Converted PS-wave imaging based on offset vector tiles

Abstract

Stacking using offset vector tiles (OVTs) is a technique used to simultaneously retain the offset and azimuth information in a wide-azimuth seismic survey by building minimal data sets of underground homogeneous illumination. Currently, derived from the assumption that reflection points and common midpoints are in the same lateral location because the raypath is symmetric, PP-wave OVT processing has been widely applied to seismic imaging and offset and/or azimuth analysis. However, it is difficult to directly apply the PP-wave OVT gathering method to the PS wave because the PS-wave raypath is asymmetric and the conversion point varies with depth. To solve this problem, we have developed an improved PS-wave OVT imaging technique based on the precise conversion point calculation and the equivalent converted-wave hypothesis, in which the PS-wave OVT gather with homogeneous illumination can be obtained in a manner similar to the PP wave. Moreover, to further improve the imaging quality, an azimuthal anisotropic normal moveout is applied to correct the traveltime difference. With tests of synthetic and field data, it can be concluded that our method represents a new and feasible solution for PS-wave OVT gathering.