WAVE-EQUATION-BASED DECOMPOSITION AND IMAGING FOR MULTICOMPONENT SEISMIC DATA

Compared with conventional single-component seismic data, multicompone nt data in which both compressional (P) and shear (S) waves may exist, contain much additional information about the elastic parameters of t he subsurface. Decomposition of multicomponent data into primary P- an d S-wave responses and imaging of the decomposed wavefields are the tw o main procedures for multicomponent seismic data processing. Based on the imaged P-P and P-SV configuration, the rock- and pore parameters may be estimated. In this work, we first derive the decomposition form ula from the elastic wave equation to divide the common shot gathers ( CSP) of the displacement vector into scalar upgoing P- and SV-waves. A ccording to the characteristics of the formula, the pure P-wave can be decomposed by revising the vertical component with the correction of the horizontal component, which can enhance the P-wave, but eliminate the SV-wave in the vertical component. Similarly, the pure SV-wave can be decomposed by revising the horizontal component with the use of th e vertical component. The decomposition process requires the knowledge of the elastic parameters at the surface. Then we can reconstruct the subsurface image by performing downward extrapolation of the separate d scalar upgoing P- and SV-wavefields. The P-P and P-SV subsurface can be imaged independently with the correlation of forward extrapolation to each depth step from the source for downgoing waves and inverse ex trapolation for the P- or SV-waves, based on the acoustic one-way wave equation for upgoing waves propagating with the respective P- or SV-w ave velocity. The screen propagators can be used effectively in this c ase. Results from synthetic data of one two-component shot records sho w that the P- and SV-waves are decomposed completely and that the subs urface image for P-P waves is consistent with P-SV waves.