction zone approached thermal equilibrium.
", "doi": "10.7907/NAQX-Y886", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6870", "collection": "thesis", "collection_id": "6870", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03262012-175814763", "primary_object_url": { "basename": "TChenThesis.pdf", "content": "final", "filesize": 13489798, "license": "other", "mime_type": "application/pdf", "url": "/6870/1/TChenThesis.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Part I: Structure of Central and Southern Mexico from Velocity and Attenuation Tomography. Part II: Physics of Small Repeating Earthquakes ", "author": [ { "family_name": "Chen", "given_name": "Ting", "clpid": "Chen-Ting" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In part I, the 3D velocity and attenuation structure of the Cocos subduction zone in Mexico is imaged using earthquakes recorded by two temporary seismic arrays and local stations. Inversion results reveal low-attenuation and high-velocity Cocos slab. The slab dip angle increases from almost flat in central Mexico near Mexico City to about 30 degrees in southern Mexico near the Isthmus of Tehuantepec. High attenuation and low velocity in the crust beneath the Trans-Mexico Volcanic Belt correlate with low resistivity, and are probably related to dehydration and melting process. The most pronounced high-attenuation, low-Vp and high-Vp/Vs anomaly is found in the crust beneath the Veracruz Basin. A high-velocity structure dipping southward from the Gulf of Mexico near the Isthmus of Tehuantepec coincides with a discontinuity from a receiver functions study, and provides an evidence for the collision between the Yucatan Block and Mexico in the Miocene.
\r\n\r\n\r\nIn part II, we show that a model of small repeating earthquakes based on laboratory-derived rate and state friction laws reproduces the observed scaling between the recurrence time and seismic moment. In the model, a small fault patch governed by velocity-weakening friction is surrounded by a much larger velocity-strengthening region. For a fixed set of friction parameters, the observed scaling is reproduced by varying the size of the velocity-weakening patch. We further investigate the behavior of small repeating earthquakes in related models under different scenarios, including several forms of the state evolution equations in rate- and state-dependent friction laws, rectangular velocity-weakening patch geometries, quasi-dynamic vs. fully dynamic representation of inertial effects, and 2D vs. 3D simulations. We find that the simulated scalings between the recurrence time and seismic moment for these different scenarios are similar while differences do exist. We propose a theoretical model for the scaling between the recurrence time and seismic moment of small repeating earthquakes. The obtained theoretical insight is used to find the combinations of fault properties that allow the model to fit the observed scaling and range of the seismic moment and recurrence time.
", "doi": "10.7907/REJW-YJ88", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "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:6440", "collection": "thesis", "collection_id": "6440", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05252011-161906788", "primary_object_url": { "basename": "Selvans2011_Thesis.pdf", "content": "final", "filesize": 26866733, "license": "other", "mime_type": "application/pdf", "url": "/6440/1/Selvans2011_Thesis.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Geophysical Investigations of Near-Surface Structure on the Earth and Mars", "author": [ { "family_name": "Selvans", "given_name": "Michelle Marie", "clpid": "Selvans-Michelle-Marie" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Aharonson", "given_name": "Oded", "orcid": "0000-0001-9930-2495", "clpid": "Aharonson-O" }, { "family_name": "Plaut", "given_name": "Jeffrey J.", "orcid": "0000-0002-5367-1188", "clpid": "Plaut-J-J" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "I use remote sensing and active seismic methods to investigate near-surface structure on the Earth and Mars. These studies provide insight into styles of crustal deformation acting on continental margins in regions of extension, as well as paleoclimates that shaped the polar ice caps on Mars. I map the overall structure of the ice-rich Planum Boreum deposit at the north pole of Mars using 178 orbits of Mars Advanced Radar for Subsurface and Ionosphere Sounding data, and find no deflection of the lithosphere beneath the ice load. Bright, laterally extensive subsurface reflectors in the radargrams define the surface underlying Planum Boreum, as well as the interface between the two main units, the stratigraphically older Basal Unit and the stratigraphically younger North Polar Layered Deposits. The volumes of these units, and the overall edifice, are determined to the greatest accuracy possible to date. On Earth, I use a GPS campaign network in the state of Jalisco to investigate tectonic motion and interseismic deformation in the area. The consistent magnitude and direction of station velocities on the Jalisco Block suggest that it is moving rigidly with respect to North America. We constrain extension across the bounding fault zones of the block to values that are slow compared to relative rates of motion at nearby plate boundaries. I study another continental rift zone, in the Ross Sea, Antarctica, with refraction seismic data collected during research cruise NBP0701. I construct velocity models from 71 sonobuoys that detect deep structure in the oceanic crust of the Adare Basin and the crust of the Northern Basin, which lies to the south on the continental shelf. We demonstrate the importance of using multi-channel seismic data to correct for ocean currents and changes in ship navigation, the finite-difference modeling techniques necessary for accurately determining 1D velocity profiles for each sonobuoy, and for tying true velocities to the multi-channel seismic images of subsurface structure. We construct 2D velocity profiles using widely spaced sonobuoys in the Adare Basin, and using overlapping sonobuoys along some lines in both basins, and across the shelf break, to investigate crustal structure in the region. Detection of the Moho at 5.5 km below the seafloor by one sonobuoy suggests relatively thin oceanic crust in the Adare Basin, and flat velocity contours across the margin suggest continuity in crustal structure between the two basins.", "doi": "10.7907/078P-0C05", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6361", "collection": "thesis", "collection_id": "6361", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04272011-150709139", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 15539995, "license": "other", "mime_type": "application/pdf", "url": "/6361/1/thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Properties of the Subduction System in Mexico", "author": [ { "family_name": "Kim", "given_name": "YoungHee", "clpid": "Kim-YoungHee" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "thesis_committee": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Jackson", "given_name": "Jennifer M.", "orcid": "0000-0002-8256-6336", "clpid": "Jackson-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis presents seismic imaging results of the structure of the Mexican subduction zone using receiver function (RF) based on teleseismic P-to-S converted waves, in order to gain insight into the physical and chemical factors associated with internal geodynamic processes. More specifically, this thesis investigates (1) the nature of tectonic processes involved in the buildup and subsequent modification of continental and oceanic lithosphere, and (2) the determination of mineralogy/petrology and fluidphase\r\nreactions in the subducting Cocos oceanic crust.
\r\n\r\nUtilizing the data acquired from two dense broadband seismic lines in Mexico, the geometries and seismic properties of the interface of the subducting Cocos plate beneath Mexico are determined from the RFs. The RF image for central Mexico shows that the subducting oceanic crust dips shallowly north at 15 degrees for a distance of 80 km from Acapulco at the Pacific coast, and then horizontally underplates the continental crust for approximately 200 km to the Trans-Mexican Volcanic Belt (TMVB). Modeling of the RF conversion amplitudes and timings of the underplated features reveals a thin very-low velocity zone between the plate and the continental crust that appears to absorb nearly all of the strain between the upper plate and the slab. The migrated image of the RFs shows that the slab dips steeply into the mantle at an angle of about 75 degrees beneath the TMVB.
\r\n\r\nThe RF results for southern Mexico in the Isthmus of Tehuantepec show an image of the Cocos slab down to about 100 km depth. The same cross-section image also reveals a slab-like south-dipping structure interpreted to be subducted from the Gulf of Mexico. This anomalous slab with the opposite dip direction of the Cocos slab appears to cut off the Cocos slab at 150 km depth. There is no tectonic explanation for the south-dipping slab under the current paradigm of Caribbean plate reconstructions. We present in this thesis the case for a new reconstruction of the Gulf of Mexico and propose that the slab may be due to the collision of the Yucatan Block into Mexico in the Miocene, and may also be responsible for the Cocos plate truncation imaged from previous tomography studies. This hypothesis explains the Chiapas Fold and Thrust Belt to the south of the Yucatan Block and may explain the unusual volcanic arc configuration in southern Mexico.
\r\n\r\nWe formulate and apply a new inversion technique based on the plane wave conversion to obtain the seismic parameters (S wave velocity, Vs, and density) of the oceanic crust. We use such parameters to infer mineralogical properties of subducting oceanic crust. From this effort, we provide tighter constraints on physical properties of the subducting Cocos oceanic crust, and explain the difference in the slab geometries betweeen central and southern Mexico from the mineral physics point of view. Anomalously low Vs (2.4\u22123.4 km/s) in the upper part of the flat oceanic crust in central Mexico points to elevated Poisson\u2019s and Vp/Vs ratios of the oceanic crust. This directly relates to the presence of water and hydrous minerals or high pore pressure; the mechanically weak hydrous layer may explain current subduction geometry at very shallow depth of about 45 km without strong coupling between the plates.
\r\n\r\nUsing Vp/Vs as a function of Vs in a range of likely pressure and temperature for candidate hydrous phases, we identify the major hydrous mineral phases present in the upper (3\u22125 km thickness) and lower parts (3\u22125 km thickness) of the subducted oceanic crust of central and southern Mexico. In central Mexico, the upper oceanic crust in the flat slab region is enriched with hydrous minerals such as talc over the normal oceanic crustal compositions such as MORB-like gabbro. Petrologically, the generation of talc during subduction of the oceanic crust is nearly impossible. One possible mechanism to produce such a low-velocity anomaly at the upper oceanic crust is that lower crustal rocks are hydrated with 15-20 percent of free water to reduce the seismic velocities significantly. We thus propose that the thin low-velocity, talc-rich layer in the upper oceanic crust is then generated from the mantle wedge side during the slab flattening process coupled with trench rollback. The talc-rich rocks at the slab interface can be formed in the mantle by the addition of silica transported by rising fluids via the dehydration reaction from the subducting oceanic crust and by mechanical mixing of mantle and siliceous rocks. The evolution of the thin low-strength zone, which decouples the horizontal slab from the continental crust, originating from the mantle wedge side rather than the trench side, has important implications for the dynamics of the subduction system, including the flattening process of the slab, as well as the geochemistry of the mantle wedge and arc in central Mexico. After passing through the flat segment, the major compositions of the steeply subducting oceanic crust underneath the TMVB are zoisite and lawsonite from 60 to 100 km in depth. The eclogitization occurs at the depth of about 100 km. The dominant mineral phase in the upper oceanic crust of southern Mexico from 45 to 120 km depth is amphibole on top of unaltered gabbroic oceanic crust.
", "doi": "10.7907/BB7N-QP03", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5714", "collection": "thesis", "collection_id": "5714", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04102010-113856474", "primary_object_url": { "basename": "Metz_Thesis.pdf", "content": "final", "filesize": 13717555, "license": "other", "mime_type": "application/pdf", "url": "/5714/8/Metz_Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "A Study of the Record of Ancient Sedimentary Rocks on Mars Using MER, HiRISE and CRISM Images", "author": [ { "family_name": "Metz", "given_name": "Joannah Marie", "clpid": "Metz-Joannah-Marie" } ], "thesis_advisor": [ { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "thesis_committee": [ { "family_name": "Aharonson", "given_name": "Oded", "orcid": "0000-0001-9930-2495", "clpid": "Aharonson-O" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" }, { "family_name": "Milliken", "given_name": "Ralph E.", "clpid": "Milliken-R-E" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Many processes that operate on a planetary surface have the potential to create sedimentary deposits which when preserved as rocks can provide clues that allow past environmental conditions to be reconstructed. This work combines several studies using data from the Mars Exploration Rover and Mars Reconnaissance Orbiter spacecraft to examine the structure and sedimentology of the sedimentary rock record of Mars. The first study supports the dune-interdune model proposed for the formation of the deposits at the Opportunity landing site in Meridiani Planum and provides evidence that liquid water was involved to a greater extent in the formation of outcrops in Erebus crater. The next study identifies two depositional fan complexes on the floor of southwestern Melas Chasma and suggests that they may be sublacustrine in origin, which suggests the former presence of a significant body of water stable for at least 100 to 10,000 years. Furthermore, the basin containing the fans may be a complete source-to-sink system. The third study examines the geomorphic channel patterns present on analogue terrestrial submarine fans and deltas. The last study characterizes the extent and styles of deformation of sedimentary rocks in Valles Marineris and finds that subaerial or subaqueous gravitational slumping or sliding and soft-sediment deformation are potential mechanisms that may have caused the deformation.", "doi": "10.7907/8ZCD-SK38", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:5909", "collection": "thesis", "collection_id": "5909", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022010-172250027", "primary_object_url": { "basename": "Thesis_Liu_2010-total.pdf", "content": "final", "filesize": 8535268, "license": "other", "mime_type": "application/pdf", "url": "/5909/17/Thesis_Liu_2010-total.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Linking Surface Evolution with Mantle Dynamic Processes Using Adjoint Models with Data Assimilation", "author": [ { "family_name": "Liu", "given_name": "Lijun", "clpid": "Liu-Lijun" } ], "thesis_advisor": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Quantifying the relationship between subsolidus mantle convection and surface evolution is a fundamental goal of geophysics. Toward this goal progress has been slow due to incomplete knowledge of the earth\u2019s internal structure and properties. While seismic tomography reveals details on internal 3D structure of the present mantle, evolution of the subsolidus mantle during the geological past remains elusive. This thesis attempts to solve the time inversion of mantle convection using the adjoint method based on present-day seismic images and geological and geophysical observations dictating the past evolution of solid earth.
\r\n\r\nThe adjoint method, widely used in meteorological and oceanographic predictions, can be applied to mantle convection for the recovery of unknown initial conditions through the assimilation of present-day mantle seismic structure. We propose that an optimal first guess to the initial condition can be obtained through a simple backward integration (SBI) of the governing equations thus lessening the computational expense. By incorporating time-dependent surface dynamic topography in addition to present-day mantle structure, the adjoint method is improved so as to constrain uncertain mantle dynamic properties and initial condition simultaneously. The theory is derived from the governing equations of mantle convection and validated by synthetic experiments for a single- and two-layer viscosity mantle within regionally bounded spherical shells. For both cases, we show that the theory can constrain mantle properties with errors arising through the adjoint recovery of the initial condition. For the two-layer model, there is a trade-off between the temperature scaling and lower mantle viscosity.
\r\n\r\nBy assimilating seismic structure and plate motions in the inverse mantle convection model, we reconstruct Farallon plate subduction back to 100 Ma. We put constraints on basic mantle properties, including both the depth dependence of mantle viscosity and slab buoyancy, by predicting proxies of dynamic topography evident in the stratigraphy of the North American Cretaceous western interior seaway. Models that fit stratigraphy well require the Farallon slab to have been flat lying in the Late Cretaceous, consistent with geological reconstructions. The models predict an extensive zone of shallow-dipping subduction extending beyond the flat-lying slab farther east and north, while the limited region of subducting flat slab resembles an oceanic plateau. In order to test the hypothesis of oceanic plateau subduction and its relationship to the Laramide orogeny, we compare the inverse convection model with plate reconstructions. Two prominent seismic anomalies on the Farallon plate recovered from inverse models coincide with paleogeographically-restored positions of conjugates to the Shatsky and Hess plateaus when they subducted beneath North America. The distributed shortening of the Laramide orogeny closely tracked the passage of the Shatsky conjugate beneath North America, while the effects of Hess conjugate subduction were restricted to the northern Mexico foreland belt. We find that Laramide uplifts were consequences of the removal, rather than the emplacement, of the Shatsky conjugate, and we predict that these subducted plateaus should be detectable by the USArray seismic experiment.
\r\n\r\nThe inverse convection models predict a continuous vertical motion history of western U.S., which is further validated by constraints on the vertical motion of the Colorado Plateau since the Cretaceous. With the arrival of the flat-lying Farallon slab, dynamic subsidence swept from west to east over the western U.S., peaking at 86 Ma within the Colorado Plateau. This eastward migrating dynamic subsidence is consistent with a recently compiled backstripping study that shows a long-wavelength residual subsidence shifting to the east, coincident with the passage of the flat slab beneath North America in our inverse model. Two stages of uplift followed the removal of the Farallon slab below the Colorado Plateau: one in the latest Cretaceous, and the other in the Eocene, with a cumulative uplift of ~1.2 km; the former represents the Laramide uplift which also marks the initial uplift of the entire western U.S. Both the descent of the slab and buoyant upwellings raised the Colorado Plateau to its current elevation during the Oligocene. A locally thick lithosphere enhances coupling to the upper mantle so that the Colorado Plateau has a higher topography with sharp edges. Our models also predict that the plateau tilted downward to the northeast before the Oligocene, caused by northeast-trending subduction of the Farallon slab, and that this northeast tilting diminished and reversed to the southwest during the Miocene in response to buoyant upwellings.
\r\n\r\nOverall, this thesis shows that the adjoint models with data assimilation are useful in linking surface evolution to deep mantle processes both over North America and areas beyond. While more research is clearly needed to construct a more earth-like model, this thesis presents an important advance in data-oriented geodynamic models.
", "doi": "10.7907/6VHZ-V130", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:5909", "collection": "thesis", "collection_id": "5909", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022010-172250027", "primary_object_url": { "basename": "Thesis_Liu_2010-total.pdf", "content": "final", "filesize": 8535268, "license": "other", "mime_type": "application/pdf", "url": "/5909/17/Thesis_Liu_2010-total.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Linking Surface Evolution with Mantle Dynamic Processes Using Adjoint Models with Data Assimilation", "author": [ { "family_name": "Liu", "given_name": "Lijun", "clpid": "Liu-Lijun" } ], "thesis_advisor": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Quantifying the relationship between subsolidus mantle convection and surface evolution is a fundamental goal of geophysics. Toward this goal progress has been slow due to incomplete knowledge of the earth\u2019s internal structure and properties. While seismic tomography reveals details on internal 3D structure of the present mantle, evolution of the subsolidus mantle during the geological past remains elusive. This thesis attempts to solve the time inversion of mantle convection using the adjoint method based on present-day seismic images and geological and geophysical observations dictating the past evolution of solid earth.
\r\n\r\nThe adjoint method, widely used in meteorological and oceanographic predictions, can be applied to mantle convection for the recovery of unknown initial conditions through the assimilation of present-day mantle seismic structure. We propose that an optimal first guess to the initial condition can be obtained through a simple backward integration (SBI) of the governing equations thus lessening the computational expense. By incorporating time-dependent surface dynamic topography in addition to present-day mantle structure, the adjoint method is improved so as to constrain uncertain mantle dynamic properties and initial condition simultaneously. The theory is derived from the governing equations of mantle convection and validated by synthetic experiments for a single- and two-layer viscosity mantle within regionally bounded spherical shells. For both cases, we show that the theory can constrain mantle properties with errors arising through the adjoint recovery of the initial condition. For the two-layer model, there is a trade-off between the temperature scaling and lower mantle viscosity.
