Prestack depth migration method using the time-space Gaussian beam

Abstract

Summary We adopt the time-space Gaussian beam for seismic data prestack depth migration in this abstract. This method belongs to the category of ray-based beam methods. It decomposes source wavelet into a set of Gaussian functions and propagates these Gaussian functions along appropriate central ray paths to construct the forward seismic wavefield, which is comparable to that produced by finite difference method. For the backward propagation of recorded wave-filed, the Kirchhoff integral equation is used, in which the Green function is represented approximately by time-space Gaussian beam summation. The subsurface image is obtained by calculating the coherence between the direct and back-propagated wave-fields. Unlike Kirchhoff migration and conventional Gaussian beam migration, we perform the ray tracing from subsurface imaging points to the receiver surface to compute the backward Green function, which adhering strictly to the mathematical basis of the Gaussian beam summation method. In addition, our method is carried out in the time-space domain, which could reveal the local time features of seismic wave-field that can be used to reduce the coherence noise of depth images. Two typical numerical examples confirm the validity and adaptibility of the time-space Gaussian beam migration.