Source Mechanisms Of Earthquakes

An innovative new approach to studying earthquake source mechanisms, combining theory and observation, for graduate students, researchers and seismology professionals.

Kostrov and Das present a general theoretical model summarizing our current knowledge of fracture mechanics as applied to earthquakes and earthquake source processes. Part I explains continuum and fracture mechanics, providing the reader with some background and context. Part II continues with a discussion of the inverse problem of earthquake source theory and a description of the seismic moment tensor. Part III presents specific earthquake source models. Although data processing and acquisition techniques are discussed only in simplified form for illustrative purposes, the material in this book will aid in better orienting and developing these techniques. The aim of this book is to explore the phenomena underlying earthquake fracture and present a general theoretical model for earthquake source processes.

nesus, Armenia, and Georgia have largely profited from the experience acquired in the study of the large events of the early 1980s. The Mediterranean region is not only the site of shallow dispersed seismic activity, it is also the site of localized intermediate depth seismic activity, and of some rare deeper events. Active subduc tion is clearly at the origin of Greek intermediate depth seismicity, while the deep activity under Calabria and the Vrancea region in Romania is clearly related to downgoing slabs that have long remained active after the arrest of subduction. The origin of the intermediate and very deep seismicity below Spain is a considerably more complex problem. Several possible explanations of the intermediate depth activity to about 110 km have been proposed, but the origin of the deep (650 km) events studied by BURFORN et a1. remains a mystery since this is the only source of deep activity that is not related in an obvious way to a subduction zone. The problem of seismic source mechanism and seismotectonics cannot be completely separated from that of the mechanical origin of earthquakes. Recent work on this subject has revealed the intimate relation between fault geometry, as observed by field geologists, and the results of inversion of source process from seismic data in the far-field or in the near-field.

Consisting of more than 150 articles written by leading experts, this authoritative reference encompasses the entire field of solid-earth geophysics. It describes in detail the state of current knowledge, including advanced instrumentation and techniques, and focuses on important areas of exploration geophysics. It also offers clear and complete coverage of seismology, geodesy, gravimetry, magnetotellurics and related areas in the adjacent disciplines of physics, geology, oceanography and space science.

Among all the numerical methods in seismology, the finite-difference (FD) technique provides the best balance of accuracy and computational efficiency. This book offers a comprehensive introduction to FD and its applications to earthquake motion. Using a systematic tutorial approach, the book requires only undergraduate degree-level mathematics and provides a user-friendly explanation of the relevant theory. It explains FD schemes for solving wave equations and elastodynamic equations of motion in heterogeneous media, and provides an introduction to the rheology of viscoelastic and elastoplastic media. It also presents an advanced FD time-domain method for efficient numerical simulations of earthquake ground motion in realistic complex models of local surface sedimentary structures. Accompanied by a suite of online resources to help put the theory into practice, this is a vital resource for professionals and academic researchers using numerical seismological techniques, and graduate students in earthquake seismology, computational and numerical modelling, and applied mathematics.

This book first focuses on the explanation of the theory about focal mechanisms and moment tensor solutions and their role in the modern seismology. The second part of the book compiles several state-of-the-art case studies in different seismotectonic settings of the planet.The assessment of seismic hazard and the reduction of losses due to future earthquakes is probably the most important contribution of seismology to society. In this regard, the understanding of reliable determination seismic source and of its uncertainty can play a key role in contributing to geodynamic investigation, seismic hazard assessment and earthquake studies. In the last two decades, the use of waveforms recorded at local-to-regional distances has increased considerably. Waveform modeling has been used also to estimate faulting parameters of small-to-moderate sized earthquakes.

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.