\r\n\r\nBy assimilating seismic structure and plate motions in the inverse mantle convection model, we reconstruct Farallon plate subduction back to 100 Ma. We put constraints on basic mantle properties, including both the depth dependence of mantle viscosity and slab buoyancy, by predicting proxies of dynamic topography evident in the stratigraphy of the North American Cretaceous western interior seaway. Models that fit stratigraphy well require the Farallon slab to have been flat lying in the Late Cretaceous, consistent with geological reconstructions. The models predict an extensive zone of shallow-dipping subduction extending beyond the flat-lying slab farther east and north, while the limited region of subducting flat slab resembles an oceanic plateau. In order to test the hypothesis of oceanic plateau subduction and its relationship to the Laramide orogeny, we compare the inverse convection model with plate reconstructions. Two prominent seismic anomalies on the Farallon plate recovered from inverse models coincide with paleogeographically-restored positions of conjugates to the Shatsky and Hess plateaus when they subducted beneath North America. The distributed shortening of the Laramide orogeny closely tracked the passage of the Shatsky conjugate beneath North America, while the effects of Hess conjugate subduction were restricted to the northern Mexico foreland belt. We find that Laramide uplifts were consequences of the removal, rather than the emplacement, of the Shatsky conjugate, and we predict that these subducted plateaus should be detectable by the USArray seismic experiment.
\r\n\r\nThe inverse convection models predict a continuous vertical motion history of western U.S., which is further validated by constraints on the vertical motion of the Colorado Plateau since the Cretaceous. With the arrival of the flat-lying Farallon slab, dynamic subsidence swept from west to east over the western U.S., peaking at 86 Ma within the Colorado Plateau. This eastward migrating dynamic subsidence is consistent with a recently compiled backstripping study that shows a long-wavelength residual subsidence shifting to the east, coincident with the passage of the flat slab beneath North America in our inverse model. Two stages of uplift followed the removal of the Farallon slab below the Colorado Plateau: one in the latest Cretaceous, and the other in the Eocene, with a cumulative uplift of ~1.2 km; the former represents the Laramide uplift which also marks the initial uplift of the entire western U.S. Both the descent of the slab and buoyant upwellings raised the Colorado Plateau to its current elevation during the Oligocene. A locally thick lithosphere enhances coupling to the upper mantle so that the Colorado Plateau has a higher topography with sharp edges. Our models also predict that the plateau tilted downward to the northeast before the Oligocene, caused by northeast-trending subduction of the Farallon slab, and that this northeast tilting diminished and reversed to the southwest during the Miocene in response to buoyant upwellings.
\r\n\r\nOverall, this thesis shows that the adjoint models with data assimilation are useful in linking surface evolution to deep mantle processes both over North America and areas beyond. While more research is clearly needed to construct a more earth-like model, this thesis presents an important advance in data-oriented geodynamic models.
", "doi": "10.7907/6VHZ-V130", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:3682", "collection": "thesis", "collection_id": "3682", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09212008-122525", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 5780898, "license": "other", "mime_type": "application/pdf", "url": "/3682/14/thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Computational Approaches to Localized Deformation Within the Lithosphere and for Crust-Mantle Interactions", "author": [ { "family_name": "Choi", "given_name": "Eun-seo", "clpid": "Choi-Eun-seo" } ], "thesis_advisor": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "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": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The thesis addresses selected problems related to localized deformation of the solid Earth\u2019s lithosphere that stem from non-uniform strengths or emerge from non-linear rheologies. A new code has been developed to model the spontaneous localization through strain-weakening plasticity. A code coupling technique is introduced as an attempt to efficiently solve multi-material and multi-physics problems like crust-mantle interactions.
\r\n\r\nWe first address a problem of localized deformation that is caused by pre-existing heterogeneities. Specifically, the effects of laterally varying viscous strength on the Cenozoic extension of the northern Basin and Range are investigated using numerical models. Three-dimensional viscous flow models with imposed plate motions and localized zones of low viscosity show that strain rates are concentrated in weak zones with adjacent blocks experiencing little deformation. This result can explain the geodetically discovered concentrated strain in the eastern part of the northern Basin and Range as the high strains are a response to far field plate motions within a locally less viscous mantle. The low viscosity of mantle is consistent with the low seismic velocities in the region.
\r\n\r\nAs an instance of spontaneously emergent localized deformations, brittle deformations in oceanic lithosphere are investigated next. We developed a Lagrangian finite difference code, SNAC, to investigate this class of problems. Brittle deformations are modeled as localized plastic strain. The detailed algorithm of SNAC is presented in Appendix A.
\r\n\r\nThe spacing of fracture zones in oceanic lithosphere is numerically explored. Numerical models represent a ridge-parallel cross-section of young oceanic lithosphere. An elasto-visco-plastic rheology can induce brittle deformation or creep according to the local temperature. The spacing of localized plastic zones, corresponding to fracture zones, decreases as crustal thickness increases. The stronger creep strength raises the threshold value of crustal thickness: If the crust is thinner than the threshold, the brittle deformation can evolve into primary cracks. Plastic flow rules are parametrized by the dilation angle. If the dilatational deformation is allowed in the plastic flow rules (dilation angle>0\u00b0), the primary cracks tend to be vertical; otherwise, a pair of primary cracks form a graben. The modeling results are compatible with the correlation between crustal thickness and the spacing of fracture zones found in different regions such as the Reykjanes ridge and the Australian Antarctic Discordance.
\r\n\r\nThree-dimensional (3D) numerical models are used to find the mechanics responsible for the various patterns made by the segments of the mid-ocean ridges and the structures connecting them. The models are initially loaded with thermal stresses due to the cooling of oceanic lithosphere and prescribed plate motions. The two driving forces are comparable in magnitude and the thermal stresses can exert ridge-parallel forces when selectively released by ridges and ridge-parallel structure. Represented by localized plastic strain, ridge segments interact in two different modes as they propagate towards each other: An overlapping mode where ridge segments overlap and bend toward each other and a connecting mode where two ridge segments are connected by a transform-like fault. As the ratio of thermal stress to spreading-induced stress (\u03b3) increases, the patterns of localized plastic strain change from the overlapping to connecting mode. Rate effects are taken into account by the spreading rate normalized by a reference-cooling rate (Pe\u2032) and the ratio of thermal stress to the reference spreading-induced stresses (\u03b3\u2032). The stability fields of the two modes are unambiguously defined by Pe\u2032 paired with \u03b3'.
\r\n\r\nCrust and mantle are distinct in terms of composition and rheology. To study the combined response of crust and mantle, it is necessary to solve multi-material and multi-physics problems that are numerically challenging. As an efficient way of solving such a problem, we introduce a code coupling technique. We adapt Pyre, a framework allowing distinct codes to exchange variables through shared interfaces, to the coupling of SNAC, a Lagrangian code for lithospheric dynamics, and CitcomS, an Eulerian code for mantle convection. The continuity of velocities and tractions and no-slip conditions are imposed on the interfaces. The benchmarks against analytic solutions to the bending of a thin plate verifies that SNAC gives an accurate solution for the given traction boundary condition. It is also shown that Pyre can correctly handle the data exchanges at the interfaces. In a preliminary high-resolution model, an elasto-visco-plastic lithosphere is coupled to a Newtonian viscous mantle. This coupled model shows a steady growth of dome in the lithosphere directly above a hot sphere placed in the mantle. However, the two coupled codes incur unnecessarily high numerical costs because they use different methods for time integration.
", "doi": "10.7907/81QV-Q705", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:1838", "collection": "thesis", "collection_id": "1838", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05162007-094830", "primary_object_url": { "basename": "1_Nadin_thesis_title.pdf", "content": "final", "filesize": 42257, "license": "other", "mime_type": "application/pdf", "url": "/1838/7/1_Nadin_thesis_title.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Structure and History of the Kern Canyon Fault System, Southern Sierra Nevada, California", "author": [ { "family_name": "Nadin", "given_name": "Elisabeth Sophia", "clpid": "Nadin-Elisabeth-Sophia" } ], "thesis_advisor": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" } ], "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.", "clpid": "Wernicke-B-P" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Results from field mapping and analyses of structural and petrochemical data from the southern Sierra Nevada batholith are presented to offer insight into the development of a major intra-arc fault system. The Kern Canyon fault system comprises an early ductile shear zone overprinted in its northern and central segments by a younger, recently active brittle fault. The divergence of these two faults at their middle latitudes poses a complex puzzle with regard to the physical and temporal evolution of deformation in the southern Sierra. Faulting began with ductile thrusting (the Proto-Kern Canyon fault zone) during emplacement of granitic plutons in the central to eastern part of the batholith at ca. 95 Ma. Early thrusting resulted in mismatched levels of pluton emplacement depths across the fault, truncation of significant regional geochemical markers in the batholith, and exhumation of the deepest level of the batholith in its southernmost region. Early ductile thrusting gave way to dextral strike-slip shearing by ca. 90 Ma. The youngest plutons in the batholith, emplaced along the fault between 90 and 80 Ma, are north-south elongate and reflect the dextral transpressional setting into which they were emplaced and deformed. Metamorphic country rocks were also highly sheared along the fault, and paleostress estimates from these deformed rocks suggest stresses along the middle segment of the Proto-Kern Canyon fault were 20\u201340 MPa, while strain rates were as high as 10-12 s-1 (comparable with other ductile faults). Strain studies and aspect ratios of igneous and metamorphic rocks strung out along the shear zone suggest ductile dextral displacement was 5\u201315 km. While ductile shearing ceased in the southern part of the batholith by ca. 85 Ma, it continued along the middle and northern segments of the Proto-Kern Canyon fault until ca. 80 Ma, when brittle deformation took over. This chronology suggests that the modern Kern Canyon fault, which shows ample evidence of activity into at least Quaternary time, initiated as a brittle structure in the southwestern part of the batholith, perhaps as early as 85 Ma, and shunted into the ductile shear zone at its middle latitudes ca. 5 Myrs later.", "doi": "10.7907/0WX9-S503", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:2060", "collection": "thesis", "collection_id": "2060", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05252006-191203", "primary_object_url": { "basename": "Smith-D-E-2006-thesis.pdf", "content": "final", "filesize": 121747741, "license": "other", "mime_type": "application/pdf", "url": "/2060/32/Smith-D-E-2006-thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A New Paradigm for Interpreting Stress Inversions from Focal Mechanisms: How 3D Stress Heterogeneity Biases the Inversions Toward the Stress Rate", "author": [ { "family_name": "Smith", "given_name": "Deborah Elaine", "orcid": "0000-0002-8317-7762", "clpid": "Smith-Deborah-Elaine" } ], "thesis_advisor": [ { "family_name": "Heaton", "given_name": "Thomas H.", "orcid": "0000-0003-3363-2197", "clpid": "Heaton-T-H" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Tromp", "given_name": "Jeroen", "orcid": "0000-0002-2742-8299", "clpid": "Tromp-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Heaton", "given_name": "Thomas H.", "orcid": "0000-0003-3363-2197", "clpid": "Heaton-T-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Current stress studies often utilize stress inversions of earthquake focal mechanisms to estimate four parameters of the spatially uniform stress tensor, three principal stress orientations, and a ratio of the principal stresses. An implicit assumption in these studies is that earthquakes are good random samplers of stress; hence, the set of earthquake focal mechanisms within some region can be used to estimate the spatial mean stress state within the region. Numerical simulations indicate some regions, such as Southern California, have sufficient stress heterogeneity to bias the stress inversions toward the stress rate orientation and that stress studies using stress inversions need to be reinterpreted by taking this bias into account. An outline of how to subtract out this bias to yield the actual spatial mean stress is presented.
\r\n\r\nNumerical simulations demonstrate that spatially heterogeneous stress in 3D can bias stress inversions of focal mechanisms toward the stress rate tensor instead of the stress. Stochastic models of 3D spatially heterogeneous stress are created, synthetic earthquake focal mechanisms are generated using the Hencky-Mises plastic yield criterion, and results are compared with Hardebeck's Southern California earthquake catalog [Hardebeck, 2006]. The presence of 3D spatial stress heterogeneity biases which orientations are most likely to fail, a bias toward the stress rate tensor. When synthetic focal mechanisms are compared to real data, estimates of two stress heterogeneity parameters for Southern California are obtained: 1) A spatial smoothing parameter, \u03b1\u22480.8, where \u03b1 describes the spectral falloff of 1D cross sections through a 3D grid for the three principal stresses and three orientation angles. 2) A heterogeneity ratio, HR \u2248 1.25, which describes the relative amplitude of the spatial stress heterogeneity to the spatial mean stress. The estimate for \u03b1 is tentative; however, varying \u03b1 for \u03b1 \u2264 1.0 has little to no effect on the observation that spatially heterogeneous stress biases failures toward the stress rate. The estimate for HR is more robust and produces a bias toward the stress rate of approximately 40%. If the spatial mean stress and the stress rate are not aligned, the average focal mechanism failure mechanism should yield a stress estimate from stress inversions, approximately halfway between the two.
", "doi": "10.7907/42NY-WV90", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:5137", "collection": "thesis", "collection_id": "5137", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12252005-151244", "primary_object_url": { "basename": "PhD_thesis_JBHS.pdf", "content": "final", "filesize": 57421208, "license": "other", "mime_type": "application/pdf", "url": "/5137/1/PhD_thesis_JBHS.pdf", "version": "v1.0.0" }, "type": "thesis", "title": "A Neotectonic Model of Taiwan, with a Focus on the Longitudinal Valley Suture", "author": [ { "family_name": "Shyu", "given_name": "J. Bruce Hao-Te Hsu", "orcid": "0000-0002-2564-3702", "clpid": "Shyu-J-Bruce-Hao-Te Hsu" } ], "thesis_advisor": [ { "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": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The disastrous effects of the 1999 Chi-Chi earthquake in Taiwan demonstrated an urgent need for better knowledge of the island's potential earthquake sources as well as their neotectonic context. Toward this end, we have utilized digital elevation models of the island to prepare a neotectonic map of Taiwan and proposed a neotectonic model for the orogen. Taiwan's numerous active faults and folds reveal that the active orogen is a tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the Eurasian continental margin. The collision and suturing in the southern part of the orogen and the post-collisional collapse and extension in the island's northern and northeastern flanks have produced eleven distinct neotectonic domains. Each domain is defined by a distinctive suite of active structures. In most of the domains, the size of the principal active fault is large enough to produce future earthquakes with magnitudes in the mid-7 range.
\r\n\r\nIn order to further understand the suturing processes, we have focused the second part of our investigation on the Longitudinal Valley suture in eastern Taiwan. The earthquakes of November 1951 within this suture constitute one of the most destructive seismic episodes in Taiwan's history. The surface ruptures of the earthquakes consist of three distinct sections, two of which are along segments of the Longitudinal Valley fault. From fluvial terraces along the Hsiukuluan River, we have reconstructed a shallow listric geometry for the Longitudinal Valley fault. On the other hand, many uplifted lateritic fluvial terraces along the eastern flank of the Central Range indicate the presence of a west-dipping Central Range reverse fault. We believe the majority of the horizontal shortening across the Longitudinal Valley suture is accommodated by the slip on the Longitudinal Valley fault. The remaining horizontal convergence may be absorbed by a combination of slip on the Central Range fault and subsidence of the Longitudinal Valley floor. The along-strike difference in geometry of the two major faults along the Longitudinal Valley is likely the manifestation of the northward maturation of the suturing of the Luzon volcanic arc to the Central Range continental sliver.
", "doi": "10.7907/X1XD-SB94", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:5137", "collection": "thesis", "collection_id": "5137", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12252005-151244", "primary_object_url": { "basename": "PhD_thesis_JBHS.pdf", "content": "final", "filesize": 57421208, "license": "other", "mime_type": "application/pdf", "url": "/5137/1/PhD_thesis_JBHS.pdf", "version": "v1.0.0" }, "type": "thesis", "title": "A Neotectonic Model of Taiwan, with a Focus on the Longitudinal Valley Suture", "author": [ { "family_name": "Shyu", "given_name": "J. Bruce Hao-Te Hsu", "orcid": "0000-0002-2564-3702", "clpid": "Shyu-J-Bruce-Hao-Te Hsu" } ], "thesis_advisor": [ { "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": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The disastrous effects of the 1999 Chi-Chi earthquake in Taiwan demonstrated an urgent need for better knowledge of the island's potential earthquake sources as well as their neotectonic context. Toward this end, we have utilized digital elevation models of the island to prepare a neotectonic map of Taiwan and proposed a neotectonic model for the orogen. Taiwan's numerous active faults and folds reveal that the active orogen is a tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the Eurasian continental margin. The collision and suturing in the southern part of the orogen and the post-collisional collapse and extension in the island's northern and northeastern flanks have produced eleven distinct neotectonic domains. Each domain is defined by a distinctive suite of active structures. In most of the domains, the size of the principal active fault is large enough to produce future earthquakes with magnitudes in the mid-7 range.
\r\n\r\nIn order to further understand the suturing processes, we have focused the second part of our investigation on the Longitudinal Valley suture in eastern Taiwan. The earthquakes of November 1951 within this suture constitute one of the most destructive seismic episodes in Taiwan's history. The surface ruptures of the earthquakes consist of three distinct sections, two of which are along segments of the Longitudinal Valley fault. From fluvial terraces along the Hsiukuluan River, we have reconstructed a shallow listric geometry for the Longitudinal Valley fault. On the other hand, many uplifted lateritic fluvial terraces along the eastern flank of the Central Range indicate the presence of a west-dipping Central Range reverse fault. We believe the majority of the horizontal shortening across the Longitudinal Valley suture is accommodated by the slip on the Longitudinal Valley fault. The remaining horizontal convergence may be absorbed by a combination of slip on the Central Range fault and subsidence of the Longitudinal Valley floor. The along-strike difference in geometry of the two major faults along the Longitudinal Valley is likely the manifestation of the northward maturation of the suturing of the Luzon volcanic arc to the Central Range continental sliver.
", "doi": "10.7907/X1XD-SB94", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:2115", "collection": "thesis", "collection_id": "2115", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05262006-172954", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 38371884, "license": "other", "mime_type": "application/pdf", "url": "/2115/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Spectral-Element Simulations of 3-D Seismic Wave Propagation and Applications to Source and Structural Inversions", "author": [ { "family_name": "Liu", "given_name": "Qinya", "orcid": "0000-0002-1071-2314", "clpid": "Liu-Qinya" } ], "thesis_advisor": [ { "family_name": "Tromp", "given_name": "Jeroen", "orcid": "0000-0002-2742-8299", "clpid": "Tromp-J" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Tromp", "given_name": "Jeroen", "orcid": "0000-0002-2742-8299", "clpid": "Tromp-J" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis presents a concise introduction to the spectral-element method and its applications to the simulation of seismic wave propagation in 3-D earth models. The spectral-element method is implemented in the regional scale for a 3-D integrated southern California velocity model. Significantly better waveform fits are achieved for the 3-D synthetics calculated compare to the 1-D synthetics generated from the 1-D standard southern California model, especially for many basin stations where strong amplifications are observed due to the very low wave-speed sediments. A hypothetical earthquake rupturing from northeast to southwest at the southern end of the San Andreas fault is simulated to improve our understanding of the seismic hazards in the Salton Trough region.
