Seismic waves are one of the standard diagnostic tools used to determine the mechanical parameters (volume density of mass, compressibility, elastic stiffness) in the interior of the earth and the geometry of subsurface structures. There is increasing evidence that in the interpretation of seismic data - especially shear-wave data - the influence of anisotropy must be taken into account.This volume presents a method to compute the seismic waves that are generated by an impulsive source in a stratified anisotropic medium. Although written with the seismic applications in mind, the method that is developed is not limited to solid-earth geophysics. In fact, the methods discussed in this monograph are applicable wherever waves propagate in stratified, anisotropic media. The standard approach to this problem is to employ Fourier transformations with respect to time and with respect to the horizontal spatial coordinates. To obtain numerical results, the relevant inverse transformations then have to be evaluated numerically. In this monograph the problem is, in contrast to the standard approach, solved by applying the Cagniard-de Hoop method and by representing the wave field as a sum of generalized rays. With this method, the computational results can be obtained relatively easily with any degree of accuracy, and with considerably less computation time. For completeness, analysis of acoustic waves in stratified isotropic media is included. Furthermore, for large horizontal or vertical source-receiver separations very efficient approximations are derived. Several examples and applications are given.

Among the variety of wave motions one can single out surface wave pr- agation since these surface waves often adjust the features of the energy transfer in the continuum (system), its deformation and fracture. Predicted by Rayleigh in 1885, surface waves represent waves localized in the vicinity ofextendedboundaries(surfaces)of?uidsorelasticmedia. Intheidealcase of an isotropic elastic half-space while the Rayleigh waves propagate along the surface, the wave amplitude (displacement) in the transverse direction exponentially decays with increasing distance away from the surface. As a resulttheenergyofsurfaceperturbationsislocalizedbytheRayleighwaves within a relatively narrow layer beneath the surface. It is this property of the surface waves that leads to the resonance phenomena that accompany the motion of the perturbation sources (like surface loads) with velocities close to the Rayleigh one; (see e. g. , R. V. Goldstein. Rayleigh waves and resonance phenomena in elastic bodies. Journal of Applied Mathematics and Mechanics (PMM), 1965, v. 29, N 3, pp. 608-619). It is essential to note that resonance phenomena are also inherent to the elastic medium in the case where initially there are no free (unloaded) surfaces. However, they occur as a result of an external action accompanied by the violation of the continuity of certain physical quantities, e. g. , by crack nucleation and dynamic propagation. Note that the aforementioned resonance phenomena are related to the nature of the surface waves as homogeneous solutions (eigenfunctions) of the dynamic elasticity equations for a half-space (i. e. nonzero solutions at vanishing boundary conditions).

No detailed description available for "Surface Waves and Discontinuities".

Following the breakthrough in the last decade in identifying the key parameters for time and depth imaging in anisotropic media and developing practical methodologies for estimating them from seismic data, Seismic Signatures and Analysis of Reflection Data in Anisotropic Media primarily focuses on the far reaching exploration benefits of anisotropic processing. This volume provides the first comprehensive description of reflection seismic signatures and processing methods in anisotropic media. It identifies the key parameters for time and depth imaging in transversely isotropic media and describes practical methodologies for estimating them from seismic data. Also, it contains a thorough discussion of the important issues of uniqueness and stability of seismic velocity analysis in the presence of anisotropy. The book contains a complete description of anisotropic imaging methods, from the theoretical background to algorithms to implementation issues. Numerous applications to synthetic and field data illustrate the improvements achieved by the anisotropic processing and the possibility of using the estimated anisotropic parameters in lithology discrimination. Focuses on the far reaching exploration benefits of anisotropic processing First comprehensive description of reflection seismic signatures and processing methods in anisotropic media

Over the last few years, anisotropy has become a "hot topic" in seismic exploration and seismology. It is now recognised that geological media deviate more or less from isotropy. This has consequences for acquisition, processing and interpretation of seismic data and also helps determine the cause of anisotropy and adds to our knowledge concerning the structure of the medium at scales beyond the resolution of the seismic method. This volume addresses the theoretical foundations of wave propagation in anisotropic media at an easily accessible level. The treatment is not restricted to exploration seismology. The book commences with fundamental material and covers the description of wave propagation in anisotropic conditions by means of slowness and wave surfaces. It continues to explore the theory of elasticity, the interaction of elasticity and material symmetry and conditions imposed by the stability of the medium. Wave propagation in general anisotropic solids are discussed referring in particular to singular and longitudinal directions. Slowness and wave surfaces in transversely isotropic media and in the planes of symmetry of orthorhombic media is presented and then moves on to wave propagation in orthorhombic media by means of "squared slowness surfaces". The latter part of the book deals with layer-induced anisotropy showing how a particular internal structure of a medium leads to anisotropy and how much of this structure can be recovered by "inversion" of the modelling algorithm. A few fundamental aspects of exploration seismology are also discussed. The final chapter discusses how concepts which were developed by Kelvin, but only recently understood, can be utilised to determine the symmetry class and orientation of an elastic medium.