Seismic Waves And Sources

Earthquakes come and go as they please, leaving behind them trails of destruc tion and casualties. Although their occurrence is little affected by what we do or think, it is the task of earth scientists to keep studying them from all possible angles until ways and means are found to divert, forecast, and eventually control them. In ancient times people were awestruck by singular geophysical events, which were attributed to supernatural powers. It was recognized only in 1760 that earthquakes originated within the earth. A hundred years later, first systematic attempts were made to apply physical principles to study them. During the next century scientists accumulated knowledge about the effects of earthquakes, their geographic patterns, the waves emitted by them, and the internal constitution of the earth. During the past 20 years, seismology has made a tremendous progress, mainly because of the advent of modern computers and improvements in data acquisi tion systems, which are now capable of digital and analog recording of ground motion over a frequency range of five orders of magnitude. These technologic developments have enabled seismologists to make measurements with far greater precision and sophistication than was previously possible. Advanced computational analyses have been applied to high-quality data and elaborate theoretical models have been devised to interpret them. As a result, far reaching advances in our knowledge of the earth's structure and the nature of earthquake sources have occurred.

To Seismology Second, Revised Edition 1979 Springer Basel AG First published under Markus Bath, Introduktion till Seism%gin by Natur och Kultur Stockholm © 1970, Markus Bath and Bokforlaget Natur och Kultur, Stockholm CIP-Kurztitelaufnahme der Deutschen Bibliothek Bath, Markus: Introduction to seismology / Markus Bath. - 2., rev. ed. (Wissenschaft und Kultur; Bd. 27) Einheitssacht. : Introduktion till seismologin (dt.) ISBN 978-3-0348-5285-2 ISBN 978-3-0348-5283-8 (eBook) DOI 10. 1007/978-3-0348-5283-8 All rights reserved No part of this book may be reproduced by any means, nor transmitted, nor translated into a machine language without the written permission of the publisher English translation © 1973, 1979 Springer Basel AG Urspriinglich erschienen bei Birkhlluser Verlag Basel 1979 Softcover reprint of tbe hardcover 2nd edition 1979 ISBN 978-3-0348-5285-2 The data must be greatly amplified Preface and strengthened. to the First Edition BE NO GUTENBERG (1959) The purpose of this book is to give a popular review of modern seismology, its research methods, problems of current interest and results and also to some extent to elucidate the historical background. Especially in recent years, seismology has attracted much interest from the general public as well as from news agencies. The reasons for this are partly con nected with recordings of large explosions (nuclear tests), partly related to earthquake catastrophes. This interest and the questions which people have asked us for the past years have to a certain extent served as a sti mulus in the preparation of this book.

Methods in Computational Physics, Volume 12: Seismology: Body Waves and Sources is a six-chapter text that covers the numerical solution of some major problems on seismic body wave propagation and generation in the Earth. Chapter 1 considers the power of the computer to trace out detailed seismic response by means of ray theory, based from the results gathered in Soviet Union and the Continent. Chapter 2 exposes the finite difference methods employed to obtain complete theoretical seismograms for a source in a layered half-space, in wedges, and in a sphere, along with an outline of normal mode solutions for a source in a sphere and the ray expansion method. Chapter 3 discusses the theory and method of solution of the signals diffracted by the Earth's core using the response integral, the differential equations, and boundary conditions. This chapter deals also with the method of finding numerically the reflection coefficient in an inhomogeneous model. Chapter 4 describes a method for finding seismic velocity distributions that fit a given set of data and having found such distributions how to quantitatively assess their degree of uncertainty, such as their uniqueness. Chapter 5 surveys the theory of an observational technique for studying earthquake mechanism, while Chapter 6 provides a summary of theories of seismology and the important computational techniques together with some of their applications to seismic-source studies. This book will be greatly appreciated by geoscientists, physicists, and mathematicians.

Seismic waves – generated both by natural earthquakes and by man-made sources – have produced an enormous amount of information about the Earth's interior. In classical seismology, the Earth is modeled as a sequence of uniform horizontal layers (or sperical shells) having different elastic properties and one determines these properties from travel times and dispersion of seismic waves. The Earth, however, is not made of horizontally uniform layers, and classic seismic methods can take large-scale inhomogeneities into account. Smaller-scale irregularities, on the other hand, require other methods. Observations of continuous wave trains that follow classic direct S waves, known as coda waves, have shown that there are heterogeneities of random size scattered randomly throughout the layers of the classic seismic model. This book focuses on recent developments in the area of seismic wave propagation and scattering through the randomly heterogeneous structure of the Earth, with emphasis on the lithosphere. The presentation combines information from many sources to present a coherent introduction to the theory of scattering in acoustic and elastic materials and includes analyses of observations using the theoretical methods developed.

Seismic waves - generated both by natural earthquakes and by man-made sources - have produced an enormous amount of information about the Earth's interior. In classical seismology, the Earth is modeled as a sequence of uniform horizontal layers (or spherical shells) having different elastic properties and one determines these properties from travel times and dispersion of seismic waves. The Earth, however, is not made of horizontally uniform layers, and classic seismic methods can take large-scale inhomogeneities into account. Smaller-scale irregularities, on the other hand, require other methods. Observations of continuous wave trains that follow classic direct S waves, known as coda waves, have shown that there are heterogeneities of random size scattered randomly throughout the layers of the classic seismic model. This book focuses on recent developments in the area of seismic wave propagation and scattering through the randomly heterogeneous structure of the Earth, with emphasis on the lithosphere. The presentation combines information from many sources to present a coherent introduction to the theory of scattering in acoustic and elastic materials and includes analyses of observations using the theoretical methods developed. The second edition especially includes new observational facts such as the spatial variation of medium inhomogeneities and the temporal change in scattering characteristics and recent theoretical developments in the envelope synthesis in random media for the last ten years. Mathematics is thoroughly rewritten for improving the readability. Written for advanced undergraduates or beginning graduate students of geophysics or planetary sciences, this book should also be of interest to civil engineers, seismologists, acoustical engineers, and others interested in wave propagation through inhomogeneous elastic media.

This volume contains an extensive presentation of the theory, phenomenology and interpretation of seismic waves produced by natural and artificial sources. Each theoretical topic discussed in the book is presented in a self-contained and mathematically rigorous form, yet without excessive demands on the reader's mathematical background. It is the only book to include such a complete presentation of the mathematical background and modern developments of the WKBJ theory of seismic waves, and detailed discussions of its wide ranging applications. The book will therefore be useful to postgraduate students and research workers specialising in seismic wave theory, theoretical seismology, electromagnetic wave theory and other fields of wave propagation theory.

The special issue contains contributions presented at the international workshop Seismic waves in laterally inhomo- geneous media IV, which was held at the Castle of Trest, Czech Republic, May 22-27, 1995. The workshop, which was attended by about 100 seismologists from more than 10 countries, was devoted mainly to the current state of theoretical and computational means of study of seismic wave propagation in complex structures. The special issue can be of interest for theoretical, global and explorational seismologists. The first part contains papers dealing with the study and the use of various methods of solving forward and inverse problems in complicated structures. Among other methods, discrete-wave number method, the finite-difference method, the edge-wave supperposition method and the ray method are studied and used. Most papers contained in the second part are related to the ray method. The most important topics are two-point ray tracing, grid calculations of travel times and amplitudes and seismic wave propagation in anisotropic media.