Abstract

Anisotropy (e.g., directional dependence of velocity at a fixed spatial location in a medium) plays a very important role in seismic imaging. It is very difficult to know the presence of anisotropy in the subsurface geological formations only from P-wave seismic data and special analysis is required for this. The presence of anisotropy causes two major distortions of moveout in Pwave seismic reflection data. First, in contrast to isotropic media, normal moveout (NMO) velocity differs from the vertical velocity; and the second is substantial increase of deviations in hyperbolic moveout in an anisotropic layer. Hence, with the help of conventional velocity analysis based on shortspread moveout (stacking) velocities does not provide enough information to determine the true vertical velocity in a transversely isotropic media with vertical symmetry axis (VTI media).