Multiwave Gaussian beam prestack depth migration of exploration‐scale seismic data with complex near‐surface effects

Abstract

ABSTRACTThe direct prestack depth migration methods of nonplanar data provide effective ways to address the complex near‐surface problem. Based on the study of local slant stacks considering the elevation and dip angle information of an irregular surface, an alternative method for multiwave Gaussian beam prestack depth migration of exploration‐scale seismic data with complex near‐surface effects is presented here. We first derive the downward‐continued wavefield for an irregular surface in terms of Gaussian beams, where we directly decompose the seismic records within a Gaussian window into a local plane‐wave component. The PP‐ and PS‐wave Gaussian beam prestack depth migration methods under complex near‐surface conditions are then presented, after the wavefield separation is performed with an affine coordinate‐system transform. Tests with numerical examples demonstrate the accuracy and effectiveness of the method.