Book Review
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ure and Applied Geophysics
Book Review Seismic Wave Propagation and Scattering in the Heterogeneous Earth, by H. Sato, M. C. Fehler and T. Maeda, Second Edition, Springer, 2012; ISBN: 978-3-642-23028-8, USD 229.00 PETROS MPOGIATZIS1 Horace Lamb, in 1903 calculated the first synthetic seismogram from a point source in a homogeneous half-space. The resulted seismogram was exceptionally simple, not containing (i.e., explaining) the complexity of observed seismograms. Since then, advances in theory and computational power allowed the consideration of more complex media, starting from layered Earth models like PREM and, recently, utilizing full 3D deterministic structure. However, the long lasting wave trains recorded after the direct arrivals, called coda-waves, cannot be explained completely from deterministic models. This book focuses on this less famous part of the seismograms, which arises from randomly distributed small-scale heterogeneities of arbitrary sizes, shapes, and other fluctuations of physical properties. These incoherent waves can be modeled only through stochastic methods, since it is impossible to consider or even represent deterministically every single short-scale heterogeneity that may be affecting them. Stochastic modeling is essential and is complementary to deterministic methods in explaining seismograms and describing Earth’s structure. The book is nicely organized into 11 chapters. After a small introductory first chapter, it begins practically from chapter 2 with a quick overview of several observations that indicate the existence of random heterogeneity, especially in the lithosphere. Also introduced here are the basic mathematical tools to describe random media, such as the common
1 Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA. E-mail: petrosbogiatzis@fas. harvard.edu
autocorrelation function (ACF) and the common power spectral density function (PSDF). In chapter 3, the coda-excitation problem is examined from the phenomenological point of view, and various coda excitation models are introduced and evaluated. Afterwards, the coda normalization method is described, and the chapter finishes with the presentation of spatial and temporal changes of medium heterogeneities and other parameters as they are observed from coda analysis. The fourth chapter deals with the mathematics of wave propagation and scattering in elastic media. The authors present here the Born approximation method for both scalar and vector elastic waves, starting from the deterministic case and moving to randomly heterogeneous media, where stochastic treatment is necessary. They also introduce the calculation of scattering coefficients from the PSDF of the velocity random variation of the medium. The fifth chapter discuses highfrequency wave attenuation, focused again in Earth’s lithosphere. Seismic attenuation is typically regarded as a combination of intrinsic mechanisms and scattering effects. The authors first present the proposed mechanisms of intrinsic attenuation, and afterwards
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