ACOUSTIC SCATTERING FROM A FLUID-ELASTIC-SOLID INTERFACE USING THE SMALL SLOPE APPROXIMATION

In this paper the small slope approximation is applied to acoustic sca ttering from a randomly rough fluid-elastic-solid interface. Expressio ns for the zeroth-, first-, and second-order bistatic scattering cross sections are derived. Numerical results are obtained for the zeroth-o rder small slope approximation for Gaussian and modified power law sur face roughness spectra and are compared with those of first-order pert urbation theory and the Kirchhoff approximation. The environmental par ameters used correspond to those of water-granite, water-basalt, or wa ter-sediment interfaces for lossless media. The small slope results sh ow the complex structure associated with elastic wave scattering, incl uding critical angle and Rayleigh angle structure. For the modified po wer law, the small slope results agree with those of Monte Carlo simul ations performed by Berman [J. Acoust. Soc. Am. 89, 623-636 (1991)]. T he study includes a comparison of scattering strengths both with and w ithout the shear wave component. The importance of the shear wave comp onent for a sufficiently rigid solid is illustrated.