Crustal Deformation During Co And Postseismic Phases Of The Earthquake Cycle Inferred From Geodetic And Seismic Data PDF Download
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Author | : Mong-Han Huang |
Publisher | : |
Total Pages | : 180 |
Release | : 2014 |
Genre | : |
ISBN | : |
Download Crustal Deformation During Co- and Postseismic Phases of the Earthquake Cycle Inferred from Geodetic and Seismic Data Book in PDF, ePub and Kindle
The work presented in my dissertation focuses on the crustal deformation during the co- and postseismic periods in earthquake cycles. I use geodetic and seismic data to constrain and better understand the behavior of the earthquake source during the coseismic period. For the postseismic period, I use geodetic data to observe the surface displacements from centimeter-scale to millimeter-scale from an Mw 7.9 and Mw 6.9 event, respectively. I model different mechanisms to explain the postseismic deformation and to further constrain the crustal and upper mantle rheology. For the coseismic earthquake source study, I explore the source of the 2010 Mw 6.3 Jia-Shian, Taiwan earthquake. I develop finite-source models using a combination of seismic data (strong motion and broadband) and geodetic data (InSAR and GPS) to understand the rupture process and slip distribution of this event. The main shock is a thrust event with a small left-lateral component. Both the main shock and aftershocks are located in a transition zone where the depth of seismicity and an inferred regional basal detachment increases from central to southern Taiwan. The depth of this event and the orientation of its compressional axis suggest that this event involves the reactivation of a deep and weak pre-existing NW-SE geological structure. The 1989 Mw 6.9 Loma Prieta earthquake provides the first opportunity since the 1906 San Francisco (Mw 7.9) earthquake to study postseismic relaxation processes and estimate rheological parameters in the region with modern space geodetic tools. The first five years postseismic displacements can be interpreted to be due to aseismic right-oblique fault slip on or near the coseismic rupture, as well as thrusting up-dip of the rupture within the Foothills thrust belt. However, continuing transient surface displacements (d"5 mm/yr) until 2002 revealed by PSInSAR and GPS in the northern Santa Cruz Mountains may indicate a longer-term postseismic deformation. I model the viscoelastic relaxation of the lower crust and upper mantle following the Loma Prieta earthquake to explain the surface displacement. A 14-km-thick lower crust (16 - 30 km depth) viscosity of> 1019 Pa s and an upper mantle viscosity of ~1018 Pa s best explain the geodetic data. The weak upper mantle viscosity in this area is in good agreement with upper mantle rheology in southern California (0.46 - 5 × 1019 Pa s) using a similar approach from studying the postseismic deformation following the 1999 (Mw 7.1) Hector Mine earthquake. Periods of accelerated postseismic deformation following large earthquakes reflect the response of the Earth's lithosphere to sudden coseismic stress changes. I investigate postseismic displacements following the 2008 Wenchuan (Mw 7.9), China earthquake in eastern Tibet and probe the differences in rheological properties across the edge of the Tibetan Plateau. Based on nearly two years of GPS and InSAR measurements, I find that the shallow afterslip on the Beichuan Fault can explain the near-field displacements, and the far-field displacements can be explained by a viscoelastic lower crust beneath Tibet with an initial effective viscosity of 4.4 × 1017 Pa s and a long-term viscosity of 1018 Pa s. On the other hand, the Sichuan Basin block has a high-viscosity upper mantle (> 1020 Pa s) underlying an elastic 35-km-thick crust. The inferred strong contrast in lithospheric rheologies between the Tibetan Plateau and the Sichuan Basin is consistent with models of ductile lower crustal flow that predict maximum topographic gradients across the Plateau margins where viscosity differences are greatest. With additional 6-year-long continuous GPS measurements deployed in the eastern Tibetan Plateau and the Sichuan Basin, viscoelastic relaxation models with the same geometry setups suggests Tibetan lower crust with an initial effective viscosity of 9 × 1017 Pa s and steady-state viscosity of 1019 Pa s. I also use the laboratory experiments derived power law flow model to fit the postseismic deformation. The viscosity estimated from this model varies with material parameters (e.g. grain size, water content, etc.) as well as environmental parameters (temperature, pressure, background strain rate, etc.). The diffusion creep refers to the power law flow mainly controlled by the mineral grain size, and the dislocation creep refers to it mainly controlled by the background stress level. For a diffusion creep type of power law flow, a Tibetan crust composed of wet feldspar (water content = 1000 H/106Si; grain size = 1 - 4 mm) and upper mantle composed of wet olivine (water content = 200 H/106Si; grain size = ~2 mm) can predict the 6-year-long poseismic time series well. This result roughly agrees with rock mechanics laboratory experiments. The channel flow model predicts the plateau margins are steepest where the viscosity of the surrounding blocks are highest. The low viscosity in the Tibetan lower crust and the contrasting rheology across the plateau margin derived from postseismic deformation are consistent with the channel flow model.
