Seismic Waves in Laterally Inhomogeneous Media

A new perturbation technique is presented for the approximate solution of problems involving slight lateral inhomogeneities, or moderate inhomogeneities of small lateral extent, in elastic media. The method, based on an integral equation formulation and Born-type expansion in the wavenumber domain, is an extension of the usual matrix methods for multilayered elastic media. It is thus particularly suitable for problems concerning inclusions in multilayered half spaces. As an example of this method calculations are made of the scattering effects produced by near-surface inclusions in simple half-space models. It is found that at low frequencies forward and backward scattering into surface waves are of comparable importance, but as the frequency of the incident waves increases the forward scattering tends to dominate.