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DYNAMIC RUPTURE PROCESSES AND SEISMIC RADIATION IN MODELS OF
EARTHQUAKE FAULTS SEPARATING SIMILAR AND DISSIMIAR SOLIDS
by
Zheqiang Shi
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(GEOLOGICAL SCIENCES)
August 2009
Copyright 2009 Zheqiang Shi
Object Description
| Title | Dynamic rupture processes and seismic radiation in models of earthquake faults separating similar and dissimilar solids |
| Author | Shi, Zheqiang |
| Author email | zheqians@usc.edu; samzqshi@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Geological Sciences |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2009-04-29 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-08-04 |
| Advisor (committee chair) | Ben-Zion, Yehuda |
| Advisor (committee member) |
Jordan, Thomas H. Nakano, Aiichiro Sammis, Charles G. Becker, Thorsten W. |
| Abstract | This thesis examines dynamic ruptures along frictional interfaces and seismic radiation in models of earthquake faults separating similar and dissimilar solids with the goal of advancing the understanding of earthquake physics.; The dynamics of Mode-II rupture along an interface governed by slip-weakening friction between dissimilar solids are investigated. The results show that the wrinkle-like rupture along such interfaces evolves to unilateral propagation in the slip direction of the compliant side for a broad range of conditions, and the closer the initial shear stress is to the static friction the smaller degree of material contrast is needed for this evolution to occur. Transition of the wrinkle-like pulse to crack-like rupture occurs when the reduction of friction coefficient is sufficiently large.; Energy partition associated with various rupture modes along an interface governed by rate- and state-dependent friction between identical solids is investigated. The rupture mode changes with varying velocity dependence of friction, strength excess parameter and length of the nucleation zone. High initial shear stress and weak velocity dependence of friction favor crack-like ruptures, while the opposite conditions favor the pulse-like mode. The rupture mode can switch from a subshear single pulse to a supershear train of pulses when the width of the nucleation zone is increased. The elastic strain energy released over the same propagation distance by the different rupture modes has the order:supershear crack, subshear crack, supershear train-of-pulses and subshear single-pulse. General considerations and observations suggest that the subshear pulse and supershear crack are, respectively, the most and least common modes of earthquake ruptures.; The effect of plasticity and interface elasticity on dynamic frictional sliding along an interface induced by edge impact loading between two identical elastic-viscoplastic solids is analyzed. The material on each side is isotropically strain-hardening. The interface is characterized as having an elastic response together with an inelastic response characterized by rate- and state-dependent friction. The results show that bulk material plasticity tends to smooth out oscillations. Larger impact velocity induces more extensive plastic dissipation and larger effect on slip mode and energy partition. Also larger values of the interface shear stiffness tend to favor crack-like mode of sliding.; The last part of we examine the characteristics of seismic radiation from localized fault-opening and shear motions and the effect of having dissimilar solids across the fault on seismic radiation by employing calculations of synthetic seismograms generated at various receiver locations by shear and tensile dislocation sources. The existence of a velocity contrast across the fault produces complexities that mask somewhat the polarity and amplitude signals of body waves characteristic of the tensile dislocation. The recording and analysis of the discussed signals for regular earthquakes that are dominated by shear motion will require high-resolution receivers located very close to the fault. |
| Keyword | earthquakes; dynamic rupture; rupture pulses; crack propagation; supershear rupture; friction; frictional sliding; plasticity; bimaterial interface; earthquake energy; fault mechanics; seismic radiation; numerical simulations |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m2463 |
| Rights | Shi, Zheqiang |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Shi-3086 |
| Archival file | uscthesesreloadpub_Volume51/etd-Shi-3086.pdf |
Description
| Title | Page 1 |
| Full text | DYNAMIC RUPTURE PROCESSES AND SEISMIC RADIATION IN MODELS OF EARTHQUAKE FAULTS SEPARATING SIMILAR AND DISSIMIAR SOLIDS by Zheqiang Shi A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (GEOLOGICAL SCIENCES) August 2009 Copyright 2009 Zheqiang Shi |
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