Shear waves from 3-D–9-C seismic reflection data

Nine-component (9-C) 3-D seismic reflection data are acquired using orthogonal shear-wave sources and orthogonal horizontal geophones. Shear-wave sources are oriented inline and crossline (SI and SX) to the receiver lines, as are the horizontal geophones (RI and RX). Four shear-wave data sets result (SI,RI; SI,RX; SX,RI,SX,RX). These inline-crossline coordinates are referred to as field coordinates. A main interpretation emphasis for these data has been to infer the presence of vertical cracks using shear-wave birefringence. Nonzero crossterms (SI,RX; SX,RI) have been used as an indicator that shear-wave birefringence (splitting) is present.