Elastic Waves In Random Media

This book treats various generalizations of the classical O'Doherty-Anstey formula in order to describe stratigraphic filtering effects. These are the effects that can be observed when elastic and electromagnetic waves propagate through multilayered structures. Our aim was to treat this topic in a comprehensive manner and present compact results in a didactically simple way, emphasizing the physics of the wave-propagation phenomena. We do not claim mathematical rigidity in all our derivations, however, we are pleased to have obtained quite simple descriptions of scattering, transmission and reflection of wavefields in acoustic, elastic, and poroelastic media which can be useful for various seismological and non-seismological applications.

This book treats various generalizations of the classical O'Doherty-Anstey formula in order to describe stratigraphic filtering effects. These are the effects that can be observed when elastic and electromagnetic waves propagate through multilayered structures. Our aim was to treat this topic in a comprehensive manner and present compact results in a didactically simple way, emphasizing the physics of the wave-propagation phenomena. We do not claim mathematical rigidity in all our derivations, however, we are pleased to have obtained quite simple descriptions of scattering, transmission and reflection of wavefields in acoustic, elastic, and poroelastic media which can be useful for various seismological and non-seismological applications.

The past decade has witnessed breakthroughs in the understanding of the wave localization phenomena and its implications for wave multiple scattering in inhomogeneous media. This book brings together review articles written by noted researchers in this field in a tutorial manner so as to give the readers a coherent picture of its status. It would be valuable both as an up-to-date reference for active researchers as well as a readable source for students looking to gain an understanding of the latest results.

This volume contains a timely collection of research papers on the latest developments in the ever-increasing use of elastic waves in a variety of contexts. There are reports on wave-propagation in various types of media: in both isotropic and anisotropic bodies; in homogeneous and inhomogeneous media; in media with cracks or inclusions in random media; and in layered composites. The bulk of the papers are concerned with propagation in elastic media, but also included are viscoelastic, thermoelastic and magneto-electroelastic wave propagation, as well as waves in porous and piezo-electric bodies. Consideration is given to propagation in bodies as diverse as stretched elastic strings to surfaces such as thin walled cylinders, and thin films under stress. Applications considered include the determination of the depth of cracks; analysis of ground motions generated by a finite fault in seismology; surface wave spreading on piezo-electric solids; and dynamical stress intensity factors. Most of the papers are theoretical in nature, and many are complemented by numerical studies. Also included are a general survey on experimental techniques, and reports on experimental work. The volume will be of interest to those who do theoretical studies of elastic wave propagation and to those who apply elastic waves whether in seismology, non-destructive testing, the fabrication of devices or underwater acoustics, etc.

Seismic waves generated by earthquakes have been interpreted to provide us information about the Earth’s structure across a variety of scales. For short periods of less than 1 second, the envelope of seismograms changes significantly with increased travel distance and coda waves are excited by scattering due to randomly distributed heterogeneities in the Earth. Deterministic structures such as horizontally uniform velocity layer models in traditional seismology cannot explain these phenomena. This book focuses on the Earth heterogeneity and scattering effects on seismic waves. Topics covered are recent developments in wave theory and observation including: coda wave analysis for mapping medium heterogeneity and monitoring temporal variation of physical properties, radiation of short-period seismic waves from an earthquake fault, weak localization of seismic waves, attenuation of seismic waves in randomly porous media, synthesis of seismic wave envelopes in short periods, and laboratory investigations of ultrasonic wave propagation in rock samples. Understanding new methods for the analysis of short-period seismic waves to characterize the random heterogeneity of the Earth on many scales Observations of seismic wave scattering Discussion of techniques for mapping medium heterogeneity and for monitoring temporal change in medium characteristics Up-to-date techniques for the synthesis of wave envelopes in random media

This special issue contains contributions presented at the international workshop Seismic Waves in Laterally Inhomogeneous Media V, which was held at the Castle of Zahrádky, Czech Republic, June 5 - 9, 2000. The workshop, which was attended by about 60 seismologists from 16 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 begins with papers dealing with the study and the application of the ray methods. Problems such as coupling of quasi-shear waves or smoothing of models for effective ray computations are dealt with. Applications of the ray methods in seismic exploration are presented. Further, directional wavefield decomposition, phase space, path integral and parabolic equation methods are discussed. Attention is also devoted to attenuation and scattering problems, and to seismic inversion problems.

Elastic waves are used in fields as diverse as the non-destructive evaluation of materials, medicine, seismology and telecommunications. Elastic Waves in Solids 2 analyzes the radiation, scattering and generation of these waves. It studies the emission of bulk or surface waves from sources localized on the surface of an isotropic or anisotropic solid. It then examines the scattering of a longitudinal or transverse elastic wave by one or more cylindrical or spherical heterogeneities. Finally, it explores the methods and devices used to generate and detect elastic waves, using the piezoelectric effect or the interaction with a laser beam. Accompanying figures illustrate these properties, and the text provides the orders of magnitude of some characteristic parameters. This book is intended for students completing a master’s degree in acoustics, mechanics, geophysics or engineering, as well as teachers and researchers in these disciplines.

Reprint from Pure and Applied Geophysics (PAGEOPH), Volume 128 (1988), No. 1/2