\r\n\r\nWith the improved 3-D Green's function, we perform source inversions for both the source mechanisms and event depths of $M_w geq 3.5$ earthquakes in southern California. The inversion results generally agree well with the results obtained by other traditional methods, but with significantly more stations used in the inversions. Time shifts are generally required to align the data and the synthetics, which provides a great dataset for the improvement of the 3-D velocity models in southern California.
\r\n\r\nWe use the adjoint method to formulate the tomographic inverse problem based upon a 3-D initial model. We calculate the sensitivity kernels, a key component of the tomographic inversion, that relate the perturbations of observations to the perturbations of the model parameters. These kernels are constructed by the interaction of the regular forward wavefield and the adjoint wavefield generated by putting the time-reversed signals at the receivers as simultaneous adjoint sources. We compute the travel-time sensitivity kernels for typical phases in both regional and global problems for educational purposes, and outline the procedures of applying the conjugate-gradient method to solve both source and structural inversion problems.
", "doi": "10.7907/JZ6J-0257", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:2366", "collection": "thesis", "collection_id": "2366", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06012006-174015", "primary_object_url": { "basename": "YTAN2006.pdf", "content": "final", "filesize": 16605275, "license": "other", "mime_type": "application/pdf", "url": "/2366/1/YTAN2006.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Broadband Waveform Modeling Over a Dense Seismic Network", "author": [ { "family_name": "Tan", "given_name": "Ying", "clpid": "Tan-Ying" } ], "thesis_advisor": [ { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Tromp", "given_name": "Jeroen", "orcid": "0000-0002-2742-8299", "clpid": "Tromp-J" }, { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "We developed a \"two-way\" calibration technique for studying clustered events, particularly their mechanisms and rupture directivities. First, we demonstrate that the magnitude 4 events with known source mechanisms can be used to calibrate the path effects on the short-period (0.5-2 sec) P waves, so that the corrected P waves can be modeled for determining focal mechanisms of the smaller events. The correction is formulated in terms of a station-specific \"Amplitude Amplification Factor\" (AAF), whose origin is mainly due to the site effect. Second, we show that the smaller events with radiation pattern corrections provide excellent empirical Green's functions (EGFs) for investigating the detailed rupture processes of the magnitude 4 events. In Chapter 2 of this thesis, we present the application of our methods to the 2003 Big Bear sequence.
\r\n\r\nA new technique CAPloc to retrieve full source parameters of small seismic events from regional seismograms is developed, which include origin time, epicenter location, depth, focal mechanism, and moment magnitude. In particular, we tested whether our new method could produce satisfactory results with as few as two stations, so that we can improve source estimates of poorly monitored events with sparse waveform data. We conducted the test in the Tibetan plateau. The focal mechanisms and locations determined from only two stations agree well with those from a well-distributed PASSCAL array.
\r\n\r\nWe use 49 Tonga-Fiji events recorded at the broadband TriNet array, southern California to develop a pure path upper-mantle shear velocity model. At the epicentral distances of 70-95 degree, multi-bounce S waves up to S5, including the guided waves, are observed and modeled to constrain the radial velocity structure. Our preferred model PAC06 contains a fast lid (Vsh=4.78 km/sec, Vsv=4.58 km/sec) ~60 km thick, and a prominent low velocity zone (LVZ) with the lowest velocities Vsh=4.34 km/sec, and Vsv=4.22 km/sec. Besides the 406 km and 651 km discontinuities, PAC06 also has a small (~1%) velocity jump at ~516 km. We consider these main features of PAC06 to be well determined, since PAC06 explains a large data set from various events. Therefore, it is ideally suited for comparing with mineralogical models.
", "doi": "10.7907/F4DB-2K48", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:99", "collection": "thesis", "collection_id": "99", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01102005-223039", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 47397009, "license": "other", "mime_type": "application/pdf", "url": "/99/1/Thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Cenozoic Plate Tectonic Reconstructions and Plate Boundary Processes in the Southwest Pacific", "author": [ { "family_name": "Keller", "given_name": "William R.", "clpid": "Keller-William-R" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Heaton", "given_name": "Thomas H.", "orcid": "0000-0003-3363-2197", "clpid": "Heaton-T-H" }, { "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": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The Australia-Pacific-Antarctic plate circuit has long been a weak link in global plate reconstruction models for Cenozoic time. The time period spanning chron 20 to chron 7 (43-25 Ma) is particularly problematic for global plate models because seafloor spreading was occurring in two poorly constrained regions in the Southwest Pacific - the Macquarie Basin southwest of New Zealand, and the Adare Basin north of the Ross Sea, Antarctica. I present a new shipboard dataset collected aboard several recent geophysical cruises which places important constraints on the tectonic evolution of these two regions. Utilizing multibeam bathymetry, magnetic, gravity, and seismic data in the Macquarie Basin, I am able to locate tectonic features and magnetic anomalies with greater accuracy than was previously possible. These tectonic features and magnetic anomalies are then used to calculate relative motion between the Australia and Pacific Plates for chrons 18-11 (40-30 Ma). I use revised locations of the rifted margins along the boundary of the Macquarie Basin to determine a best-fit pre-rift reconstruction for this region. During this same time period, seafloor spreading between East and West Antarctica was occurring along the Adare Trough, an extinct spreading center located north of the Ross Sea. Motion along the Adare Trough accounts for roughly 180 km of previously unrecognized motion between East and West Antarctica. I present multibeam and seismic data in the Adare Basin that place constraints on the timing and character of motion along this plate boundary.", "doi": "10.7907/VB6N-HC69", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2096", "collection": "thesis", "collection_id": "2096", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05262005-150027", "primary_object_url": { "basename": "JaneEDmochowskiThesis.pdf", "content": "final", "filesize": 5808741, "license": "other", "mime_type": "application/pdf", "url": "/2096/1/JaneEDmochowskiThesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Application of MODIS-ASTER (Master) Simulator Data to Geological Mapping of Young Volcanic Regions in Baja California, Mexico", "author": [ { "family_name": "Dmochowski", "given_name": "Jane Ellen", "orcid": "0000-0003-4491-2258", "clpid": "Dmochowski-Jane-Ellen" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "thesis_committee": [ { "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": "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Visible, near infrared, short-wave infrared, and thermal infrared multi-channel remote sensing data, MODIS-ASTER (MASTER), are used to extract geologic information from two volcanic regions in Baja California, Mexico: Tres Virgenes-La Reforma Volcanic Region and the volcanic island of Isla San Luis. The visible and near infrared and short-wave infrared data were atmospherically corrected and classified. The resulting classification roughly delineates surfaces that vary in their secondary minerals. Attempts to identify these minerals using ENVI's Spectral Analyst(TM) were moderately successful.
\r\n\r\nThe analysis of the thermal infrared data utilizes the shift to longer wavelengths in the Reststrahlen band as the mineralogy changes from felsic to mafic to translate the data into values of weight percent SiO2. The results indicate that the general approach tends to underestimate the weight percent SiO2 in the image. This discrepancy is removed with a \"site calibration,\" which provides good results in the calculated weight percent SiO2, with errors of a few percent. However, errors become larger with rugged topography or low solar angle at the time of image acquisition.
\r\n\r\nAnalysis of bathymetric data around Isla San Luis, and consideration of the island's alignment with the Ballenas transform fault zone to the south and volcanic seamounts nearby, suggest Isla San Luis is potentially volcanically active and could be the product of a \"leaky\" transform fault. The results from the image analysis in the Tres Virgenes-La Reforma Volcanic Region show the La Reforma and El Aguajito volcanic centers to be bimodal in composition and verify the most recent volcanism in the Tres Virgenes region to be basaltic-andesite. The results of fieldwork and image analysis indicate that the volcanic products of the central dome of La Reforma are likely a sequence of welded ash flow tuffs and lavas of varied composition, evidence of its origin as a caldera.
\r\n", "doi": "10.7907/DW9V-3831", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:4741", "collection": "thesis", "collection_id": "4741", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12032003-113513", "primary_object_url": { "basename": "ppersaud_thesis.pdf", "content": "final", "filesize": 67595371, "license": "other", "mime_type": "application/pdf", "url": "/4741/1/ppersaud_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Images of Early Continental Breakup in and around the Gulf of California and the Role of Basal Shear in Producing Wide Plate Boundaries", "author": [ { "family_name": "Persaud", "given_name": "Patricia", "orcid": "0000-0003-3462-7023", "clpid": "Persaud-Patricia" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Heaton", "given_name": "Thomas H.", "clpid": "Heaton-T-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Active faulting in the northern Gulf of California occurs over a broad zone, 70 x 200 km, affecting two-thirds of the width of new crust that has formed there starting at 6 Ma. This is an unusually wide plate boundary zone with a high density of faults and no evidence for the formation of normal oceanic crust. Over 3000 km of high-resolution, multichannel seismic data were used to map out this zone of distributed faulting and identify multiple basins within the broad rift zone. Previously, numerical models have shown that deformation shifts from one place to another by various mechanisms of strengthening of the active rift zone relative to adjacent regions. Models are presented here that for the first time, show the development of multiple active faults across the width of the plate boundary. These models do not rely on strengthening or weakening effects; rather they assume that shear at the base of the brittle crust is distributed and explore the effects of distributed shear on the style of deformation. Addiionally, the effect of obliquity on the style of deformation is studied and the styles of faulting produced in the models represent a wide range of geological structures, ranging from half-grabens to flower structures. The style of faulting in the northern Gulf of California is produced in a model with distributed shear using the published obliquity for this region.
\r\n\r\nOne mechanism for distributing shear at the base of the brittle crust is lower crustal flow. If a significant amount of lower continental crust exists within the Gulf, it may have flowed in the past. A study of the crustal thickness variations in the continental margins of the Gulf is presented here, that shows thinner crust in a ~50 km wide zone close to the Gulf, along the entire eastern Baja California peninsula. This thinned crust is associated with the eastern Peninsular Ranges batholith. In contrast, the western part of the batholith has a fairly uniform thickness of 35-40 km. It is possible that at the time of breakup, the lower crust was still behaving ductilely and that some of the lower continental crust from the margins now exists within the Gulf.
", "doi": "10.7907/8K9G-SS73", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:4741", "collection": "thesis", "collection_id": "4741", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12032003-113513", "primary_object_url": { "basename": "ppersaud_thesis.pdf", "content": "final", "filesize": 67595371, "license": "other", "mime_type": "application/pdf", "url": "/4741/1/ppersaud_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Images of Early Continental Breakup in and around the Gulf of California and the Role of Basal Shear in Producing Wide Plate Boundaries", "author": [ { "family_name": "Persaud", "given_name": "Patricia", "orcid": "0000-0003-3462-7023", "clpid": "Persaud-Patricia" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Heaton", "given_name": "Thomas H.", "clpid": "Heaton-T-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Active faulting in the northern Gulf of California occurs over a broad zone, 70 x 200 km, affecting two-thirds of the width of new crust that has formed there starting at 6 Ma. This is an unusually wide plate boundary zone with a high density of faults and no evidence for the formation of normal oceanic crust. Over 3000 km of high-resolution, multichannel seismic data were used to map out this zone of distributed faulting and identify multiple basins within the broad rift zone. Previously, numerical models have shown that deformation shifts from one place to another by various mechanisms of strengthening of the active rift zone relative to adjacent regions. Models are presented here that for the first time, show the development of multiple active faults across the width of the plate boundary. These models do not rely on strengthening or weakening effects; rather they assume that shear at the base of the brittle crust is distributed and explore the effects of distributed shear on the style of deformation. Addiionally, the effect of obliquity on the style of deformation is studied and the styles of faulting produced in the models represent a wide range of geological structures, ranging from half-grabens to flower structures. The style of faulting in the northern Gulf of California is produced in a model with distributed shear using the published obliquity for this region.
\r\n\r\nOne mechanism for distributing shear at the base of the brittle crust is lower crustal flow. If a significant amount of lower continental crust exists within the Gulf, it may have flowed in the past. A study of the crustal thickness variations in the continental margins of the Gulf is presented here, that shows thinner crust in a ~50 km wide zone close to the Gulf, along the entire eastern Baja California peninsula. This thinned crust is associated with the eastern Peninsular Ranges batholith. In contrast, the western part of the batholith has a fairly uniform thickness of 35-40 km. It is possible that at the time of breakup, the lower crust was still behaving ductilely and that some of the lower continental crust from the margins now exists within the Gulf.
", "doi": "10.7907/8K9G-SS73", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:6821", "collection": "thesis", "collection_id": "6821", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02152012-100334523", "primary_object_url": { "basename": "Nazareth_jj_2002.pdf", "content": "final", "filesize": 38384907, "license": "other", "mime_type": "application/pdf", "url": "/6821/1/Nazareth_jj_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "The Structure of the Crust and Distribution of Earthquakes in Southern California", "author": [ { "family_name": "Nazareth", "given_name": "Julie Jeannine", "clpid": "Nazareth-Julie-Jeannine" } ], "thesis_advisor": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Hauksson", "given_name": "Egill", "orcid": "0000-0002-6834-5051", "clpid": "Hauksson-E" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The lithologically and tectonically complex crust of southern California and the current broad deformation zone accommodating the relative motion between the Pacific and North American plates, result in significant variations in style, depth distribution, and rate of earthquakes, and thus also in the seismic hazard across southern California.\r\nAlthough the thickness of the seismogenic crust is an important parameter in seismic hazard analysis, it has never been determined systematically for southern California. Seismogenic thickness can be predicted by the depth distribution of the moment release of regional seismicity. The seismogenic thickness of southern California is highly variable, ranging from less than 10 km in the Salton Trough to greater than 25 km at the southwestern edge of the San Joaquin Valley. On average, the seismogenic thickness of southern California is 15.0 km. Seismogenic thickness along the major strike slip systems of southern California can vary significantly along strike. Fault segmentation based upon surface features does not correspond to the variation in seismogenic thickness and thus the potential down-dip width of the fault. A model of the broad scale features of the crust and upper mantle structure of the borderland-continent transition zone adjacent to Los Angeles constrains the crustal thickness and the location and width of the transition zone. The data require the Moho to deepen significantly to the north, dramatically increasing the crustal thickness over a relatively short distance of 20-25 km. The Moho is coherent and laterally continuous beneath the Inner California Borderland and transition zone. The Inner Borderland seems to be modified and thickened oceanic crust, with the oceanic upper mantle intact beneath it. The static stress change triggering model has some validity and can be useful in explaining apparently triggered seismicity within one fault length of a large mainshock. However, because its applicability varies between different sequences, its general application to seismic hazard evaluation requires more refinement and the inclusion of parameters such as tectonic regime, regional stress state, and fault strength.", "doi": "10.7907/6KNK-GG47", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:2566", "collection": "thesis", "collection_id": "2566", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06132002-094224", "primary_object_url": { "basename": "AnuThesis.pdf", "content": "final", "filesize": 5967910, "license": "other", "mime_type": "application/pdf", "url": "/2566/1/AnuThesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Investigating the Mechanics of Earthquakes Using Macroscopic Seismic Parameters", "author": [ { "family_name": "Venkataraman", "given_name": "Anupama", "clpid": "Venkataraman-Anupama" } ], "thesis_advisor": [ { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Heaton", "given_name": "Thomas H.", "orcid": "0000-0003-3363-2197", "clpid": "Heaton-T-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "To understand the physics of earthquake rupture mechanics, we have to relate seismologically observable parameters to the dynamics of faulting. One of the key seismological parameters that will help us achieve this objective is radiated energy. In this work, we develop a new method of estimating radiated energy from regional data using an empirical Green's functions; we also modify existing methods of estimating radiated energy from teleseismic data by improving the corrections applied to the observed seismic data for attenuation and directivity effects. \r\n\r\nWe compute teleseismic estimates of radiated energy for 23 large subduction zone earthquakes recorded between 1992 and 2001; most of these earthquakes have a magnitude, Mw > 7.5, but we also include some smaller (Mw~6.5) well-studied subduction zone earthquakes and 6 crustal earthquakes. We compile the static stress drop estimates for these 29 earthquakes from published literature. We then determine radiation efficiency of these earthquakes using a stress relaxation model that relates measurable and macroscopic seismological parameters to the physical processes on the fault zone via fracture energy. We also determine the rupture velocity of these earthquakes from published literature. A comparison of radiation efficiencies and rupture velocities of these earthquakes with the expected theoreticial values for different modes of crack propagation validates the use of the stress relaxation model to understand earthquake rupture mechanics.\r\n\r\nFrom our calculations, we observe that most earthquakes have radiation efficiencies between 0.25 and 1 and are hence efficient in generating seismic waves, but tsunami earthquakes and two deep earthquakes, the 1994 deep earthquake that occurred in Bolivia and the 1999 Russia-China border earthquake, have very small radiation efficiencies (<0.25) and hence dissipate a large amount of energy on the fault plane. We suggest that the difference in the radiation efficiencies of the different types of earthquakes could be due to fundamental differences in the rupture mechanics of different events. In case of deep events, the energy is probably dissipated in thermal processes on the fault zone, while it is possible that the morphology of the trench causes branching and bifurcation of rupture resulting in the large energy dissipation during the rupture process of tsunami earthquakes.", "doi": "10.7907/JS1E-X675", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:3477", "collection": "thesis", "collection_id": "3477", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09122001-155631", "primary_object_url": { "basename": "Niemi_2002_duplex.pdf", "content": "final", "filesize": 15008033, "license": "other", "mime_type": "application/pdf", "url": "/3477/1/Niemi_2002_duplex.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Extensional Tectonics in the Basin and Range Province and the Geology of the Grapevine Mountains, Death Valley Region, California and Nevada", "author": [ { "family_name": "Niemi", "given_name": "Nathan Alan", "orcid": "0000-0002-3380-3024", "clpid": "Niemi-Nathan-Alan" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "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": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Geologic mapping provides structural and stratigraphic observations which lead to new insights into the magnitude, timing, and rate of Cenozoic extensional tectonism in the Death Valley region of the Basin and Range province in the western United States. Detailed mapping of the Grapevine Mountains, in northeastern Death Valley, yields new information on the structural evolution of the Titus Canyon anticline, a west-vergent fold of the Cordilleran thrust belt. The Grapevine Mountains contain the longest exposure of west-vergent folding in the Death Valley region, and detailed mapping supports previous interpretation of this structure as a piece of a single, laterally continuous fold, whose extensionally dismembered fragments form a key marker in reconstructions of Basin and Range extension. Such an interpretation suggests >100 km of west-north-west translation of the Grapevine Mountains away from the Sheep Range in late Cenozoic time. Correlation and re-interpretation of Cenozoic sedimentary and volcanic strata between the Sheep Range and the Grapevine Mountains indicate that this extension occurred on two separate extensional systems, the Sheep Range detachment system, and the Northeastern Death Valley detachment system. The former was active from 16-14 Ma, while the latter was active from 12.5-8 Ma. In contrast, stratigraphic and sedimentological data from the Eagle Mountain Formation suggests that, although extension across the central Death Valley region accommodated a similar magnitude of extension as the northern Death Valley region, ~100 km, extension across this region occurred post-11 Ma, and largely between 8-6 Ma. New geodetic and paleoseismic data are also presented from the eastern Basin and Range. These data indicate that slow (~4 mm/yr), long term (100s ka) strain accumulation is accommodated, geologically, by short (1000s yr) periods of fast (>1cm/yr) strain release, suggesting that the appearance of diffuse deformation across the eastern Basin and Range is likely due to time-averaging of many temporally discrete high-strain release earthquake clusters. These observations together suggest that the diffuse nature of intra-continental extension in the Basin and Range province may be the result of the summation of many spatially and temporally distinct extensional events, which, when active, progress at very high rates", "doi": "10.7907/1HWM-JP59", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:4350", "collection": "thesis", "collection_id": "4350", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11012001-142941", "primary_object_url": { "basename": "01titlepage.pdf", "content": "final", "filesize": 30803, "license": "other", "mime_type": "application/pdf", "url": "/4350/1/01titlepage.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Seafloor Morphology of the Osbourn Trough and Kermadec Trench and II. Multiscale DynamiCS of Subduction Zones", "author": [ { "family_name": "Billen", "given_name": "Magali Isabelle", "orcid": "0000-0002-7316-1791", "clpid": "Billen-Magali-Isabelle" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Simons", "given_name": "Mark", "orcid": "0000-0003-1412-6395", "clpid": "Simons-M" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis aims to demonstrate that integration of detailed observations of deformation at short to long length scales with carefully formulated numerical modeling is an effective method for simulating the complex multiscale nature of mantle-lithosphere dynamics. In Part I, marine geophysical observations are used to determine the origin of the Osbourn Trough, a long linear depression within the Pacific Plate seaward of the Tonga-Kermadec Trench, and to determine the elastic strength of the subducting plate within the Kermadec Trench. Based on the morphology of the seafloor from swath bathymetry mapping and modeling of magnetic data, we conclude that the Osbourn Trough is an extinct spreading center which stopped spreading about 72 million years ago. Swath bathymetry mapping within the Kermadec Trench reveals extensive faulting within the trench on the subducting plate, with oblique grabens aligned perpendicular to the absolute plate motion direction. Using isostatic flexural response methods, we find that the flexural rigidity (1e19-1e20 Nm) is smaller than normally found for old oceanic lithosphere reflecting a local reduction in the strength of the plate.
