Wave equation depth migration using complex Padé approximation

Abstract

We propose a new method of depth migration based on a constant density variable velocity wave equation in the space-frequency domain. A complex Padé approximation of the wave equation evolution operator is used for wavefield extrapolation. This method mitigates the inaccuracies and instabilities due to evanescent waves and produces images with fewer numerical artifacts than those obtained with a real Padé approximation of the exponential operator, mainly in media with strong velocity variations. Tests on zero-offset data from the SEG/EAGE salt model and the 2D Marmousi prestack dataset show that the proposed migration method can handle strong lateral variations and also has a good steep dip response. We compare the results of the proposed method with those obtained using split-step Fourier (SSF), phase shift plus interpolation (PSPI) and Fourier finite-difference (FFD) methods.