Synthetic vertical seismic profiles in elastic media

Numerical simulations of vertical seismic profiles in flat-layered elastic media using the discrete wavenumber method are presented. The effect of source-borehole sep- aration on recorded wave types and amplitudes is studied. For nonzero source offsets, transverse and converted waves become very important and can be more energetic than the direct compressional arrivals. A systematic comparison of results from acoustic and elastic simulationsshows that the acoustic approximation is quite valid for a zero source offset but becomes inadequate when the configuration of the source and vertical geophone array is two-dimensional. Recording of both pressure and displacement allows a simple separation of transverse and compressional arrivals as long as the effect of the borehole on the incoming waves can be neglected.