\r\n\r\nIn Part II, regional 3-D dynamic models of the Tonga-Kermadec and Aleutian subduction zones are used to constrain lateral variations in viscosity in the upper mantle. Modeling of the dynamic topography of the overriding plate for the Tonga-Kermadec subduction zone requires a low viscosity and low density (-20 kg/m\u00b3) region within the wedge above the slab to decouple the slab-induced flow from. These efforts lead to a good fit to the observed shallow bathymetry on the overriding plate for a model with a slab density anomaly due to temperature of ~80 kg/m\u00b3. However, the geoid anomaly above the subduction zone is too large by 20-40 m at length scales of 100-1000 km. A reduction of the slab density by a factor of 1.5 is needed to match both the geoid and topography, suggesting the density anomaly of the slab due to temperature is compensated within the upper mantle (~100-300 km). Similar modeling for the Aleutians including a narrower low viscosity region and smaller density anomaly (-10 kg/m\u00b3) in the wedge is able to fit the geoid and topography without reducing the slab density.
", "doi": "10.7907/W46E-ZY34", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:4657", "collection": "thesis", "collection_id": "4657", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11252001-103911", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 20307207, "license": "other", "mime_type": "application/pdf", "url": "/4657/5/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Part I. Tectonic Evolution of the Northern Gulf of California, Mexico, Deduced from Conjugate Rifted Margins of the Upper Delf\u00edn Basin. Part II. Active Folding and Seismic Hazard in Central Los Angeles, California", "author": [ { "family_name": "Oskin", "given_name": "Michael Eugene", "orcid": "0000-0002-6631-5326", "clpid": "Oskin-Michael-Eugene" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "thesis_committee": [ { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "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": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Part I of this thesis addresses the tectonic evolution of the Pacific-North America plate boundary through northwest Mexico and its implications for rifting processes. Offset ignimbrites support 255\u00b110 km of opening across the Upper Delf\u00edn basin of the northern Gulf of California. Additional deformation from the continental margins supports 296\u00b117 km total plate boundary displacement between coastal Sonora and the Main Gulf Escarpment in Baja California, of which at least 276\u00b113 km occurred since ~6 Ma. This strain history requires that the plate boundary localized into the the northern Gulf of California during latest Miocene time. Only a narrow width of upper continental crust foundered into the Upper Delf\u00edn basin, such that most of the crust between Isla Tibur\u00f3n and Baja California must be new transitional oceanic crust and possibly lower continental crust contributed by inflow from the rift flanks. Extension of the margins of the Upper and Lower Delf\u00edn basins is <40% in most places, though the whole crustal column may have been thinned by a factor of two, further supporting that lower crustal flow has operated here. Opening of the Upper Delf\u00edn basin was accompanied by a steady or increased strain rate on its continental margins, contrary to the expected rheology of a narrow continental rift. Reevaluation of a critical deposit of marine rocks on Isla Tibur\u00f3n indicates that initial marine incursion in the northern Gulf of California also occurred during latest Miocene time. Together, these records suggest that opening of the Upper Delf\u00edn basin was an abrupt event, accompanied by a localized zone of intense extension, marine incursion, and a rapid increase in strain rate. Continental rupture in the Upper Delf\u00edn basin does not appear to have been a response to crustal weakening by intracontinental extension, but rather may have resulted from a significant increase in strain rate, brought on by a change in boundary forces. Part II of this thesis develops methods to estimate seismic hazard from blind reverse faults by analysis of fault-related folding of Late Quaternary strata, with application to the Elysian Park anticline of Los Angeles, California.
", "doi": "10.7907/4TQK-NH19", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:4657", "collection": "thesis", "collection_id": "4657", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11252001-103911", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 20307207, "license": "other", "mime_type": "application/pdf", "url": "/4657/5/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Part I. Tectonic Evolution of the Northern Gulf of California, Mexico, Deduced from Conjugate Rifted Margins of the Upper Delf\u00edn Basin. Part II. Active Folding and Seismic Hazard in Central Los Angeles, California", "author": [ { "family_name": "Oskin", "given_name": "Michael Eugene", "orcid": "0000-0002-6631-5326", "clpid": "Oskin-Michael-Eugene" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "thesis_committee": [ { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "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": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Part I of this thesis addresses the tectonic evolution of the Pacific-North America plate boundary through northwest Mexico and its implications for rifting processes. Offset ignimbrites support 255\u00b110 km of opening across the Upper Delf\u00edn basin of the northern Gulf of California. Additional deformation from the continental margins supports 296\u00b117 km total plate boundary displacement between coastal Sonora and the Main Gulf Escarpment in Baja California, of which at least 276\u00b113 km occurred since ~6 Ma. This strain history requires that the plate boundary localized into the the northern Gulf of California during latest Miocene time. Only a narrow width of upper continental crust foundered into the Upper Delf\u00edn basin, such that most of the crust between Isla Tibur\u00f3n and Baja California must be new transitional oceanic crust and possibly lower continental crust contributed by inflow from the rift flanks. Extension of the margins of the Upper and Lower Delf\u00edn basins is <40% in most places, though the whole crustal column may have been thinned by a factor of two, further supporting that lower crustal flow has operated here. Opening of the Upper Delf\u00edn basin was accompanied by a steady or increased strain rate on its continental margins, contrary to the expected rheology of a narrow continental rift. Reevaluation of a critical deposit of marine rocks on Isla Tibur\u00f3n indicates that initial marine incursion in the northern Gulf of California also occurred during latest Miocene time. Together, these records suggest that opening of the Upper Delf\u00edn basin was an abrupt event, accompanied by a localized zone of intense extension, marine incursion, and a rapid increase in strain rate. Continental rupture in the Upper Delf\u00edn basin does not appear to have been a response to crustal weakening by intracontinental extension, but rather may have resulted from a significant increase in strain rate, brought on by a change in boundary forces. Part II of this thesis develops methods to estimate seismic hazard from blind reverse faults by analysis of fault-related folding of Late Quaternary strata, with application to the Elysian Park anticline of Los Angeles, California.
", "doi": "10.7907/4TQK-NH19", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:7431", "collection": "thesis", "collection_id": "7431", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01242013-095637288", "primary_object_url": { "basename": "Hardebeck_jl_2001.pdf", "content": "final", "filesize": 30798697, "license": "other", "mime_type": "application/pdf", "url": "/7431/1/Hardebeck_jl_2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Crustal Stress Field in Southern California and its Implications for Fault Mechanics", "author": [ { "family_name": "Hardebeck", "given_name": "Jeanne Louise", "clpid": "Hardebeck-Jeanne-Louise" } ], "thesis_advisor": [ { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Hauksson", "given_name": "Egill", "orcid": "0000-0002-6834-5051", "clpid": "Hauksson-E" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Heaton", "given_name": "Thomas H.", "orcid": "0000-0003-3363-2197", "clpid": "Heaton-T-H" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "A high-resolution image of crustal stress orientation, determined from the inversion of earthquake focal mechanisms, provides insights into the mechanics and evolution of faulting in southern California. The plate boundary region is a wide, complex zone of deformation, and the stress field also appears to be spatially heterogeneous. Temporal variations in stress orientation are observed as well. The observed stress rotations due to the 1992 Landers earthquake are used to make an order of magnitude estimate of the deviatoric stress magnitude at seismogenic depths. The inferred deviatoric stress is on the order of 100 bar, an order of magnitude less than the fault strength predicted from laboratory experiments, implying that active faults in southern California are weak. The San Andreas Fault does not appear to be weaker than other faults, as it is well-oriented for failure in the stress field of its immediate surroundings. Earthquakes both modify and respond to the stress field. The 1992 Landers and 1994 Northridge earthquakes caused observable rotations of the stress axes, and the mainshock-induced static stress changes appear to have triggered some aftershocks. The number of aftershocks consistent with static stress triggering in each sequence is significantly greater than the number that would be expected to appear consistent by chance. Since small earthquakes are a response to the stress field, one might expect their stress drops to scale with effective normal stress. However, the stress drops of a set of small events do not appear to scale with depth, and therefore normal stress, in most of the seismogenic crust.", "doi": "10.7907/198c-1e38", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:3276", "collection": "thesis", "collection_id": "3276", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08302001-030958", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 2117873, "license": "other", "mime_type": "application/pdf", "url": "/3276/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "A Reciprocity Method for Multiple Source Simulations", "author": [ { "family_name": "Eisner", "given_name": "Leo", "clpid": "Eisner-Leo" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis develops and applies the reciprocity method to assess the seismic site and path effects at a chosen location of interest. To do this, we show that the reciprocity theorem is valid for this application, and develop a technique to represent velocity models of sedimentary basins. Using these tools we test the accuracy of synthetic seismograms computed for southern California. Finally, we apply the reciprocity technique to evaluate the site and path effects for three selected sites in southern California.
\r\n\r\nThe first chapter describes the reciprocity method for simulating seismograms due to multiple earthquake sources at a site of interest. It shows a theoretical proof of the method and discusses the practical implementation and accuracy for the finite difference technique. The numerical tests show that the reciprocal simulations can be performed with the same level of accuracy as the forward calculations.
\r\n\r\nThe second chapter develops a new methodology to represent models of sedimentary basins with extremely low near surface velocities by replacing these velocities with equivalent medium parameters for a finite frequency signal. The new model has a higher minimum velocity, which makes the numerical simulations feasible, and minimizes the difference between the seismograms from the original and new model.
\r\n\r\nThe third chapter validates the velocity model by comparing synthetics and data. It applies the reciprocity method and compares the full waveform synthetic seismograms with a large number of weak motion data. The discrepancies between the predicted waveforms and the data are interpreted by analyzing the attributes of seismograms to find regions of the model that are in error.
\r\n\r\nFinally the reciprocity technique is applied to calculate site and path effects in the Los Angeles area for three selected sites by simulating 75 source scenarios on 5 major southern California faults. The largest amplitudes at the selected sites are obtained from earthquakes on local faults rather than an earthquake on the San Andreas fault.
", "doi": "10.7907/Y9S0-0S33", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:15066", "collection": "thesis", "collection_id": "15066", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11282022-190922104", "type": "thesis", "title": "\u00b9\u2078O/\u00b9\u2076O Studies of Short-Lived (10-25 Year), Fumarolic (>500\u00b0C) Meteoric-Hydrothermal Events in the Outflow Sheets of Ash-Flow Tuffs", "author": [ { "family_name": "Holt", "given_name": "Elizabeth Warner", "clpid": "Holt-Elizabeth-Warner" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "thesis_committee": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "\u00b9\u2078O/\u00b9\u2076O data from the 0.76 Ma Bishop Tuff outflow sheet provide evidence\r\nfor a vigorous, short-Jived (\u224810-25 years), high-temperature (400\u00b0-650\u00b0C), fumarolic\r\nmeteoric-hydrothermal event immediately following eruption. This is proved by: (1) the\r\njuxtaposition in the upper, partially welded Bishop Tuff of low-\u00b9\u2078O groundmass/glass\r\n(\u03b4\u00b9\u2078O = -5 to +3) with coexisting quartz and feldspar phenocrysts having magmatic \u03b4\u00b9\u2078O values (+8.4 \u00b1 0.3; +7.2 \u00b1 0.3); and (2) the fact that these types of \u00b9\u2078O/\u00b9\u2076O signatures\r\ncorrelate very well with the morphological features and mapped zones of fumarolic activity.\r\nTen detailed \u03b4\u00b9\u2078O-depth profiles in various parts of the Bishop Tuff outflow sheet show\r\nevidence for two types of fumarolic meteoric-hydrothermal circulation systems in the upper\r\npart of the tuff; there is a broadly based, stratigraphically bound, 20- to 40-m-thick Upper\r\nLow-\u00b9\u2078O Zone (ULZ) that straddles the contact between the Tableland Unit and the Gorges\r\nUnit, and there is also a set of localized, 40- to 80-m-thick zones in the partially welded tuff\r\nin which extremely \u00b9\u2078O-depleted rock (\u03b4\u00b9\u2078O as low as -6.5) characterizes a Deep\r\nFumarolic System (DFS). This DFS is spatially associated with steep fissures, tubular\r\nconduits, and shallow-dipping columnar joints in cylindrical volumes of rock lying beneath\r\nmore than 1000 fumarolic mounds scattered across the surface of the tuff. Both of these\r\n\u00b9\u2078O-depleted zones are concentrated over areas where the underlying Densely Welded Zone\r\n(DWZ) is particularly thick, namely above pre-Bishop Tuff paleodrainages. The DWZ\r\nremained largely hot, ductile, and impermeable during fumarolic activity, which prevented\r\nthe heated meteoric fluids from penetrating the densely welded tuff until it cooled\r\nsufficiently so that throughgoing vertical fractures provided access to the base of the ash-flow\r\nsheet (at which time the fumarolic activity appears to have rapidly terminated).\r\nWhole-rock \u03b4\u00b9\u2078O values of samples collected from the surface of the 1912 ash-flow sheet\r\nat the Valley of Ten Thousand Smokes (VTTS), Alaska show analogous \u00b9\u2078O/\u00b9\u2076O\r\nsystematics and a similar range in \u03b4\u00b9\u2078O values (-0.1 to +12.6) to surface samples collected\r\nfrom the Bishop Tuff outflow sheet (+2.5 to +16.7).", "doi": "10.7907/8vdb-7r67", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:15066", "collection": "thesis", "collection_id": "15066", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11282022-190922104", "type": "thesis", "title": "\u00b9\u2078O/\u00b9\u2076O Studies of Short-Lived (10-25 Year), Fumarolic (>500\u00b0C) Meteoric-Hydrothermal Events in the Outflow Sheets of Ash-Flow Tuffs", "author": [ { "family_name": "Holt", "given_name": "Elizabeth Warner", "clpid": "Holt-Elizabeth-Warner" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "thesis_committee": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "\u00b9\u2078O/\u00b9\u2076O data from the 0.76 Ma Bishop Tuff outflow sheet provide evidence\r\nfor a vigorous, short-Jived (\u224810-25 years), high-temperature (400\u00b0-650\u00b0C), fumarolic\r\nmeteoric-hydrothermal event immediately following eruption. This is proved by: (1) the\r\njuxtaposition in the upper, partially welded Bishop Tuff of low-\u00b9\u2078O groundmass/glass\r\n(\u03b4\u00b9\u2078O = -5 to +3) with coexisting quartz and feldspar phenocrysts having magmatic \u03b4\u00b9\u2078O values (+8.4 \u00b1 0.3; +7.2 \u00b1 0.3); and (2) the fact that these types of \u00b9\u2078O/\u00b9\u2076O signatures\r\ncorrelate very well with the morphological features and mapped zones of fumarolic activity.\r\nTen detailed \u03b4\u00b9\u2078O-depth profiles in various parts of the Bishop Tuff outflow sheet show\r\nevidence for two types of fumarolic meteoric-hydrothermal circulation systems in the upper\r\npart of the tuff; there is a broadly based, stratigraphically bound, 20- to 40-m-thick Upper\r\nLow-\u00b9\u2078O Zone (ULZ) that straddles the contact between the Tableland Unit and the Gorges\r\nUnit, and there is also a set of localized, 40- to 80-m-thick zones in the partially welded tuff\r\nin which extremely \u00b9\u2078O-depleted rock (\u03b4\u00b9\u2078O as low as -6.5) characterizes a Deep\r\nFumarolic System (DFS). This DFS is spatially associated with steep fissures, tubular\r\nconduits, and shallow-dipping columnar joints in cylindrical volumes of rock lying beneath\r\nmore than 1000 fumarolic mounds scattered across the surface of the tuff. Both of these\r\n\u00b9\u2078O-depleted zones are concentrated over areas where the underlying Densely Welded Zone\r\n(DWZ) is particularly thick, namely above pre-Bishop Tuff paleodrainages. The DWZ\r\nremained largely hot, ductile, and impermeable during fumarolic activity, which prevented\r\nthe heated meteoric fluids from penetrating the densely welded tuff until it cooled\r\nsufficiently so that throughgoing vertical fractures provided access to the base of the ash-flow\r\nsheet (at which time the fumarolic activity appears to have rapidly terminated).\r\nWhole-rock \u03b4\u00b9\u2078O values of samples collected from the surface of the 1912 ash-flow sheet\r\nat the Valley of Ten Thousand Smokes (VTTS), Alaska show analogous \u00b9\u2078O/\u00b9\u2076O\r\nsystematics and a similar range in \u03b4\u00b9\u2078O values (-0.1 to +12.6) to surface samples collected\r\nfrom the Bishop Tuff outflow sheet (+2.5 to +16.7).", "doi": "10.7907/8vdb-7r67", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:16202", "collection": "thesis", "collection_id": "16202", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10062023-181634008", "primary_object_url": { "basename": "Holland_KG_1997.pdf", "content": "final", "filesize": 30615462, "license": "other", "mime_type": "application/pdf", "url": "/16202/1/Holland_KG_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Phase Changes and Transport Properties of Geophysical Materials Under Shock Loading", "author": [ { "family_name": "Holland", "given_name": "Kathleen Gabrielle", "clpid": "Holland-Kathleen-Gabrielle" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The lower mantle of the Earth is believed to be largely composed of (Mg, Fe)O (magnesiowiistite) and (Mg,Fe)SiO\u2083 (perovskite); thus the high pressure phase of (Mg,Fe)\u2082SiO\u2084 (olivine), which is believed to be perovskite plus magnesiowiistite is of geophysical interest. Radiative temperatures of single-crystal olivine starting material [(Mg_(0.9), Fe_(0.1))\u2082SiO\u2084] decreased abruptly from 7040 \u00b1 315 to 4300 \u00b1 270 K upon shock compression above 80 GPa. The data indicate that an upper bound to the solidus of the magnesiowiistite and perovskite assemblage at 4300 \u00b1 270 K is 130 \u00b1 3 GPa. These conditions correspond to those for partial melting at the base of the mantle, as has been suggested to occur within the recently discovered ultra-low-velocity zone (ULVZ) beneath the Central Pacific. We construct speculative high pressure phase diagrams for the MgO - SiO\u2082 system using experimental data from our work, and other mineral physics experiments.
