Prestack Depth Migration Using Seismic Virtual Source Gathers

Abstract

Prestack depth migration is used to image for complex geological structure. In this case, the surface reflection data are used as an input data in general. However, the surface reflection data have some problems in imaging the subsalt and the salt flank due to the complex wavefields and multiples which come from overburden. To overcome the defect of the surface reflection data, we used the virtual source in terms of seismic interferometry to image the subsurface. Inhomogeneous velocity models were developed and virtual source gathers were generated ocean bottom seismic numerical modelling. Cross-correlation gathers were generated by the crosscorrelation between the reference trace and others. The virtual source gathers were made by the integration at the stationary phase interval. Numerical test showed that the virtual source gathers integrated at the stationary interval are superior to that of all sources. To verify the possibility of subsurface imaging, prestack depth migration was applied for the virtual source gathers. This prestack depth migrated section re-produced the velocity model below receivers.. Especially artificial interface by multiples were suppressed without any further data processing. The results of imaging obtained from inhomogeneous velocity model below receivers also showed that the artificial geological interfaces were significantly reduced comparing to the homogeneous velocity models case.