Author | : Dorian Golriz |
Publisher | : |
Total Pages | : 0 |
Release | : 2023 |
Genre | : |
ISBN | : |
Download Seismogeodetic Studies of the Crustal Deformation Cycle for Hazards Mitigation Book in PDF, ePub and Kindle
This dissertation presents several studies focusing on the three phases of the crustal deformation cycle. Using an optimal combination of seismic and space geodetic techniques, we investigate the coseismic phase of an earthquake that includes both shaking and permanent displacements, the postseismic phase where additional slip may occur around the affected region, and the interseismic phase over which stress builds-up at the interface between tectonic plates. Studying the crustal deformation cycle has important implications for understanding tectonic fault zone processes such as slip partitioning and strain accumulation, and to improve real-time systems for tsunami and earthquake early warnings. We first apply a physics-based approach to identify the transition from coseismic to postseismic deformation, and show how early postseismic is significant just minutes to hours after an earthquake. Our results show that the widely used estimates of daily coseismic offsets can lead to an overprediction of earthquake coseismic displacements. We compare the commonly used daily offsets and our rapid coseismic window methodology over several earthquakes and demonstrate that without consideration of the early postseismic stages, both coseismic and postseismic fault slip models can be biased by several meters. We then use the coseismic time window analysis and rely on earthquake source theory to develop a rapid earthquake magnitude determination method. To test our approach, we simulate a real-time environment by replaying historical earthquakes around the Pacific basin. Our results show that we can reliably estimate earthquake magnitude over the 7.2
Author | : Tianhaozhe Sun |
Publisher | : |
Total Pages | : |
Release | : 2017 |
Genre | : |
ISBN | : |
Download Crustal Deformation Associated with Great Subduction Earthquakes Book in PDF, ePub and Kindle
The slip behaviour of subduction faults and the viscoelastic rheology of Earth's mantle govern crustal deformation throughout the subduction earthquake cycle. This Ph.D. dissertation presents research results on two topics: (1) coseismic and postseismic slip of the shallowest segment of subduction faults and (2) postseismic deformation following great subduction earthquakes controlled by mantle viscoelasticity. Topic 1: Slip behaviour of the shallowest subduction faults. By modelling high-resolution cross-trench bathymetry surveys before and after the 2011 Mw 9.0 Tohoku-oki earthquake, we determine the magnitude and distribution of coseismic slip over the most near-trench 40 km of the Japan Trench megathrust. The inferred > 60 m average slip and a gentle increase by 5 m towards the trench over this distance indicate moderate degree of net coseismic weakening of the shallow fault. Using near-trench seafloor and sub-seafloor fluid pressure variations as strain indicators in conjunction with land-based geodetic measurements, we determine coseismic-slip and afterslip distributions of the 2012 Mw 7.6 Costa Rica earthquake. Here, trench-breaching slip similar to the Tohoku-oki rupture did not occur during the earthquake, but afterslip extended to the trench axis and reached ~0.7 m over 1.3 years after the earthquake, exhibiting a velocity-strengthening behaviour. These two contrasting examples bracket a possibly wide range of slip behaviour of the shallow megathrust. They help us understand why large tsunamis are generated by some but not all subduction earthquakes. Topic 2: Postseismic deformation following great subduction earthquakes. Due to the asymmetry of megathrust rupture, with the upper plate undergoing greater coseismic tension than the incoming plate, viscoelastic stress relaxation causes the trench and land areas to move in opposite, opposing directions immediately after the earthquake. Seafloor geodetic measurements following the 2011 Tohoku-oki earthquake, modelled in this work, provided the first direct observational evidence for this effect. Systematic modelling studies in this work suggest that such viscoelastic opposing motion should be common to all Mw ≥ 8 subduction earthquakes. As the effect of viscoelastic relaxation decays with time and the effect of fault relocking becomes increasingly dominant, the dividing boundary of the opposing motion continues to migrate away from the rupture area. Comparative studies of ten 8 ≤ Mw ≤ 9.5 subduction earthquakes in this dissertation quantifies the primary role of earthquake size in controlling the "speed" of the evolution of this deformation. Larger earthquakes are followed by longer-lived opposing motion that affects a broader region of the upper plate.