\r\n\r\nIn separate experiments, time dependent shock temperatures were measured for stainless steel (SS) films sandwiched between two transparent Al\u2082O\u2083 anvils. The anvil material was the same as the driver material so that there would be symmetric heat flow from the sample. Inferred Hugoniot temperatures, T_h, of 5000 - 8500\u00b1500 Kat 222- 321 GPa are consistent with previous measurements in SS. Temperatures at the film\u00ad anvil interface (T_i), which are directly measured (rather than T_h) indicate that T_i did not decrease measurably during the approximately 250 ns that the shock wave took to traverse the Al\u2082O\u2083 anvil. Thus an upper bound is obtained for the thermal diffusivity of Al\u2082O\u2083 at the metal/anvil interface of K \u2264 14 \u00b1 5 cm\u00b2/s at 208 GPa and 2110 K. This is a factor of 1.6 lower than previously calculated values, resulting in a decrease of the inferred T_h by at least 400 K. The observed shock temperatures are combined with temperatures calculated from measured Hugoniots and are used to calculate the thermal conductivity of Al\u2082O\u2083. There was no measurable radiant-intensity decrease during the time when the shock wave propagated through the anvil; we infer from this that Al\u2082O\u2083 remained transparent while in the shocked state. Thus an Al\u2082O\u2083 anvil is sufficiently transparent for shock temperature measurements for metals, to at least 240 GPa.
\r\n\r\nFinally, shock temperature experiments employing a six-channel pyrometer were conducted on 200, 500, and 1000 \u00c5 thick films of Fe sandwiched between 3 mm thick anvils of Al\u2082O\u2083 and LiF, to measure the thermal diffusivity ratios of Al\u2082O\u2083/Fe and LiF/Fe, at high temperatures and pressures. Temperature decays of 3000 \u00b1 800 K in 250 ns were observed at Fe pressures of 194 - 303 GPa, which reflect the conduction of heat from the thin metal films into the anvil material. These results were achieved in experiments employing LiF anvils at 164 - 166 GPa and 4190 - 4220 K, and Al2O3 anvils at 196 - 303 GPa and 1410 - 2750 K. Thermal modeling of interface temperature versus time yields best fit thermal diffusivity ratios ranging from 15 \u00b1 30 to 80 \u00b1 20 (Fe/anvil) over the pressure and temperature range of the experiments. Calculated thermal conductivities for Fe, using electron gas theory, of 110 - 212 W /mK are used to calculate thermal conductivities for the anvil materials ranging from 6 to 12 W/mK. Debye theory predicts higher values of 8 to 34 W/mK. Data from previous experiments on thick (\u2265 100\u00b5m) films of Fe and stainless steel are combined with our present results from experiments on thin (\u2264 1000 \u00c5) films to infer a 5860 \u00b1 390 K Hugoniot temperature for the onset of melting of iron at 243 GPa. Our results address the question of whether radiation observed in shock temperature experiments on metals originates from the metal at the metal/ anvil interface or from the shocked anvil. We conclude that the photon flux from the shocked iron/anvil sandwich recorded in all experiments originates from the metal. Within the uncertainties of the shock temperature data, the uncertainties in shock temperatures resulting from the radiation from the anvils is negligible. This is in direct disagreement with previous conclusions of Kondo.
", "doi": "10.7907/cbd3-mk54", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:9923", "collection": "thesis", "collection_id": "9923", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09122016-121754817", "type": "thesis", "title": "I. Rupture Properties of Large Subduction Earthquakes. II. Broadband Upper Mantle Structure of Western North America", "author": [ { "family_name": "Melbourne", "given_name": "Timothy Ian", "clpid": "Melbourne-Timothy-Ian" } ], "thesis_advisor": [ { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "thesis_committee": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis contains two studies, one of which employs geodetic data bearing on large\r\nsubduction earthquakes to infer complexity of rupture duration, and the other is a\r\nhigh frequency seismological study of the upper mantle discontinuity structure under\r\nwestern North America and the East Pacific Rise. In the first part, we present\r\nGlobal Positioning System and tide gauge data which record the co-seismic deformation\r\nwhich accompanied the 1995 Mw8.0 Jalisco event offshore central Mexico, the\r\n1994 Mw7.5 Sanriku event offshore Northern Honshu, Japan, and the 1995 Mw8.1\r\nAntofagasta earthquake offshore Northern Chile. In two of the three cases we find\r\nthat the mainshocks were followed by significant amounts of rapid, post-seismic deformation\r\nwhich is best and most easily explained by continued slip near the co-seismic\r\nrupture patch. In Jalisco, we find that the post-seismic deformation which occurred\r\nduring the two weeks following the mainshock amounted to as much 70% of the co-seismic\r\ndeformation, from which we estimate an additional moment release of 40%,\r\nwhile in the Sanriku event an additional 30% moment release followed in the 10 days\r\nafter the mainshock. Because of the favorable geometry of the Jalisco network, we infer\r\nthat the post-seismic faulting occurred predominantly down-dip of the co-seismic\r\nrupture plane. This is the first documented case of rapid slip migration following\r\na large earthquake, and is pertinent to earthquake prediction based on precursory\r\ndeformation. Following the Antofagasta mainshock there was no rapid post-seismic\r\ndisplacement within the resolution of the GPS measurements, which equals roughly\r\n1% of the co-seismic displacement. As the three GPS data sets represent the best\r\nobservations of large subduction earthquakes to date and two of them show significant\r\namounts of aseismic energy release, they strongly suggest silent faulting may\r\nbe common in certain types of subduction zones. This, in turn, bears on estimates\r\nof global moment release, seismic coupling, and our understanding of the natural\r\nhazards associated with convergent margins.
\r\n\r\nThe second part of this dissertation utilizes high frequency body waves to infer\r\nthe upper mantle structure of western North America and the East Pacific Rise.\r\nAn uncharacteristically large Mw5.9 earthquake located in Western Texas provided a\r\nvivid topside reflection off the 410 Km velocity discontinuity (\"410\"), which we model\r\nto infer the fine details of this structure. We find that, contrary to conventional\r\nwisdom, the 410 is not sharp, and our results help reconcile seismic observations\r\nof 410 structure with laboratory predictions. By analyzing differences between our\r\nstructure and seismic 410 structure estimates under the nearby Gulf of California, we\r\nattempt to extract differences in temperature and mineralogy between subcontinental\r\nand suboceanic 410 structures.
\r\n\r\nExtending this analysis, we utilize teleseismic events from East Pacific Rise transform\r\nfaults to model multiple S upper mantle triplications. We find that for raypaths\r\ntraversing the rise crest the 1-D model TNA [Grand and Helmberger (1984)] derived\r\nfor the western US accurately predicts differential SnS-S travel times and triplication\r\nwaveform structure, implying that there is little velocity heterogeneity along the\r\nridge crest along nearly its entire length. We find that for energy traversing paths\r\nincreasingly away from the ridge axis there is no discernible change in the apparent\r\ndepth of the 410 and 670 Km discontinuities. In the shallowest mantle (uppermost 75\r\nKm), there is a strong lateral shear velocity gradient amounting to 3% over roughly\r\n150 Km. The LID, nonexistent at the ridge crest, grows slowly in thickness beyond\r\n150 Km from the axis. The compatible geodynamic model of these two results is that\r\nthe East Pacific Rise is not fed from the local lower mantle, rather, upper mantle\r\nmaterial must be transported laterally to supply the ridge axis spreading center, and\r\nthe LID reflects the source region of the East Pacific Rise magma supply.
", "doi": "10.7907/87nd-p040", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:9923", "collection": "thesis", "collection_id": "9923", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09122016-121754817", "type": "thesis", "title": "I. Rupture Properties of Large Subduction Earthquakes. II. Broadband Upper Mantle Structure of Western North America", "author": [ { "family_name": "Melbourne", "given_name": "Timothy Ian", "clpid": "Melbourne-Timothy-Ian" } ], "thesis_advisor": [ { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "thesis_committee": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis contains two studies, one of which employs geodetic data bearing on large\r\nsubduction earthquakes to infer complexity of rupture duration, and the other is a\r\nhigh frequency seismological study of the upper mantle discontinuity structure under\r\nwestern North America and the East Pacific Rise. In the first part, we present\r\nGlobal Positioning System and tide gauge data which record the co-seismic deformation\r\nwhich accompanied the 1995 Mw8.0 Jalisco event offshore central Mexico, the\r\n1994 Mw7.5 Sanriku event offshore Northern Honshu, Japan, and the 1995 Mw8.1\r\nAntofagasta earthquake offshore Northern Chile. In two of the three cases we find\r\nthat the mainshocks were followed by significant amounts of rapid, post-seismic deformation\r\nwhich is best and most easily explained by continued slip near the co-seismic\r\nrupture patch. In Jalisco, we find that the post-seismic deformation which occurred\r\nduring the two weeks following the mainshock amounted to as much 70% of the co-seismic\r\ndeformation, from which we estimate an additional moment release of 40%,\r\nwhile in the Sanriku event an additional 30% moment release followed in the 10 days\r\nafter the mainshock. Because of the favorable geometry of the Jalisco network, we infer\r\nthat the post-seismic faulting occurred predominantly down-dip of the co-seismic\r\nrupture plane. This is the first documented case of rapid slip migration following\r\na large earthquake, and is pertinent to earthquake prediction based on precursory\r\ndeformation. Following the Antofagasta mainshock there was no rapid post-seismic\r\ndisplacement within the resolution of the GPS measurements, which equals roughly\r\n1% of the co-seismic displacement. As the three GPS data sets represent the best\r\nobservations of large subduction earthquakes to date and two of them show significant\r\namounts of aseismic energy release, they strongly suggest silent faulting may\r\nbe common in certain types of subduction zones. This, in turn, bears on estimates\r\nof global moment release, seismic coupling, and our understanding of the natural\r\nhazards associated with convergent margins.
\r\n\r\nThe second part of this dissertation utilizes high frequency body waves to infer\r\nthe upper mantle structure of western North America and the East Pacific Rise.\r\nAn uncharacteristically large Mw5.9 earthquake located in Western Texas provided a\r\nvivid topside reflection off the 410 Km velocity discontinuity (\"410\"), which we model\r\nto infer the fine details of this structure. We find that, contrary to conventional\r\nwisdom, the 410 is not sharp, and our results help reconcile seismic observations\r\nof 410 structure with laboratory predictions. By analyzing differences between our\r\nstructure and seismic 410 structure estimates under the nearby Gulf of California, we\r\nattempt to extract differences in temperature and mineralogy between subcontinental\r\nand suboceanic 410 structures.
\r\n\r\nExtending this analysis, we utilize teleseismic events from East Pacific Rise transform\r\nfaults to model multiple S upper mantle triplications. We find that for raypaths\r\ntraversing the rise crest the 1-D model TNA [Grand and Helmberger (1984)] derived\r\nfor the western US accurately predicts differential SnS-S travel times and triplication\r\nwaveform structure, implying that there is little velocity heterogeneity along the\r\nridge crest along nearly its entire length. We find that for energy traversing paths\r\nincreasingly away from the ridge axis there is no discernible change in the apparent\r\ndepth of the 410 and 670 Km discontinuities. In the shallowest mantle (uppermost 75\r\nKm), there is a strong lateral shear velocity gradient amounting to 3% over roughly\r\n150 Km. The LID, nonexistent at the ridge crest, grows slowly in thickness beyond\r\n150 Km from the axis. The compatible geodynamic model of these two results is that\r\nthe East Pacific Rise is not fed from the local lower mantle, rather, upper mantle\r\nmaterial must be transported laterally to supply the ridge axis spreading center, and\r\nthe LID reflects the source region of the East Pacific Rise magma supply.
", "doi": "10.7907/87nd-p040", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:7626", "collection": "thesis", "collection_id": "7626", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04232013-084302487", "type": "thesis", "title": "I. Rigid Body Penetration into Brittle Material. II. Phase Change Effect on Shock Wave Propagation", "author": [ { "family_name": "Liu", "given_name": "Cangli", "clpid": "Liu-Cangli" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Ravichandran", "given_name": "Guruswami", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Ustundag", "given_name": "Ersan", "clpid": "Ustundag-E" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Part I.
\r\n\r\nWe have developed a technique for measuring the depth time history of rigid body penetration into brittle materials (hard rocks and concretes) under a deceleration of ~ 105 g. The technique includes bar-coded projectile, sabot-projectile separation,\r\ndetection and recording systems. Because the technique can give very dense data on penetration depth time history, penetration velocity can be deduced. Error analysis shows that the technique has a small intrinsic error of ~ 3-4 % in time during penetration, and 0.3 to 0.7 mm in penetration depth. A series of 4140 steel projectile penetration into G-mixture mortar targets have been conducted using the Caltech 40 mm gas/ powder gun in the velocity range of 100 to 500 m/s.
\r\n\r\nWe report, for the first time, the whole depth-time history of rigid body penetration into brittle materials (the G-mixture mortar) under 105 g deceleration. Based on the experimental results, including penetration depth time history, damage of recovered target and projectile materials and theoretical analysis, we find:
\r\n\r\n1. Target materials are damaged via compacting in the region in front of a projectile and via brittle radial and lateral crack propagation in the region surrounding the penetration path. The results suggest that expected cracks in front of penetrators may be stopped by a comminuted region that is induced by wave propagation. Aggregate erosion on the projectile lateral surface is < 20% of the final penetration depth. This result suggests that the effect of lateral friction on the penetration process can be ignored.
\r\n\r\n2. Final penetration depth, Pmax, is linearly scaled with initial projectile energy per unit cross-section area, es , when targets are intact after impact. Based on the experimental data on the mortar targets, the relation is Pmax(mm) 1.15es (J/mm2 ) + 16.39.
\r\n\r\n3. Estimation of the energy needed to create an unit penetration volume suggests that the average pressure acting on the target material during penetration is ~ 10 to 20 times higher than the unconfined strength of target materials under quasi-static loading, and 3 to 4 times higher than the possible highest pressure due to friction and material strength and its rate dependence. In addition, the\r\nexperimental data show that the interaction between cracks and the target free surface significantly affects the penetration process.
\r\n\r\n4. Based on the fact that the penetration duration, tmax, increases slowly with es and does not depend on projectile radius approximately, the dependence of tmax on projectile length is suggested to be described by tmax(\u03bcs) = 2.08es (J/mm2 + 349.0 x m/(\u03c0R2), in which m is the projectile mass in grams and R is the projectile radius in mm. The prediction from this relation is in reasonable agreement with the experimental data for different projectile lengths.
\r\n\r\n5. Deduced penetration velocity time histories suggest that whole penetration history is divided into three stages: (1) An initial stage in which the projectile velocity change is small due to very small contact area between the projectile and target materials; (2) A steady penetration stage in which projectile velocity continues to decrease smoothly; (3) A penetration stop stage in which projectile deceleration jumps up when velocities are close to a critical value of ~ 35 m/s.
\r\n\r\n6. Deduced averaged deceleration, a, in the steady penetration stage for projectiles with same dimensions is found to be a(g) = 192.4v + 1.89 x 104, where v is initial projectile velocity in m/s. The average pressure acting on target materials during penetration is estimated to be very comparable to shock wave pressure.
\r\n\r\n7. A similarity of penetration process is found to be described by a relation between normalized penetration depth, P/Pmax, and normalized penetration time, t/tmax, as P/Pmax = f(t/tmax, where f is a function of t/tmax. After f(t/tmax is determined using experimental data for projectiles with 150 mm length, the penetration depth time history for projectiles with 100 mm length predicted by this relation is in good agreement with experimental data. This similarity also predicts that average deceleration increases with decreasing projectile length, that is verified by the experimental data.
\r\n\r\n8. Based on the penetration process analysis and the present data, a first principle model for rigid body penetration is suggested. The model incorporates the models for contact area between projectile and target materials, friction coefficient, penetration stop criterion, and normal stress on the projectile surface. The most important assumptions used in the model are: (1) The penetration process can be treated as a series of impact events, therefore, pressure normal to projectile surface is estimated using the Hugoniot relation of target material; (2) The necessary condition for penetration is that the pressure acting on target materials is not lower than the Hugoniot elastic limit; (3) The friction force on projectile lateral surface can be ignored due to cavitation during penetration. All the parameters involved in the model are determined based on independent experimental data. The penetration depth time histories predicted from the model are in good agreement with the experimental data.
\r\n\r\n9. Based on planar impact and previous quasi-static experimental data, the strain rate dependence of the mortar compressive strength is described by \u03c3f/\u03c30f = exp(0.0905(log(\u03ad/\u03ad_0) 1.14, in the strain rate range of 10-7/s to 103/s (\u03c30f and \u03ad are reference compressive strength and strain rate, respectively). The non-dispersive\r\nHugoniot elastic wave in the G-mixture has an amplitude of ~ 0.14 GPa and a velocity of ~ 4.3 km/s.
\r\n\r\nPart II.
