Acoustic Prestack Reverse Time Migration Using the Adaptive High‐Order Finite‐Difference Method in the Time‐Space Domain

Abstract

Abstract:At present, prestack reverse time migration (RTM) is the most accurate method for seismic imaging in theory. One of its key steps is wavefield extrapolation. The essence of wavefield extrapolation is to solve the wave equation. Thus solving the wave equation fast yet accurately is very important. In this paper, we use a time‐space domain dispersion‐relation‐based finite‐difference (FD) method to solve the acoustic wave equation, then analyze the dispersion and stability of the numerical solution, perform the numerical modeling, and compare the results with the conventional FD method. The results of analysis and numerical modeling demonstrate the time‐space domain FD method has better accuracy and stability than the conventional method under the same discretization. We adopt the time‐space domain high‐order FD method to solve the acoustic wave equation in the process of wavefield extrapolation, then use the normalized cross‐correlation imaging condition to obtain imaging in RTM. The results of synthetic data processing show that the imaging accuracy has enhanced. Meanwhile, in the process of wavefield extrapolation, we adopt adaptive variable‐length spatial operators to compute spatial derivatives and thus to decrease computing cost significantly without reducing the accuracy of numerical modeling and imaging.