Processing of seismic data in the presence of anisotropy

Abstract

Processing techniques for extracting the polarization directions of the fast, and slower split shear waves, together with their traveltime splitting from vector wavefield data, form the basis of prospective procedures for imaging details of the internal structure of subsurface rocks. A recently developed technique involving the independent rotation of the source polarization direction, and geophone axes, provides an effective processing tool for extracting the effects of anisotropy from shear‐wave data. It is theoretically capable of handling nonorthogonal polarization directions of split shear waves. It is further developed, and its performance examined using vertical seismic profiling (VSP) shear‐wave datasets for different anisotropic earth models, and computed using full‐wave modeling. The procedure works well for shear waves propagating through an earth model with a uniform crack strike with depth, but produces inaccurate estimates of polarization and time‐delay when the crack strike varies abruptly with depth. It is unlikely that other techniques could do better under these circumstances, as the problems arise due to the complexities introduced by multiple shear‐wave splitting.