Reflection coefficients of spherical PS waves considering non-geometric waves at a viscoelastic interface

The plane wave reflection and transmittion (R/T) coefficients which are of critical importance in the routine Amplitude Versus Offset (AVO) analysis are based on the geometrical seismic approximation (in accordance with Snell's law) which becomes inadequate in describing reflected wavefields at nearand post-critical incidence angles. The spherical wave R/T coefficients play an important role in wide angle AVO analysis, seismic inversion and cross-borehole surveys in which non-geometric waves are created by the downhole sources close to the interfaces. Furthermore, the existence of non-geometric PS waves, e.g. leaking waves, pseudo-spherical S waves (S∗) must affecte spherical wave reflection coefficients (SWRC) values and need to be investigated, especially the SWRC of converted PS waves because of their speciall features. In this abstract, the equations for SWRC and the particle displacements are introcued or derived for the viscoelastic materials. For the numerical examples, the viscoelastic materials are assumed to be expressed with the constant-Q model. The numerical results show that unlike plane waves, SWRC of converted PS-waves are not zero at vertical or near- vertical incidence and may be drastically influenced by the existence of longitudinal PS-waves which are confirmed by the waveform calculations for the converted PS-waves.