Angle domain common imaging point gathers during Kirchhoff PSTM

Summary In this paper we present the improved algorithm for angle domain common imaging point gathers during pre-stack Kirchhoff time migration. The algorithm can calculate relatively true incident angle under three-dimensional circumstance, while the traditional ray-parameter method could not handle the incident angle for the dipping events. Compared with straight-ray Kirchhhoff angle domain gathers method proposed in recent years, our method is able to extract wide-angle. Increased angular illumination is beneficial for AVA inversion. The results of synthetic model data have verified that : for V(z) (layered) media, the traveltime calculation adopt bending ray, which is much more accurate than straight ray for large angle. Using the method, the wide angles of angle domain common imaging point gather are flat. For laterally varied velocity medium, we apply the asymmetry ray to calculate the travel time. The asymmetry travel time method is able to deal with the media with laterally varied velocity, while the conventional Kirchhoff migration fails to solve the problem.