Imaging The Rupture Processes Of Earthquakes Using The Relative Back Projection Method

This thesis adopts the relative back-projection method to dramatically reduce “swimming” artifacts by identifying the rupture fronts in the time window of a reference station; this led to a faster and more accurate image of the rupture processes of earthquakes. Mitigating the damage caused by earthquakes is one of the primary goals of seismology, and includes saving more people’s lives by devising seismological approaches to rapidly analyze an earthquake’s rupture process. The back-projection method described in this thesis can make that a reality.

Investigation of earthquake source parameters is important for better understanding of the physics behind earthquakes, which is essential for mitigating the hazards of destructive earthquakes. This dissertation explores several different aspects of source parameter estimation. First, I image the rupture process of the 2004 M6.0 Parkfield earthquake in three dimensions using a waveform back-projection method. I identify a distinct secondary high-frequency phase that radiated from a point about 13 km northwest of the hypocenter. Together with existing slip model inversions of the Parkfield earthquake, these results constrain several physical properties of the rupture process. Second, I use an iterative least-squares approach on both local and global seismic data to isolate source spectra from attenuation and near-station site effects and apply an empirical Green's function correction for near-source attenuation. Brune-type stress drop estimates for small earthquakes in the Parkfield area and for moderate to large earthquakes worldwide range from 0.1 to 50 MPa, with robust lateral variations in average stress drop. In Parkfield some of these variations change temporally after the 2004 M6.0 Parkfield earthquake. On a global scale, the stress drop variations are usually confined to specific plate boundaries or tectonic regimes. The highest average stress drops occur for oceanic transform fault earthquakes and other strike-slip events. Intraplate events have a factor of two higher average stress drops than interplate events. Stress drops of both small earthquakes in Parkfield and larger global earthquakes show no dependence on moment. Our stress-drop estimates, combined with other published results, provide strong evidence that earthquakes exhibit self-similarity over most of the instrumentally observable magnitude range. Finally, using the spectral separation method to discriminate between natural seismicity and man-made explosions, I find that the best single waveform discriminant for data recorded in southern California is the RMS-misfit between quarry blast spectra and an w-2 source model.

This book presents the kinematic earthquake rupture studies from moment tenor to spatial-temporal rupture imaging. For real-time seismic hazard monitoring, the new stable automatic moment tensor (AutoBATS) algorithm is developed and implemented for the real-time MT reports by the Taiwan Earthquake Science Information System (TESIS). In order to understand the rupture behavior of the 2013 Mw 8.3 Okhotsk deep earthquake sequence, the 3D MUltiple SIgnal Classification Back Projection (MUSIC BP) with P and pP phases is applied. The combined P- and pP-wave BP imaging of the mainshock shows two stages of anti-parallel ruptures along two depths separating for about 10~15 km. Unusual super-shear ruptures are observed through the 3D BP images of two Mw 6.7 aftershocks. In last two chapters, the 3D BP imaging reveals similar rupture properties of two shallow catastrophic earthquakes (Mw=6.4) in southwestern Taiwan. Both the 2010 Jiashian and 2016 Meinong earthquakes ruptured westward with similar velocity of ~2.5 km/s along a NE-ward shallow dipping blind fault. The rupture similarities of the doublet suggest two parallel elongate asperities along the causative fault. After several decades of seismic quiescence, the 2010 Jiashian event initiated the rupture at the deeper asperity and triggered the shallower asperity which caused catastrophes six years later.

Treatise on Geophysics, Second Edition, is a comprehensive and in-depth study of the physics of the Earth beyond what any geophysics text has provided previously. Thoroughly revised and updated, it provides fundamental and state-of-the-art discussion of all aspects of geophysics. A highlight of the second edition is a new volume on Near Surface Geophysics that discusses the role of geophysics in the exploitation and conservation of natural resources and the assessment of degradation of natural systems by pollution. Additional features include new material in the Planets and Moon, Mantle Dynamics, Core Dynamics, Crustal and Lithosphere Dynamics, Evolution of the Earth, and Geodesy volumes. New material is also presented on the uses of Earth gravity measurements. This title is essential for professionals, researchers, professors, and advanced undergraduate and graduate students in the fields of Geophysics and Earth system science. Comprehensive and detailed coverage of all aspects of geophysics Fundamental and state-of-the-art discussions of all research topics Integration of topics into a coherent whole

