ZRTM with depth extrapolation in space and wavenumber dual-domain

Abstract

Summary Wavefield extrapolation (wavefield continuation) plays a significant role both in modeling and migration. According to the types of the wave equation, it can be divided into one-way method and two-way method. One-way method is based on the split of the full wave equation, which therefore allows the wave propagates only downward or upward. This method has been widely investigated and used due to its efficiency. However, the one-way approximation for wave equation may lead to unsatisfactory images for the structures of steep dips or strong lateral velocity variations. Two-way method is comparingly accurate even in complex geological settings but requires more computational costs. This paper presents a post-stack depth migration method, zRTM, based on a new wave-field extrapolation scheme. The new extrapolation scheme is directly derived from two-way wave equation without any approximation and hence can preserve all the useful information of wave propagation. Additionally, its implementation shares the similar structure with one-way phase shift method, thereby bringing the computational efficiency. We illustrate the effectiveness of this new method by impulse responses in different velocity models. SEG-EAGE salt model is also used to show the quality of the new extrapolation scheme in post-stack depth migration.