Zero-offset P-S energy in horizontally layered media

The existence of non-zero reflectivity for zero-offset PS waves in horizontally layered media is discussed. Field measurements have suggested the occurrence of this phenomenon. We show that, in some cases, if anisotropy is considered in the problem, this reflectivity can be predicted. By using an approximated formulation to determine the coefficient of reflection in arbitrarily anisotropic media, it is clear that, for some elastic arrangements of the subsurface, reflected energy is associated with the converted wave resulting from normal P-wave incidence.