\r\n\r\nStress wave profiles in vitreous GeO2 were measured using piezoresistance gauges in the pressure range of 5 to 18 GPa under planar plate and spherical projectile impact. Experimental data show that the response of vitreous GeO2 to planar shock loading\r\ncan be divided into three stages: (1) A ramp elastic precursor has peak amplitude of 4 GPa and peak particle velocity of 333 m/s. Wave velocity decreases from initial longitudinal elastic wave velocity of 3.5 km/s to 2.9 km/s at 4 GPa; (2) A ramp wave with amplitude of 2.11 GPa follows the precursor when peak loading pressure is 8.4 GPa. Wave velocity drops to the value below bulk wave velocity in this stage; (3) A shock wave achieving final shock state forms when peak pressure is > 6 GPa. The Hugoniot relation is D = 0.917 + 1.711u (km/s) using present data and the data of Jackson and Ahrens [1979] when shock wave pressure is between 6 and 40 GPa for \u03c10 = 3.655 gj cm3 . Based on the present data, the phase change from 4-fold to 6-fold coordination of Ge+4 with O-2 in vitreous GeO2 occurs in the pressure range of 4 to 15 \u00b1 1 GPa under planar shock loading. Comparison of the shock loading data for\r\nfused SiO2 to that on vitreous GeO2 demonstrates that transformation to the rutile structure in both media are similar. The Hugoniots of vitreous GeO2 and fused SiO2 are found to coincide approximately if pressure in fused SiO2 is scaled by the ratio of fused SiO2to vitreous GeO2 density. This result, as well as the same structure, provides the basis for considering vitreous Ge02 as an analogous material to fused SiO2 under shock loading. Experimental results from the spherical projectile impact demonstrate: (1) The supported elastic shock in fused SiO2 decays less rapidly than a linear elastic wave when elastic wave stress amplitude is higher than 4 GPa. The supported elastic shock in vitreous GeO2 decays faster than a linear elastic wave; (2) In vitreous GeO2 , unsupported shock waves decays with peak pressure in the phase transition range (4-15 GPa) with propagation distance, x, as \u03b1 1/x-3.35 , close to the prediction of Chen et al. [1998]. Based on a simple analysis on spherical wave propagation, we find that the different decay rates of a spherical elastic wave in fused SiO2 and vitreous GeO2 is predictable on the base of the compressibility variation with stress under one-dimensional strain condition in the two materials.
\r\n\r\n", "doi": "10.7907/w8gc-n615", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:5932", "collection": "thesis", "collection_id": "5932", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072010-160325894", "primary_object_url": { "basename": "Zajac_bj_1998.pdf", "content": "final", "filesize": 13435545, "license": "other", "mime_type": "application/pdf", "url": "/5932/1/Zajac_bj_1998.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "The State of Stress as Inferred from Deviated Boreholes: Constraints on the Tectonics of Offshore Central California and Cook Inlet, Alaska", "author": [ { "family_name": "Zajac", "given_name": "Blair J.", "clpid": "Zajac-Blair-J" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "thesis_committee": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis introduces a new method of constraining the vector directions of the three principal stresses and their relative magnitudes, by using borehole breakouts in non-vertical drill holes. Unlike older stress state measurements from breakouts, this work does not presume that one of the principal stresses is Vertical. This method has important uses in complicated three-dimensional structures, such as in the Los Angeles basin, and in oil drilling applications.
\r\n\r\nChapter 1 discusses why knowledge of the three-dimensional stress tensor is relevant to today's science and examines the applications of the stress state determination technique discussed herein. The history of previous work is also described.
\r\n\r\nIn Chapter 2 I discuss the techniques of determining the stress tensor from borehole breakouts, examining the physics of borehole breakouts, the theory of the inversion technique used, and data processing issues. The theory and data processing issues are not discussed separately in this work, since data processing issues often prompted new theoretical techniques. I first examine the physics of borehole breakouts and how the orientation of breakouts on the borehole wall relates to the local stress field. A new borehole breakout selection scheme which takes into account highly non-vertical boreholes is then presented along with a discussion of the real world problems of data gathering, identification, and processing. Having selected a borehole breakout data set using the criteria, I invert for the best fitting stress state using a new technique combining genetic algorithms and non- differential function optimizers. Finally, I present a way in which 95% confidence limits can be placed on the resulting stress tensor.
\r\n\r\nWith all of the technical and theoretical pieces in place, I now examine several different data sets. Chapter 3 examines a borehole breakout data set publish by Qian and Pedersen [1991] from the Siljan Deep Drilling Project in Sweden and demonstrates that even for simple borehole breakout data sets, the stress state inversions assuming a vertical principal stress direction may fall outside of the 95% confidence limits of an inversion allowing non-vertical principal stress directions. My technique of displaying the borehole breakout data makes the data quality more obvious as compared to the way Qian and Pedersen [1991] plotted the data.
\r\n\r\nChapter 4 examines a borehole breakout data set from the offshore Santa Maria Basin, California. This analysis presents vertical borehole breakout data that represent a maximum horizontal principal stress direction of N7\u00b0E, roughly consistent with other earthquake focal mechanism, GPS, and borehole breakout studies in the area. However, the stress state inversion of breakouts identified in the vertical and a limited number of nearly horizontal boreholes suggests a stress state very different from any other stress state results. This could imply that the three dimensional stress in the Santa Maria Basin is very complicated. However, given the limited amount of borehole breakouts identified in nearly horizontal wells, the stress state results from this data set are inconclusive.
\r\n\r\nChapter 5 examines the largest data set used in this study, from a series of oil wells in Cook Inlet, Alaska. These are borehole caliper arm data from 21 different wells reaching a maximum deviation of 54\u00b0 and 3,223 m true vertical depth. Stress state inversions of 31 different subsets of the borehole breakout data were performed. Inversion of breakouts identified in the top two of three marker beds analyzed in wells drilled from the Baker platform identified nearly degenerate thrust faulting stress states with the maximum principal stress axis, S_1, oriented horizontally WNWESE, perpendicular to the NNE-trending anticlinal structures. The stress state from the deepest marker is also a nearly degenerate thrust faulting stress state with S_1 oriented NNW\u2014SSE, aligned with the regional direction of relative plate motion between the North American and Pacific plates. In between the shallow and deep stress state is an apparent normal faulting stress state with S_2 oriented subhorizontally ENE\u2014WSW. This clockwise rotation of the stress tensor as a function of depth suggests that the stress field changes with depth, from a shallow stress state responsible for the local NNE-trending structures to a deeper one from the North American and Pacific plates' collision zone. The observed normal faulting stress state between the two thrust faulting stress states is anomalous and may represent some sort of transition from the shallow to the deep stress state. Stress state profiles in 500 m true vertical depth (TVD) intervals show consistently oriented thrust faulting stress regimes with NNW\u2014SSE trending S_1 azimuths. The thrust faulting S_3 principal stress direction is consistently within 30\u00b0 of vertical, suggesting that while the assumption of a purely vertical principal stress direction is not valid, the stress tensor does not significantly rotate away from the surface conditions that require a purely vertical stress tensor. The nearly degenerate thrust faulting stress states determined from the Granite Point and the 10.8 km distant Baker platform breakouts are nearly identical, implying that the technique of using deviated borehole breakouts to invert for the regional stress is valid. The orientations of the maximum horizontal stress determined from the Cook Inlet borehole breakouts are consistent with other stress indicators in south-central Alaska and consistent with the direction of relative plate motion between the North American Plate and the Pacific plate. The S_1 axis for the Cook Inlet field trends due south plunging 3\u00b0. The 95% confidence limits allow the S_1 azimuth to vary from N156\u00b0E to N195\u00b0E and the plunge to vary from 10\u00b0 to -4\u00b0. This stress state does not appear representative of the stress field for each subset of breakouts. The Granite Point S1 axis trends N19\u00b0W plunging 3\u00b0; the 95% confidence limits allow the azimuth to vary from N42\u00b0W to N7\u00b0E and the plunge to vary from 1\u00b0 to 6\u00b0. The Baker platform S_1 axis trends N170\u00b0E plunging 8\u00b0; the 95% confidence limits on S_1 allow its azimuth to vary from N139\u00b0E to N191\u00b0E and its plunge to vary from 1\u00b0 to 15\u00b0. Finally, the Dillon platform S_1 axis trends N69\u00b0W plunging 2\u00b0; the 95% confidence limits constrain the S_1 azimuth from N268\u00b0E to N324\u00b0E and the plunge from 8\u00b0 to -4\u00b0. The more westerly orientation of S_1 at the Dillon platform may be related to the local NNE-trending anticlinal structures in the Cook Inlet Basin.
\r\n\r\nChapter 6 concludes and summarized the results and conclusions from the thesis.
\r\n\r\nThe first appendix contains in minute detail some of the mathematics describing the boreholes, breakouts, and coordinate system rotations used to perform this work. The second appendix contains the individual discussion and plots of the raw dipmeter data from all of the Cook Inlet, Alaska wells.
", "doi": "10.7907/S3V0-3M43", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:1342", "collection": "thesis", "collection_id": "1342", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04112005-132058", "primary_object_url": { "basename": "Zachariasen_j_1998.pdf", "content": "final", "filesize": 29852895, "license": "other", "mime_type": "application/pdf", "url": "/1342/1/Zachariasen_j_1998.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Paleoseismology and Paleogeodesy of the Sumatran Subduction Zone: A Study of Vertical Deformation Using Coral Microatolls", "author": [ { "family_name": "Zachariasen", "given_name": "Judith Ann", "clpid": "Zachariasen-Judith-Ann" } ], "thesis_advisor": [ { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "thesis_committee": [ { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Corals from Western Sumatra retain stratigraphic records of relative sea-level change that can be used to infer vertical displacement rates in the hanging wall block of the Sumatran subduction zone. The upward growth of the coral \"microatolls\" is limited by low water levels, and fluctuations in water level produce measurable changes in the coral morphology. Furthermore, the corals contain annual growth rings, which act as an internal chronometer of coral growth history. The microatolls, which are widespread and can live for decades or centuries, can serve as natural long-term tide gauges, recording sea-level variations over wide intervals of space and time.
\r\n\r\nRelative sea-level records from living corals from the outer-arc islands and mainland coast constrain the nature of recent vertical deformation over the subduction zone. Emerged fossil corals from the islands, dated with U-Th geochronometry, constrain the paleoseismic and paleogeodetic history of the region.
\r\n\r\nStratigraphic analysis of cross-sectional slabs cut from living coral heads reveals that the islands have been submerging at rates of 4-10 mm/yr over the last four or five decades, while the mainland has remained relatively stable. Many fossil corals died in the early 1800's. Their age and morphological signature indicate they died as a result of coseismic uplift of more than lm during the last great subduction-zone earthquake in this region, in 1833, following decades of interseismic submergence at rates similar to modern rates.
\r\n\r\nOther sampled corals died at earlier times throughout the late to mid-Holocene. Their presence in the intertidal zone suggests that little permanent vertical deformation has occurred here over the past several thousand years, and, therefore, most of the accumulated interseismic strain is recovered during earthquakes. The temporal distribution of coral deaths suggests an average earthquake recurrence interval for subduction zone events of about 230 years. Combining sea-level histories from modern, 1833, and older corals yields partial records of co- and interseismic vertical displacement for multiple earthquake cycles. Such displacement records from the hanging wall of a major plate boundary can help constrain models of subduction-zone deformation.
", "doi": "10.7907/YYWJ-R395", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:11380", "collection": "thesis", "collection_id": "11380", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02012019-101059213", "primary_object_url": { "basename": "Brady_RJ_1998.pdf", "content": "final", "filesize": 60445928, "license": "other", "mime_type": "application/pdf", "url": "/11380/1/Brady_RJ_1998.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "The Geology of the Gold Butte Breakaway Zone and the Mechanical Evolution of Normal Fault Systems", "author": [ { "family_name": "Brady", "given_name": "Robert John", "clpid": "Brady-Robert-John" } ], "thesis_advisor": [ { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-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": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "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": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The Gold Butte breakaway zone is the easternmost and oldest of the major Tertiary normal fault systems in the central Basin and Range province of the southwestern U.S. The normal faults of the breakaway zone crop out across the South Virgin Mountains (SVM), and define a narrow boundary zone between the Colorado Plateau and the highly extended central Basin and Range Province. Geochronologic data, including 40Ar/39Ar muscovite ages, (U-Th)/He apatite ages, and (U-Th)/Pb monazite ages, suggest that extension within the breakaway zone occurred rapidly at ~15 Ma, consistent with earlier work (Fitzgerald, 1991). Approximately 400 km2 of the SVM was mapped at a scale of 1:12 000. This mapping shows that extension initiated on a set of steeply west dipping normal faults. Later faults soled into the earlier faults rather than cutting them, requiring motion to continue on both fault sets, with the earlier faults remaining active to dips of less than 30\u00b0. Total extension across the SVM is at least ~21 km. The latest deformation to affect the region was isostatic uplift of the footwall to the Lakeside Mine Fault Zone, with resultant formation of a basement dome and associated folding and late stage faulting adjacent to the dome. Seismic reflection data suggest that the crustal thickness of the region is 30 to 35 kilometers. When combined with the high average elevation of the denuded basement block, this suggests that extension of the upper crust has been compensated by emplacement of fluid mid to lower crust. The lower crust and Moho are seismically transparent, so the lower crust is probably not made up of basaltic intrusions; rather, it has probably flowed in from surrounding areas. A mechanical model has been developed which considers the behavior of an elastic upper crust isostatically compensated by flow in the lower crust. This model shows that gradual isostatic upwarping of the thinning region should generate compressional flexural stresses near the base of the elastic upper crust. These stresses may shut down the active faults and force new normal faults to root outside of the extended region.
", "doi": "10.7907/715q-hm18", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:11380", "collection": "thesis", "collection_id": "11380", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02012019-101059213", "primary_object_url": { "basename": "Brady_RJ_1998.pdf", "content": "final", "filesize": 60445928, "license": "other", "mime_type": "application/pdf", "url": "/11380/1/Brady_RJ_1998.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "The Geology of the Gold Butte Breakaway Zone and the Mechanical Evolution of Normal Fault Systems", "author": [ { "family_name": "Brady", "given_name": "Robert John", "clpid": "Brady-Robert-John" } ], "thesis_advisor": [ { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-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": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "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": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The Gold Butte breakaway zone is the easternmost and oldest of the major Tertiary normal fault systems in the central Basin and Range province of the southwestern U.S. The normal faults of the breakaway zone crop out across the South Virgin Mountains (SVM), and define a narrow boundary zone between the Colorado Plateau and the highly extended central Basin and Range Province. Geochronologic data, including 40Ar/39Ar muscovite ages, (U-Th)/He apatite ages, and (U-Th)/Pb monazite ages, suggest that extension within the breakaway zone occurred rapidly at ~15 Ma, consistent with earlier work (Fitzgerald, 1991). Approximately 400 km2 of the SVM was mapped at a scale of 1:12 000. This mapping shows that extension initiated on a set of steeply west dipping normal faults. Later faults soled into the earlier faults rather than cutting them, requiring motion to continue on both fault sets, with the earlier faults remaining active to dips of less than 30\u00b0. Total extension across the SVM is at least ~21 km. The latest deformation to affect the region was isostatic uplift of the footwall to the Lakeside Mine Fault Zone, with resultant formation of a basement dome and associated folding and late stage faulting adjacent to the dome. Seismic reflection data suggest that the crustal thickness of the region is 30 to 35 kilometers. When combined with the high average elevation of the denuded basement block, this suggests that extension of the upper crust has been compensated by emplacement of fluid mid to lower crust. The lower crust and Moho are seismically transparent, so the lower crust is probably not made up of basaltic intrusions; rather, it has probably flowed in from surrounding areas. A mechanical model has been developed which considers the behavior of an elastic upper crust isostatically compensated by flow in the lower crust. This model shows that gradual isostatic upwarping of the thinning region should generate compressional flexural stresses near the base of the elastic upper crust. These stresses may shut down the active faults and force new normal faults to root outside of the extended region.
", "doi": "10.7907/715q-hm18", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:5932", "collection": "thesis", "collection_id": "5932", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072010-160325894", "primary_object_url": { "basename": "Zajac_bj_1998.pdf", "content": "final", "filesize": 13435545, "license": "other", "mime_type": "application/pdf", "url": "/5932/1/Zajac_bj_1998.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "The State of Stress as Inferred from Deviated Boreholes: Constraints on the Tectonics of Offshore Central California and Cook Inlet, Alaska", "author": [ { "family_name": "Zajac", "given_name": "Blair J.", "clpid": "Zajac-Blair-J" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "thesis_committee": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis introduces a new method of constraining the vector directions of the three principal stresses and their relative magnitudes, by using borehole breakouts in non-vertical drill holes. Unlike older stress state measurements from breakouts, this work does not presume that one of the principal stresses is Vertical. This method has important uses in complicated three-dimensional structures, such as in the Los Angeles basin, and in oil drilling applications.
\r\n\r\nChapter 1 discusses why knowledge of the three-dimensional stress tensor is relevant to today's science and examines the applications of the stress state determination technique discussed herein. The history of previous work is also described.
\r\n\r\nIn Chapter 2 I discuss the techniques of determining the stress tensor from borehole breakouts, examining the physics of borehole breakouts, the theory of the inversion technique used, and data processing issues. The theory and data processing issues are not discussed separately in this work, since data processing issues often prompted new theoretical techniques. I first examine the physics of borehole breakouts and how the orientation of breakouts on the borehole wall relates to the local stress field. A new borehole breakout selection scheme which takes into account highly non-vertical boreholes is then presented along with a discussion of the real world problems of data gathering, identification, and processing. Having selected a borehole breakout data set using the criteria, I invert for the best fitting stress state using a new technique combining genetic algorithms and non- differential function optimizers. Finally, I present a way in which 95% confidence limits can be placed on the resulting stress tensor.
\r\n\r\nWith all of the technical and theoretical pieces in place, I now examine several different data sets. Chapter 3 examines a borehole breakout data set publish by Qian and Pedersen [1991] from the Siljan Deep Drilling Project in Sweden and demonstrates that even for simple borehole breakout data sets, the stress state inversions assuming a vertical principal stress direction may fall outside of the 95% confidence limits of an inversion allowing non-vertical principal stress directions. My technique of displaying the borehole breakout data makes the data quality more obvious as compared to the way Qian and Pedersen [1991] plotted the data.
\r\n\r\nChapter 4 examines a borehole breakout data set from the offshore Santa Maria Basin, California. This analysis presents vertical borehole breakout data that represent a maximum horizontal principal stress direction of N7\u00b0E, roughly consistent with other earthquake focal mechanism, GPS, and borehole breakout studies in the area. However, the stress state inversion of breakouts identified in the vertical and a limited number of nearly horizontal boreholes suggests a stress state very different from any other stress state results. This could imply that the three dimensional stress in the Santa Maria Basin is very complicated. However, given the limited amount of borehole breakouts identified in nearly horizontal wells, the stress state results from this data set are inconclusive.
