Leaky Rayleigh wave scattering from elastic media with random microstructures

Scattering of leaky Rayleigh waves from a flat fluid-solid interface is studied. The fluid half-space is taken to be ideal and homogeneous while the solid half-space has randomly inhomogeneous anisotropic elastic constants due to the microstructure of the material. For plane waves incident from the fluid onto the interface at the critical Rayleigh angle the singly scattered incoherent field is obtained by utilizing a first Born approximation. When the solid is a crystal aggregate and when the correlation function is of exponential form, the mean-square scattered signal level is found to be inversely proportional to the dimensionless frequency in the geometrical (high-frequency) limit but proportional to the third power of frequency in the Rayleigh (low-frequency) limit. Numerical results are given for water- aluminum (cubic polycrystals) interface scattering.