A review of wave motion in anisotropic and cracked elastic-media

Recent developments in the theory and calculation of wave propagation in anisotropic media have been published in the geophysical literature and refer specifically to seismological applications. Anisotropic phenomena are comparatively common, and it is the intention of this review to present these developments to a wider audience. Few of the results are new, but the opportunity is taken to tidy up a few loose ends, and present consistent theoretical formulations for the numerical solution of a number of propagation problems. Such numerical experiments have played a large part in our increasing understanding of wave motion in anisotropic media. It now appears that the solution of most problems in anisotropic propagation can be formulated, if the corresponding solution exists for isotropic propagation, and may be solved at the cost of considerably more numerical computation.

There are two significant results from these developments: the recognition of the importance of body- and surface-wave polarizations in diagnosing and estimating anisotropy; and the recognition that many two-phase materials, particularly cracked solids, can be modelled by anisotropic elastic-constants. This last result opens up a new class of materials to wave-motion analysis, and has applications in a variety of different fields.