Separation of P waves and S waves in the VSP wavefield on the basis of a forward modelling technique

Abstract

Separation of P waves and S waves in the VSP wavefield is proposed on the basis of a synthetic forward modelling technique. The weak wavefield masked by dominant wave trains can be extracted with this method. The decomposed wavefield is expressed in frequency-depth (f-z) domain as a linear combination of up to third order differential of traces, which is approximated by trace differences in the practical separation process. In general, five traces with single-component data are required in this process, but the same process is implemented with only three traces in the acoustic case. Two-trace extrapolation is applied to each edge of data gather in order to enhance the accuracy of trace difference. Since the formula is developed in f-z domain, the influence of anelasticity is taken into account with simplicity and the calculation is fast enough with the benefit of the fast Fourier transform (FFT).