\r\n\r\nChapter 5 examines the largest data set used in this study, from a series of oil wells in Cook Inlet, Alaska. These are borehole caliper arm data from 21 different wells reaching a maximum deviation of 54\u00b0 and 3,223 m true vertical depth. Stress state inversions of 31 different subsets of the borehole breakout data were performed. Inversion of breakouts identified in the top two of three marker beds analyzed in wells drilled from the Baker platform identified nearly degenerate thrust faulting stress states with the maximum principal stress axis, S_1, oriented horizontally WNWESE, perpendicular to the NNE-trending anticlinal structures. The stress state from the deepest marker is also a nearly degenerate thrust faulting stress state with S_1 oriented NNW\u2014SSE, aligned with the regional direction of relative plate motion between the North American and Pacific plates. In between the shallow and deep stress state is an apparent normal faulting stress state with S_2 oriented subhorizontally ENE\u2014WSW. This clockwise rotation of the stress tensor as a function of depth suggests that the stress field changes with depth, from a shallow stress state responsible for the local NNE-trending structures to a deeper one from the North American and Pacific plates' collision zone. The observed normal faulting stress state between the two thrust faulting stress states is anomalous and may represent some sort of transition from the shallow to the deep stress state. Stress state profiles in 500 m true vertical depth (TVD) intervals show consistently oriented thrust faulting stress regimes with NNW\u2014SSE trending S_1 azimuths. The thrust faulting S_3 principal stress direction is consistently within 30\u00b0 of vertical, suggesting that while the assumption of a purely vertical principal stress direction is not valid, the stress tensor does not significantly rotate away from the surface conditions that require a purely vertical stress tensor. The nearly degenerate thrust faulting stress states determined from the Granite Point and the 10.8 km distant Baker platform breakouts are nearly identical, implying that the technique of using deviated borehole breakouts to invert for the regional stress is valid. The orientations of the maximum horizontal stress determined from the Cook Inlet borehole breakouts are consistent with other stress indicators in south-central Alaska and consistent with the direction of relative plate motion between the North American Plate and the Pacific plate. The S_1 axis for the Cook Inlet field trends due south plunging 3\u00b0. The 95% confidence limits allow the S_1 azimuth to vary from N156\u00b0E to N195\u00b0E and the plunge to vary from 10\u00b0 to -4\u00b0. This stress state does not appear representative of the stress field for each subset of breakouts. The Granite Point S1 axis trends N19\u00b0W plunging 3\u00b0; the 95% confidence limits allow the azimuth to vary from N42\u00b0W to N7\u00b0E and the plunge to vary from 1\u00b0 to 6\u00b0. The Baker platform S_1 axis trends N170\u00b0E plunging 8\u00b0; the 95% confidence limits on S_1 allow its azimuth to vary from N139\u00b0E to N191\u00b0E and its plunge to vary from 1\u00b0 to 15\u00b0. Finally, the Dillon platform S_1 axis trends N69\u00b0W plunging 2\u00b0; the 95% confidence limits constrain the S_1 azimuth from N268\u00b0E to N324\u00b0E and the plunge from 8\u00b0 to -4\u00b0. The more westerly orientation of S_1 at the Dillon platform may be related to the local NNE-trending anticlinal structures in the Cook Inlet Basin.
\r\n\r\nChapter 6 concludes and summarized the results and conclusions from the thesis.
\r\n\r\nThe first appendix contains in minute detail some of the mathematics describing the boreholes, breakouts, and coordinate system rotations used to perform this work. The second appendix contains the individual discussion and plots of the raw dipmeter data from all of the Cook Inlet, Alaska wells.
", "doi": "10.7907/S3V0-3M43", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:7272", "collection": "thesis", "collection_id": "7272", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11152012-083234968", "type": "thesis", "title": "I. Neoproterozoic-Paleozoic Supercontinental Tectonics and True Polar Wander. II. Temporal and Spatial Distributions of Proterozoic Glaciations", "author": [ { "family_name": "Evans", "given_name": "David Aspinwall Dai", "orcid": "0000-0001-8952-5273", "clpid": "Evans-David-Aspinwall-Dai" } ], "thesis_advisor": [ { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The Proterozoic Eon, occupying nearly half of Earth history from 2.5 to 0.5 billion\r\nyears ago, is marked at its beginning and end by dramatic events in the tectonic,\r\npaleoclimatic, chemical, and biological evolution of the planet. The onset of the\r\nProterozoic Eon witnessed the emergence of continents and perhaps the introduction of\r\nplate tectonics, Earth's first extensive ice ages, oxygenation of the hydro-atmosphere, and\r\ndevelopment of eukaryotes. The end of the Proterozoic Eon is characterized by\r\nsupercontinental turnover and very rapid continental drift rates, a series of glaciations\r\nwhich left their marks on every continent, the rise of atmospheric oxygen to sustain\r\nmulticelled organisms, and an evolutionary \"explosion\" of animal life.
\r\n\r\nEstablishment of coherent paleogeographies of these important intervals is a crucial\r\nprerequisite for describing the events and understanding the underlying processes.\r\nPaleomagnetism is the most direct quantitative method for charting continental drift through\r\ntime. The purpose of this dissertation is to use paleomagnetism to constrain tectonic and\r\npaleoclimatic processes at the beginning and end of the Proterozoic Eon.
\r\n\r\nA paleomagnetic study of Early Cambrian rocks in western Mongolia finds somewhat\r\nambiguous results and addresses tectonic models of the Paleo-Asian Ocean. Review of the\r\nmost reliable studies among the Proterozoic-Cambrian global paleomagnetic database\r\npermits the hypothesis that an episode of inertial interchange true polar wander (TPW)\r\noccurred in Early Cambrian time. The Cambrian TPW event and a previously hypothesized\r\nOrdovician-Devonian TPW migration share a common axis and suggest the existence of\r\nlong-lived mantle mass anomalies inherited from the previous supercontinent, Rodinia.\r\nThe breakup of Rodinia and subsequent amalgamation of Gondwanaland appear analogous\r\nin several ways to the Gondwanaland-Super-Asia supercontinental transition, suggesting a\r\n500-600-Myr cyclicity.
\r\n\r\nAn exhaustive review of paleomagnetic and geochronological constraints upon\r\nNeoproterozoic glaciogenic deposits fails to find a convincing high-paleolatitude\r\noccurrence. Detailed study of one of these deposits in South China reveals a reliable\r\npaleomagnetic pole implying a paleolatitude of 34\u00b12\u00b0, with both paleoclimatic and\r\npaleogeographic implications. A reliable estimation of 11\u00b15\u00b0 depositional paleolatitude for\r\n2.2-billion-year-old lavas directly overlying a glaciogenic formation in South Africa,\r\nextends the occurrence of low-latitude continental ice sheets further back into the\r\nPrecambrian.
\r\n\r\n", "doi": "10.7907/grbc-aa41", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:5516", "collection": "thesis", "collection_id": "5516", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01132010-093747416", "primary_object_url": { "basename": "Nagy_ea_1997.pdf", "content": "final", "filesize": 17758433, "license": "other", "mime_type": "application/pdf", "url": "/5516/1/Nagy_ea_1997.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Extensional Deformation and Volcanism Within the Northern Puertecitos Volcanic Province, Sierra Santa Isabel, Baja California, Mexico", "author": [ { "family_name": "Nagy", "given_name": "Elizabeth Ann", "clpid": "Nagy-Elizabeth-Ann" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Geologic features at the western edge of the Gulf Extensional Province (GEP) in northeastern Baja California, Mexico, record details of Pacific-North American (PAC-NAM) plate boundary history prior to and during its establishment within the Gulf of California. Methods of study in Santa Isabel Wash (SIW) (informally named) in the northern Sierra Santa Isabel include geologic mapping of ~140 km^2 (1:20000 scale) along the northern margin of the Miocene-Pliocene Puertecitos Volcanic Province (PVP), ^(40)Ar/^(39)Ar geochronology, electron microprobe analysis, paleomagnetic study, and petrography. Local Neogene stratigraphy (spanning ~17-6 Ma) includes volcaniclastic breccias, basaltic to dacitic lava flows, and rhyolitic pyroclastic flow deposits. The completeness of the lithologic package improves stratigraphic correlations between the PVP and nearby regions.
\r\n\r\nHigh-angle extension-related faults cut all rocks in SIW. The southeastward projection of the pre-6 Ma Matorni accommodation zone, which separates a northern region of greater and more prolonged extension from a less extended southern zone, may pass on the north side of SIW. Paleomagnetic analysis indicates no vertical axis rotations in SIW since 6 Ma. This contrasts with regions north of the Matomi accommodation zone where clockwise rotation has accompanied extensional deformation since 3-6 Ma. About 500 meters of post-6 Ma, E-side-down displacement occurs across two major, NNW-striking normal faults on the west side of SIW. These, and smaller synthetic and antithetic faults in the hanging walls, accommodate up to 4% E- to ENE-directed extension. Quaternary deformation is also documented.
\r\n\r\nA new model developed to explain ENE-directed extension in northeastern Baja California partitions present-day PAC-NAM plate motion between NNW-striking, sinistral dip-slip faults and N- to NNW-striking, dextral (oblique?) strike-slip fault(s) in the northernmost Gulf of California. The model offers explanations for the geometry of plate motion accommodation between the latitudes of the Agua Blanca fault and the PVP, bathymetric features near Wagner and Consag basins, the position and jumps of nearby spreading centers since 6 Ma, the greater width and bend in coastline of the northernmost Gulf of California, the incorporation of the PVP into the GEP 2-3 Ma, and suggests a transitional tectonic scenario between oceanic spreading centers and continental transforms (\"Wagner Transition Zone\").
", "doi": "10.7907/znpy-3311", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:16178", "collection": "thesis", "collection_id": "16178", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09072023-170005385", "primary_object_url": { "basename": "Holt_JW_1997.pdf", "content": "final", "filesize": 65389008, "license": "other", "mime_type": "application/pdf", "url": "/16178/1/Holt_JW_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Detailed Records of Geomagnetic Field Behavior from Death Valley and Hawaii. II. An Age Constraint on Gulf of California Rifting from Santa Rosal\u00eda, Baja California", "author": [ { "family_name": "Holt", "given_name": "John William", "clpid": "Holt-John-William" } ], "thesis_advisor": [ { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" } ], "thesis_committee": [ { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Detailed records of geomagnetic field behavior were produced and analyzed from Plio/Pleistocene sedimentary rocks of Death Valley, California and from Pleistocene/Holocene volcanic rocks of Hawaii. These records provide new information about geomagnetic field polarity reversals, excursions, secular varia\u00adtion, and the paleomagnetic recording process in sediments. In addition, a magnetostratigraphic and geochronlogic study of Mio/Pliocene marine sedimen\u00adtary rocks in Baja California, Mexico was performed in order to provide a new age constraint on Gulf of California rifting.
\r\n\r\nThe paleomagnetic studies in Death Valley were undertaken on siltstones, sand\u00ad stones, and evaporites exposed along the southern Death Valley fault zone in the Confidence Hills. These rocks contain multiple records of the R\u00e9union and Olduvai normal-polarity subchrons (2.15 - 2.13 Ma and 1.95 - 1.79 Ma, respec\u00adtively) within rocks formed as a result of deposition in different subenvironments of a saline ephemeral lake, with an average deposition rate of ~ 30 cm/kyr. Variations in bedding attitudes between the exposed sections allow a fold test of paleomagnetic directions. Two records of the upper Olduvai polarity reversal were obtained which agree despite differences of lithology, depositional environ\u00adment, and structural tilting. These records indicate several phases of polarity shifts during the transition of the geomagnetic field from normal to reversed polarity. Transitional virtual geomagnetic poles (VGP's) lie in longitudinal bands ~ 90\u00b0 away from the sampling site longitude, vastly different from VGP's pro\u00adduced by studies in other locations around the world but consistent with site\u00ad dependent trends of VGP paths observed in global data compilations. Studies of the anisotropy of anhysteritic remanence conclude that inclination shallowing in sediments during periods of low ambient magnetic field intensity is a possible cause for this site dependence of VGP paths. However, some aspect of the transitional geomagnetic field is recorded by the sedimentary rocks of Death Valley whether or not inclination shallowing took place.
\r\n\r\nA detailed record of the R\u00e9union normal-polarity subchron was obtained from one of the sections in the Confidence Hills. This record shows that the R\u00e9union subchron was a single normal-polarity event of ~ 20 kyr duration, which is a significant finding due to the lack of previous data in this time interval. The pres\u00adence of a lithofacies which contains disruptive anhydrite crystals dispersed throughout the matrix creates two small gaps in the record just prior to the nor\u00admal-polarity R\u00e9union interval. Remagnetizations within this lithofacies facilitate the interpretation of the depositional environment responsible for growth of the disruptive evaporites.
\r\n\r\nSamples of the 1 km core produced by the Hawaii Scientific Drilling Project (HSDP) provided the basis for a study of geomagnetic field excursions and secular variation during the past 400 kyr at Hawaii. This core consists of over 200 lava flows erupted from Mauna Loa and Mauna Kea volcanoes. In contrast to previous hypotheses that the non-dipole field has been anomalously low in the central Pacific region for the past few hundred kyrs, the results of this study show that secular variation, and hence, the non-dipole field component, at Hawaii is consistent with secular variation elsewhere on the globe for the past 400 kyr. In addition, the data show evidence for a persistent axial quadrupole in the time\u00ad averaged field. This research also resulted in the first records of geomagnetic field excursions in the central Pacific which may be correlated with those found elsewhere on the globe, lending support to the hypothesis that these are global events rather than local perturbations of the geomagnetic field.
\r\n\r\nPaleomagnetic and geochronologic studies of marine sedimentary rocks in the Santa Rosal\u00eda basin, Baja California Sur, show that despite the presence of local copper ore deposition, primary magnetic remanence directions may be obtained from most of the marine sandstones overlying the basement in that area. Using preliminary magnetostratigraphy and an \u2074\u2070Ar/\u00b3\u2079Ar isotopic age of 6.76 \u00b1 0.45 Ma (1\u03c3) obtained for a volcanic unit interbedded with the sandstones, a correla\u00adtion with the geomagnetic polarity time scale was made possible, yielding an age of 7.1 \u00b1 0.05 Ma for the base of the marine section. This provides a new age constraint on Gulf of California rifting and may help to refine models of North America - Pacific plate boundary interactions during the period 12 - 3.5 Ma.
", "doi": "10.7907/y9sj-ca84", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:5516", "collection": "thesis", "collection_id": "5516", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01132010-093747416", "primary_object_url": { "basename": "Nagy_ea_1997.pdf", "content": "final", "filesize": 17758433, "license": "other", "mime_type": "application/pdf", "url": "/5516/1/Nagy_ea_1997.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Extensional Deformation and Volcanism Within the Northern Puertecitos Volcanic Province, Sierra Santa Isabel, Baja California, Mexico", "author": [ { "family_name": "Nagy", "given_name": "Elizabeth Ann", "clpid": "Nagy-Elizabeth-Ann" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Geologic features at the western edge of the Gulf Extensional Province (GEP) in northeastern Baja California, Mexico, record details of Pacific-North American (PAC-NAM) plate boundary history prior to and during its establishment within the Gulf of California. Methods of study in Santa Isabel Wash (SIW) (informally named) in the northern Sierra Santa Isabel include geologic mapping of ~140 km^2 (1:20000 scale) along the northern margin of the Miocene-Pliocene Puertecitos Volcanic Province (PVP), ^(40)Ar/^(39)Ar geochronology, electron microprobe analysis, paleomagnetic study, and petrography. Local Neogene stratigraphy (spanning ~17-6 Ma) includes volcaniclastic breccias, basaltic to dacitic lava flows, and rhyolitic pyroclastic flow deposits. The completeness of the lithologic package improves stratigraphic correlations between the PVP and nearby regions.
\r\n\r\nHigh-angle extension-related faults cut all rocks in SIW. The southeastward projection of the pre-6 Ma Matorni accommodation zone, which separates a northern region of greater and more prolonged extension from a less extended southern zone, may pass on the north side of SIW. Paleomagnetic analysis indicates no vertical axis rotations in SIW since 6 Ma. This contrasts with regions north of the Matomi accommodation zone where clockwise rotation has accompanied extensional deformation since 3-6 Ma. About 500 meters of post-6 Ma, E-side-down displacement occurs across two major, NNW-striking normal faults on the west side of SIW. These, and smaller synthetic and antithetic faults in the hanging walls, accommodate up to 4% E- to ENE-directed extension. Quaternary deformation is also documented.
\r\n\r\nA new model developed to explain ENE-directed extension in northeastern Baja California partitions present-day PAC-NAM plate motion between NNW-striking, sinistral dip-slip faults and N- to NNW-striking, dextral (oblique?) strike-slip fault(s) in the northernmost Gulf of California. The model offers explanations for the geometry of plate motion accommodation between the latitudes of the Agua Blanca fault and the PVP, bathymetric features near Wagner and Consag basins, the position and jumps of nearby spreading centers since 6 Ma, the greater width and bend in coastline of the northernmost Gulf of California, the incorporation of the PVP into the GEP 2-3 Ma, and suggests a transitional tectonic scenario between oceanic spreading centers and continental transforms (\"Wagner Transition Zone\").
", "doi": "10.7907/znpy-3311", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:4372", "collection": "thesis", "collection_id": "4372", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11022007-093001", "type": "thesis", "title": "Seismic Strain Rates and the State of Tectonic Stress in the Southern California Region", "author": [ { "family_name": "Huang", "given_name": "Weishi", "clpid": "Huang-Weishi" } ], "thesis_advisor": [ { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" } ], "thesis_committee": [ { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Allen", "given_name": "Clarence R.", "clpid": "Allen-C-R" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "I determine 505 fault plane solutions from the first motions of P-waves for the\r\nbackground seismicity (3.0≤ M≤6.0, 1981-1991) and collect mechanisms of major\r\nearthquakes (M≥6.0, 1927-1994) from the literature in the southern California region.\r\nThen I study the seismic strain and tectonic stress fields in individual domains (ten in\r\ntotal) by analyzing these mechanism data. The seismic strain tensors are obtained by\r\ntensorial summation of individual seismic moment tensors. The tectonic stress tensors\r\nare determined by performing numerical inversions of the slip vector data, using\r\nAngelier's (1990) method. The findings are summarized as follows:
\r\n\r\n(1) Of the 505 fault plane solutions for the 1981-1991 background seismicity, 54%\r\nare strike-slip (SF), 21 % reverse (RF), 17% normal (NF), and 8% oblique-slip\r\nfaulting (OS) events. The catalog of the major earthquakes for the period 1927-\r\n1994 also displays similar proportions of the faulting mechanisms;
\r\n\r\n(2) The similarity of the focal mechanisms can be measured by a parameter, seismic\r\nconsistency (Sc) introduced by Apperson (1991). It is defined as the ratio of the\r\nscalar moment of the total moment tensor to the sum of the scalar moments of\r\nindividual moment tensors. In southern California, the Brawley fault (BYF)\r\ndomain shows the highest Sc (0.70), whereas the White Wolf fault (WWF)\r\ndomain displays the lowest Sc (0.44). Sc values in other domains vary between\r\nthe above two values;
\r\n\r\n(3) The depths of possible low-angle faults inferred from the fault plane solutions\r\nvary from 20 km in the Transverse ranges where N-S convergence dominates, to\r\nonly 1 km in the southern Sierra Nevada fault (SSNF) domain where E-W divergence\r\ndominates. Our current data do not show the existence of a sigle unified\r\nseismically-active master detachment in the seismogenic zone;
\r\n\r\n(4) The axes of the maximum principal stress, \u03b41. are oriented N6\u00b0E \u00b111\u00b0, whereas\r\nthose of the maximum principal strain, \u03b51 are oriented N5\u00b0E \u00b121\u00b0;
\r\n\r\n(5) The strain and stress tensors are similar to each other in the Mojave (MVE), San\r\nJacinto (SJF), Elsinore (ESF), BYF, western and eastern Transverse Ranges\r\n(WTR, ETR) domains, but dissimilar in the central Transverse Ranges (CTR),\r\nNewport-Inglewood fault (NIF), WWF, and SSNF domains. Areas with small\r\nvalues of \u03a6 = (\u03b42 - \u03b43)/(\u03b41 - \u03b43) (<0.35) such as the WTR, CTR, and NIF domains are associated with more than 40% of RF events. Areas with \u03a6 values around 0.5\r\nsuch as the SJF, ETR, WWF, ESF, BYF, and MVE domains are associated with\r\nmore than 47% of SF events. The SSNF domain has a large \u03a6 (>0.65) and\r\nshows 49% of NF events, Variation of the state of stress appears to be in the\r\nTransverse Ranges where hypocenters are generally deep. Other areas show a\r\nrelatively stable state of stress throughout the seismogenic depth;
\r\n\r\n(6) Seismic fraction of deformation, \u03b7, is a measure of the deformation mode. It is\r\ndefined as the ratio of seismic strain rate to the total deformation rate. Because of\r\nthe limited seismic data, we can usually estimate the apparent instead of the real\r\nseismic fraction of deformation. Therefore, caution must be exercised in applying\r\nthe values of \u03b7 to evaluations of seismic potential, In southern California, there\r\nare some indications that areas in which seismic deformation nearly accounts for\r\nthe total deformation are typically associated with cold and rigid batholithic rocks\r\nor high seismic velocity anomalies such as in the SJF, south central MVE, WWF,\r\nand possibly the ETR domains. However, areas with low seismic velocity\r\nanomalies are not free of earthquakes as seen, for example, in the BYF domain,\r\nwhich shows \u03b7 = 0.6-1.0. Other domains show \u03b7 < 0.4. The problem of whether the\r\nmissing deformation is being released aseismically or has accumulated elastically\r\nremains to be resolved.