Impacts and Insights of Gorkha Earthquake in Nepal offers a practical perspective on disaster risk management using lessons learned and considerations from the 2015 Gorkha earthquake in Nepal, which was the worst disaster to hit Nepal since the 1934 Nepal–Bihar earthquake. Using a holistic approach to examine seismicity, risk perception and intervention, the book serves as a detailed case study to improve disaster resilience globally, including social, technical, governmental and institutional risk perception, as well as scientific understanding of earthquake disasters. Covering the details of the Gorkha earthquake, including damage mapping and recovery tactics, the book offers valuable insights into ways forward for seismologists, earthquake researchers and engineers and policy-makers. Includes the latest status of seismic risk, risk perception, to-date interventions and historical scenarios in Nepal Examines details of Gorkha earthquake, including geo-seismicity, damage statistics, casualties, effect on cultural heritage, gender-risk mechanics, case studies of social institutions, urban-risk mechanics, rural-risk mechanics, resilience dimensions, social institutions in risk management, stories of resilience and failures and a critical review of efficacy of interventions in risk mitigation Offers future insights and ways forward in terms of risk reduction studies, socio-cultural dimensions of risk management, scientific intervention and policy making, implementation of existing frameworks and endorsement of resilient practices for Nepal Includes damage mapping in all affected areas

In seismology an earthquake source is described in terms of a fault with a particular rupture size. The faulting process of large earthquakes has been investigated in the last two decades through analyses of long-period seismo grams produced by advanced digital seismometry. By long-period far-field approximation, the earthquake source has been represented by physical parameters such as s~ismic moment, fault dimension and earthquake mag nitude. Meanwhile, destruction often results from strong ground motion due to large earthquakes at short distances. Since periods of strong ground motion are far shorter than those of seismic waves at teleseismic distances, the theory of long-period source process of earthquakes cannot be applied directly to strong ground motion at short distances. The excitation and propagation of high-frequency seismic waves are of special interest in recent earthquake seismology. In particular, the descrip tion and simulation of strong ground motion are very important not only for problems directly relevant to earthquake engineering, but also to the frac ture mechanics of earthquake faulting. Understanding of earthquake sources has been developed by investigating the complexity of faulting processes for the case of large earthquakes. Laboratory results on rock failures have also advanced the understanding of faulting mechanisms. Various attempts have been made to simulate, theoretically and empirically, the propagation of short-period seismic waves in the heterogeneous real earth.

Modern Global Seismology, Second Edition, is a complete, self-contained primer on seismology, featuring extensive coverage of all related aspects—from observational data through prediction—and emphasizing the fundamental theories and physics governing seismic waves, both natural and anthropogenic. Based on thoroughly class-tested material, the text provides a unique perspective on Earth’s large-scale internal structure and dynamic processes, particularly earthquake sources, and the application of theory to the dynamic processes of the earth’s upper layer. This insightful new edition is designed for accessibility and comprehension for graduate students entering the field. Exploration seismologists will also find it an invaluable resource on topics such as elastic-wave propagation, seismic instrumentation, and seismogram analysis. Includes more than 400 illustrations, from both recent and traditional research articles, to help readers visualize mathematical relationships, as well as boxed features to explain advanced topics Offers incisive treatments of seismic waves, waveform evaluation and modeling, and seismotectonics, as well as quantitative treatments of earthquake source mechanics and numerous examples of modern broadband seismic recordings Covers current seismic instruments and networks and demonstrates modern waveform inversion methods Includes extensive, updated references for further reading new to this edition Features reorganized chapters split into two sections, beginning with introductory content such as tectonics and seismogram analysis, and moving on to more advanced topics, including seismic wave excitation and propagation, multivariable and vector calculus, and tensor approaches Completely updated references and figures to bring the text up to date Includes all-new sections on recent advancements and to enhance examples and understanding Split into shorter chapters to allow more flexibility for instructors and easier access for researchers, and includes exercises