abstract

Finite difference techniques are applied to study the response of a sedimentary basin in an isotropic elastic half-space to vertically incident compressional and shear sources. The sedimentary rock of the basin is modeled as a transversely isotropic material. Improved finite difference approximations to the boundary conditions are developed.

Of primary interest is the formation of Rayleigh waves over the flank of the basin. Displacement time series at points on the free surface and Rayleigh orbits are plotted. Three-dimensional spectral amplitude graphs of the entire time series up to a period of temporary quiescence are presented. The Rayleigh wave is the dominant scattered phase for the basin geometry considered, having 20 to 30 per cent of the source displacement amplitude at the free surface in a basin with 26° flanks, 0.7-km depth, 6-km width, over a half-space whose acoustic impedance contrast with the basin was two. The effect of varying the degree of compressional anisotropy in the basin on the amplitudes of refracted and scattered phases of engineering interest was minimal.

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