", "doi": "10.7907/P2W6-3155", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:5658", "collection": "thesis", "collection_id": "5658", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03302010-131151765", "primary_object_url": { "basename": "Gerstell_mf_1995.pdf", "content": "final", "filesize": 4399813, "license": "other", "mime_type": "application/pdf", "url": "/5658/1/Gerstell_mf_1995.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Part 1. Two radiative transfer models with terrestial applications. Part 2. Testing the porcupine plate hypothesis", "author": [ { "family_name": "Gerstell", "given_name": "Marguerite F.", "clpid": "Gerstell-Marguerite-F" } ], "thesis_advisor": [ { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "thesis_committee": [ { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Paper I: Goody's convolution theorem for obtaining the cumulative k-distribution of a gas mixture requires stronger assumptions than the multiplicative property of band transmission; thus new experimental investigations of its effectiveness were undertaken. The convolution was found to be a useful speed optimization of k-distribution calculations at high pressures. For low pressures a variety of mixing methods were compared, all taking advantage of the idea that stratospheric lines are too narrow to overlap.\r\n\r\nAppendix I discusses the context and application of k-distribution calculations.\r\n\r\nPaper II: We used a \"quasi-random\" radiative transfer model to estimate stratospheric radiative perturbations produced by SO_2 gas, silicate ash, and H_2SO_4 aerosols after the 1982 El Chichon eruptions. One week after the last eruption, net radiative heating perturbations exceeding 20 K/day were modeled at altitudes near 26 km. Silicate ash heating may have been balanced by global enhancement of stratospheric meridional circulation, with upward velocities of 1 cm/s near Chichon's latitude. Radiative forcing by silicate ash and SO_2 gas should be included in more comprehensive models of plume evolution. Particle size distributions inferred from ash fallout rates could be wrong if radiative heating is neglected.\r\n\r\nPaper III: Uncertainties in the solar spectrum can affect modeled net heating rates in the upper stratosphere by a factor of several. Variation among Antarctic surface albedo values in common use can affect modeled net heating rates in the lower stratosphere by tens of percent. Large uncertainties in polar cloud cover are less important to stratospheric heating models. I join Marcel Nicolet in urging support for a continuous solar observation program, and recommend that future intercomparisons of stratospheric radiation models prescribe a solar spectrum, to reveal other differences.\r\n\r\nAppendix 2 gives the details of some further validation and sensitivity tests for the quasi-random model.\r\n\r\nPaper IV: The Porcupine Plate was postulated in 1986 to explain difficulties in reconstructing anomalies 21 and 24 in the North Atlantic. Its main feature was thought to be a transpressive Eocene plate boundary along Charlie-Gibbs Fracture Zone. Eliminating data that could have been affected by subsequent movements of Greenland relative to North America leads to a picture that casts doubt on the Porcupine Plate hypothesis.\r\n", "doi": "10.7907/e7ex-9x13", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:5658", "collection": "thesis", "collection_id": "5658", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03302010-131151765", "primary_object_url": { "basename": "Gerstell_mf_1995.pdf", "content": "final", "filesize": 4399813, "license": "other", "mime_type": "application/pdf", "url": "/5658/1/Gerstell_mf_1995.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Part 1. Two radiative transfer models with terrestial applications. Part 2. Testing the porcupine plate hypothesis", "author": [ { "family_name": "Gerstell", "given_name": "Marguerite F.", "clpid": "Gerstell-Marguerite-F" } ], "thesis_advisor": [ { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "thesis_committee": [ { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Paper I: Goody's convolution theorem for obtaining the cumulative k-distribution of a gas mixture requires stronger assumptions than the multiplicative property of band transmission; thus new experimental investigations of its effectiveness were undertaken. The convolution was found to be a useful speed optimization of k-distribution calculations at high pressures. For low pressures a variety of mixing methods were compared, all taking advantage of the idea that stratospheric lines are too narrow to overlap.\r\n\r\nAppendix I discusses the context and application of k-distribution calculations.\r\n\r\nPaper II: We used a \"quasi-random\" radiative transfer model to estimate stratospheric radiative perturbations produced by SO_2 gas, silicate ash, and H_2SO_4 aerosols after the 1982 El Chichon eruptions. One week after the last eruption, net radiative heating perturbations exceeding 20 K/day were modeled at altitudes near 26 km. Silicate ash heating may have been balanced by global enhancement of stratospheric meridional circulation, with upward velocities of 1 cm/s near Chichon's latitude. Radiative forcing by silicate ash and SO_2 gas should be included in more comprehensive models of plume evolution. Particle size distributions inferred from ash fallout rates could be wrong if radiative heating is neglected.\r\n\r\nPaper III: Uncertainties in the solar spectrum can affect modeled net heating rates in the upper stratosphere by a factor of several. Variation among Antarctic surface albedo values in common use can affect modeled net heating rates in the lower stratosphere by tens of percent. Large uncertainties in polar cloud cover are less important to stratospheric heating models. I join Marcel Nicolet in urging support for a continuous solar observation program, and recommend that future intercomparisons of stratospheric radiation models prescribe a solar spectrum, to reveal other differences.\r\n\r\nAppendix 2 gives the details of some further validation and sensitivity tests for the quasi-random model.\r\n\r\nPaper IV: The Porcupine Plate was postulated in 1986 to explain difficulties in reconstructing anomalies 21 and 24 in the North Atlantic. Its main feature was thought to be a transpressive Eocene plate boundary along Charlie-Gibbs Fracture Zone. Eliminating data that could have been affected by subsequent movements of Greenland relative to North America leads to a picture that casts doubt on the Porcupine Plate hypothesis.\r\n", "doi": "10.7907/e7ex-9x13", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4372", "collection": "thesis", "collection_id": "4372", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11022007-093001", "type": "thesis", "title": "Seismic Strain Rates and the State of Tectonic Stress in the Southern California Region", "author": [ { "family_name": "Huang", "given_name": "Weishi", "clpid": "Huang-Weishi" } ], "thesis_advisor": [ { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" } ], "thesis_committee": [ { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Allen", "given_name": "Clarence R.", "clpid": "Allen-C-R" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "I determine 505 fault plane solutions from the first motions of P-waves for the\r\nbackground seismicity (3.0≤ M≤6.0, 1981-1991) and collect mechanisms of major\r\nearthquakes (M≥6.0, 1927-1994) from the literature in the southern California region.\r\nThen I study the seismic strain and tectonic stress fields in individual domains (ten in\r\ntotal) by analyzing these mechanism data. The seismic strain tensors are obtained by\r\ntensorial summation of individual seismic moment tensors. The tectonic stress tensors\r\nare determined by performing numerical inversions of the slip vector data, using\r\nAngelier's (1990) method. The findings are summarized as follows:
\r\n\r\n(1) Of the 505 fault plane solutions for the 1981-1991 background seismicity, 54%\r\nare strike-slip (SF), 21 % reverse (RF), 17% normal (NF), and 8% oblique-slip\r\nfaulting (OS) events. The catalog of the major earthquakes for the period 1927-\r\n1994 also displays similar proportions of the faulting mechanisms;
\r\n\r\n(2) The similarity of the focal mechanisms can be measured by a parameter, seismic\r\nconsistency (Sc) introduced by Apperson (1991). It is defined as the ratio of the\r\nscalar moment of the total moment tensor to the sum of the scalar moments of\r\nindividual moment tensors. In southern California, the Brawley fault (BYF)\r\ndomain shows the highest Sc (0.70), whereas the White Wolf fault (WWF)\r\ndomain displays the lowest Sc (0.44). Sc values in other domains vary between\r\nthe above two values;
\r\n\r\n(3) The depths of possible low-angle faults inferred from the fault plane solutions\r\nvary from 20 km in the Transverse ranges where N-S convergence dominates, to\r\nonly 1 km in the southern Sierra Nevada fault (SSNF) domain where E-W divergence\r\ndominates. Our current data do not show the existence of a sigle unified\r\nseismically-active master detachment in the seismogenic zone;
\r\n\r\n(4) The axes of the maximum principal stress, \u03b41. are oriented N6\u00b0E \u00b111\u00b0, whereas\r\nthose of the maximum principal strain, \u03b51 are oriented N5\u00b0E \u00b121\u00b0;
\r\n\r\n(5) The strain and stress tensors are similar to each other in the Mojave (MVE), San\r\nJacinto (SJF), Elsinore (ESF), BYF, western and eastern Transverse Ranges\r\n(WTR, ETR) domains, but dissimilar in the central Transverse Ranges (CTR),\r\nNewport-Inglewood fault (NIF), WWF, and SSNF domains. Areas with small\r\nvalues of \u03a6 = (\u03b42 - \u03b43)/(\u03b41 - \u03b43) (<0.35) such as the WTR, CTR, and NIF domains are associated with more than 40% of RF events. Areas with \u03a6 values around 0.5\r\nsuch as the SJF, ETR, WWF, ESF, BYF, and MVE domains are associated with\r\nmore than 47% of SF events. The SSNF domain has a large \u03a6 (>0.65) and\r\nshows 49% of NF events, Variation of the state of stress appears to be in the\r\nTransverse Ranges where hypocenters are generally deep. Other areas show a\r\nrelatively stable state of stress throughout the seismogenic depth;
\r\n\r\n(6) Seismic fraction of deformation, \u03b7, is a measure of the deformation mode. It is\r\ndefined as the ratio of seismic strain rate to the total deformation rate. Because of\r\nthe limited seismic data, we can usually estimate the apparent instead of the real\r\nseismic fraction of deformation. Therefore, caution must be exercised in applying\r\nthe values of \u03b7 to evaluations of seismic potential, In southern California, there\r\nare some indications that areas in which seismic deformation nearly accounts for\r\nthe total deformation are typically associated with cold and rigid batholithic rocks\r\nor high seismic velocity anomalies such as in the SJF, south central MVE, WWF,\r\nand possibly the ETR domains. However, areas with low seismic velocity\r\nanomalies are not free of earthquakes as seen, for example, in the BYF domain,\r\nwhich shows \u03b7 = 0.6-1.0. Other domains show \u03b7 < 0.4. The problem of whether the\r\nmissing deformation is being released aseismically or has accumulated elastically\r\nremains to be resolved.
", "doi": "10.7907/P2W6-3155", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:7525", "collection": "thesis", "collection_id": "7525", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03182013-160237674", "primary_object_url": { "basename": "Keszthelyi_lp_1994.pdf", "content": "final", "filesize": 51471055, "license": "other", "mime_type": "application/pdf", "url": "/7525/1/Keszthelyi_lp_1994.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "On the Thermal Budget of Pahoehoe Lava Flows", "author": [ { "family_name": "Keszthelyi", "given_name": "L\u00e1szl\u00f3 P.", "clpid": "Keszthelyi-L\u00e1szl\u00f3-P" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Denlinger", "given_name": "Roger", "clpid": "Denlinger-R" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this thesis I investigate some aspects of the thermal budget of pahoehoe lava\r\nflows. This is done with a combination of general field observations, quantitative\r\nmodeling, and specific field experiments. The results of this work apply to pahoehoe\r\nflows in general, even though the vast bulk of the work has been conducted on the lavas\r\nformed by the Pu'u 'O'o - Kupaianaha eruption of Kilauea Volcano on Hawai'i. The field\r\nobservations rely heavily on discussions with the staff of the United States Geological\r\nSurvey's Hawaiian Volcano Observatory (HVO), under whom I labored repeatedly in\r\n1991-1993 for a period totaling about 10 months.
\r\n\r\nThe quantitative models I have constructed are based on the physical processes\r\nobserved by others and myself to be active on pahoehoe lava flows. By building up these\r\nmodels from the basic physical principles involved, this work avoids many of the pitfalls of\r\nearlier attempts to fit field observations with \"intuitively appropriate\" mathematical\r\nexpressions. Unlike many earlier works, my model results can be analyzed in terms of the\r\ninteractions between the different physical processes. I constructed models to: (1) describe\r\nthe initial cooling of small pahoehoe flow lobes and (2) understand the thermal budget of\r\nlava tubes.
\r\n\r\nThe field experiments were designed either to validate model results or to constrain\r\nkey input parameters. In support of the cooling model for pahoehoe flow lobes, attempts\r\nwere made to measure: (1) the cooling within the flow lobes, (2) the amount of heat\r\ntransported away from the lava by wind, and (3) the growth of the crust on the lobes.\r\nField data collected by Jones [1992], Hon et al. [1994b], and Denlinger [Keszthelyi and\r\nDenlinger, in prep.] were also particularly useful in constraining my cooling model for\r\nflow lobes. Most of the field observations I have used to constrain the thermal budget of\r\nlava tubes were collected by HVO (geological and geophysical monitoring) and the Jet\r\nPropulsion Laboratory (airborne infrared imagery [Realmuto et al., 1992]). I was able to\r\nassist HVO for part of their lava tube monitoring program and also to collect helicopterborne\r\nand ground-based IR video in collaboration with JPL [Keszthelyi et al., 1993].
\r\n\r\nThe most significant results of this work are (1) the quantitative demonstration that\r\nthe emplacement of pahoehoe and 'a'a flows are the fundamentally different, (2)\r\nconfirmation that even the longest lava flows observed in our Solar System could have\r\nformed as low effusion rate, tube-fed pahoehoe flows, and (3) the recognition that the\r\natmosphere plays a very important role throughout the cooling of history of pahoehoe lava\r\nflows. In addition to answering specific questions about the thermal budget of tube-fed\r\npahoehoe lava flows, this thesis has led to some additional, more general, insights into the\r\nemplacement of these lava flows. This general understanding of the tube-fed pahoehoe\r\nlava flow as a system has suggested foci for future research in this part of physical\r\nvolcanology.
", "doi": "10.7907/G5V5-T293", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:7525", "collection": "thesis", "collection_id": "7525", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03182013-160237674", "primary_object_url": { "basename": "Keszthelyi_lp_1994.pdf", "content": "final", "filesize": 51471055, "license": "other", "mime_type": "application/pdf", "url": "/7525/1/Keszthelyi_lp_1994.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "On the Thermal Budget of Pahoehoe Lava Flows", "author": [ { "family_name": "Keszthelyi", "given_name": "L\u00e1szl\u00f3 P.", "clpid": "Keszthelyi-L\u00e1szl\u00f3-P" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Denlinger", "given_name": "Roger", "clpid": "Denlinger-R" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this thesis I investigate some aspects of the thermal budget of pahoehoe lava\r\nflows. This is done with a combination of general field observations, quantitative\r\nmodeling, and specific field experiments. The results of this work apply to pahoehoe\r\nflows in general, even though the vast bulk of the work has been conducted on the lavas\r\nformed by the Pu'u 'O'o - Kupaianaha eruption of Kilauea Volcano on Hawai'i. The field\r\nobservations rely heavily on discussions with the staff of the United States Geological\r\nSurvey's Hawaiian Volcano Observatory (HVO), under whom I labored repeatedly in\r\n1991-1993 for a period totaling about 10 months.
\r\n\r\nThe quantitative models I have constructed are based on the physical processes\r\nobserved by others and myself to be active on pahoehoe lava flows. By building up these\r\nmodels from the basic physical principles involved, this work avoids many of the pitfalls of\r\nearlier attempts to fit field observations with \"intuitively appropriate\" mathematical\r\nexpressions. Unlike many earlier works, my model results can be analyzed in terms of the\r\ninteractions between the different physical processes. I constructed models to: (1) describe\r\nthe initial cooling of small pahoehoe flow lobes and (2) understand the thermal budget of\r\nlava tubes.
\r\n\r\nThe field experiments were designed either to validate model results or to constrain\r\nkey input parameters. In support of the cooling model for pahoehoe flow lobes, attempts\r\nwere made to measure: (1) the cooling within the flow lobes, (2) the amount of heat\r\ntransported away from the lava by wind, and (3) the growth of the crust on the lobes.\r\nField data collected by Jones [1992], Hon et al. [1994b], and Denlinger [Keszthelyi and\r\nDenlinger, in prep.] were also particularly useful in constraining my cooling model for\r\nflow lobes. Most of the field observations I have used to constrain the thermal budget of\r\nlava tubes were collected by HVO (geological and geophysical monitoring) and the Jet\r\nPropulsion Laboratory (airborne infrared imagery [Realmuto et al., 1992]). I was able to\r\nassist HVO for part of their lava tube monitoring program and also to collect helicopterborne\r\nand ground-based IR video in collaboration with JPL [Keszthelyi et al., 1993].
\r\n\r\nThe most significant results of this work are (1) the quantitative demonstration that\r\nthe emplacement of pahoehoe and 'a'a flows are the fundamentally different, (2)\r\nconfirmation that even the longest lava flows observed in our Solar System could have\r\nformed as low effusion rate, tube-fed pahoehoe flows, and (3) the recognition that the\r\natmosphere plays a very important role throughout the cooling of history of pahoehoe lava\r\nflows. In addition to answering specific questions about the thermal budget of tube-fed\r\npahoehoe lava flows, this thesis has led to some additional, more general, insights into the\r\nemplacement of these lava flows. This general understanding of the tube-fed pahoehoe\r\nlava flow as a system has suggested foci for future research in this part of physical\r\nvolcanology.
", "doi": "10.7907/G5V5-T293", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" } ]