Author | : Sylvain Barbot |
Publisher | : |
Total Pages | : 217 |
Release | : 2009 |
Genre | : |
ISBN | : |
Download Studies of Co- and Postseismic Deformation of the Lithosphere from Numerical Models and Space Geodetic Data Book in PDF, ePub and Kindle
In this dissertation, I study the co- and postseismic deformation of the lithosphere using numerical models of three-dimensional time-dependent deformation and space geodetic data. I derive an original approach to simulate the static deformation due to faulting and volcanic unrest in a heterogeneous half space with vertical and lateral variations in elastic moduli. The method is based on a semi-analytic elastic Green function in the Fourier domain. I extend the model to include time-dependent inelastic properties of the lithosphere. This approach can be used to model time series of poroelastic rebound, viscoelastic flow and fault creep, three important mechanisms thought to participate in postseismic transients. I use kinematic inversions and forward models of deformation to infer the postseismic mechanisms responsible for the transient that followed the 2003 Altai earthquake. I find that synthetic aperture radar (SAR) data are most compatible with afterslip. The absence of an observable viscoelastic relaxation in the three years following the earthquake can be explained by an effective viscosity of the ductile substrate greater than 1019 Pa s. I use numerical models of coseismic deformation to explain anomalously strained areas in the East California Shear Zone imaged by SAR line-of-sight (LOS) data in the vicinity of the 1992 Landers and 1999 Hector Mine earthquakes. I find that the enhanced strain can be explained by compliant zones (CZs) surrounding long-lived faults in the Mojave desert. The LOS data is best explained by a 50% reduction of rigidity in volumes of the order of 1-2 km thick around historical faults that extend from 5 km depth for the Calico CZ to 9 km depth for the Pinto Mountain CZ. Finally, I use kinematic inversion of GPS data and forward models to identify the location and rheology of the afterslip that followed the 2004 Parkfield earthquake. The time dependence and amplitude of GPS time series can be explained by slip on an asperity centered at 5 km depth and governed by a rate-strengthening friction with parameter (a-b)=7 x 10−3, compatible with values obtained from laboratory experiment. The GPS observations show evidence of lateral variations in the frictional properties on the Parkfield segment of the San Andreas fault.
Author | : National Science Foundation (U.S.) |
Publisher | : |
Total Pages | : 1108 |
Release | : |
Genre | : Engineering |
ISBN | : |
Download Summaries of Projects Completed Book in PDF, ePub and Kindle
Author | : Paul Segall |
Publisher | : Princeton University Press |
Total Pages | : 465 |
Release | : 2010-01-04 |
Genre | : Science |
ISBN | : 140083385X |
Download Earthquake and Volcano Deformation Book in PDF, ePub and Kindle
Earthquake and Volcano Deformation is the first textbook to present the mechanical models of earthquake and volcanic processes, emphasizing earth-surface deformations that can be compared with observations from Global Positioning System (GPS) receivers, Interferometric Radar (InSAR), and borehole strain- and tiltmeters. Paul Segall provides the physical and mathematical fundamentals for the models used to interpret deformation measurements near active faults and volcanic centers. Segall highlights analytical methods of continuum mechanics applied to problems of active crustal deformation. Topics include elastic dislocation theory in homogeneous and layered half-spaces, crack models of faults and planar intrusions, elastic fields due to pressurized spherical and ellipsoidal magma chambers, time-dependent deformation resulting from faulting in an elastic layer overlying a viscoelastic half-space and related earthquake cycle models, poroelastic effects due to faulting and magma chamber inflation in a fluid-saturated crust, and the effects of gravity on deformation. He also explains changes in the gravitational field due to faulting and magmatic intrusion, effects of irregular surface topography and earth curvature, and modern concepts in rate- and state-dependent fault friction. This textbook presents sample calculations and compares model predictions against field data from seismic and volcanic settings from around the world. Earthquake and Volcano Deformation requires working knowledge of stress and strain, and advanced calculus. It is appropriate for advanced undergraduates and graduate students in geophysics, geology, and engineering. Professors: A supplementary Instructor's Manual is available for this book. It is restricted to teachers using the text in courses. For information on how to obtain a copy, refer to: http://press.princeton.edu/class_use/solutions.html
Author | : |
Publisher | : |
Total Pages | : 1090 |
Release | : 1978 |
Genre | : Engineering |
ISBN | : |
Download Summaries of Projects Completed in Fiscal Year ... Book in PDF, ePub and Kindle
Author | : John S. Oldow |
Publisher | : Geological Society of America |
Total Pages | : 384 |
Release | : 2009 |
Genre | : Science |
ISBN | : 0813724473 |
Download Late Cenozoic Structure and Evolution of the Great Basin-Sierra Nevada Transition Book in PDF, ePub and Kindle
Author | : National Science Foundation (U.S.) |
Publisher | : |
Total Pages | : 1092 |
Release | : 1978 |
Genre | : Engineering |
ISBN | : |
Download Summaries of Projects Completed in Fiscal Year ... Book in PDF, ePub and Kindle
Author | : Duncan Carr Agnew |
Publisher | : |
Total Pages | : 32 |
Release | : 1995 |
Genre | : Earth |
ISBN | : |
Download Interpretation of Crustal Deformation Measurements in Southern California Book in PDF, ePub and Kindle