3‐D converted‐wave processing in the presence of large S‐wave splitting and statics

Abstract

When shear‐wave splitting in the overburden becomes large enough for the time delay between fast and slow wavefields to be greater than the dominant period of the data, then it becomes difficult to make progress in processing converted‐wave data. The radial component contains large S‐wave statics as well as large time delays and waveform contamination due to S‐wave splitting. It becomes impossible to resolve the large S‐wave statics with radial common‐receiver stacks (Cary and Eaton, 1992) because of the large azimuthal variations due to splitting. A method is presented here that enables birefringence in the overburden to be analysed and removed from the data before S‐wave statics are resolved. This method involves the azimuthal analysis of the radial component of prestack NMO‐corrected receiver gathers. The fact that S‐wave statics are constant within each receiver gather allows the separation of the statics from the splitting effects. Receiver gathers are the ideal type of gather for analysing birefringence in the overburden since they collect the transmission effects of the shear‐wave splitting that are common below each receiver.