Reverse Time Migration Based on the Pseudo-Space-Domain First-Order Velocity-Stress Acoustic Wave Equation

Xiaobo Zhang,Jun Tan,Peng Song,Xiutian Wang,Chuang Xie,Baohua Liu

doi:10.3389/feart.2021.690513

Abstract

Reverse time migration (RTM) is an ideal seismic imaging method for complex structures. However, in conventional RTM based on rectangular mesh discretization, the medium interfaces are usually distorted. Besides, reflected waves generated by the two-way wave equation can cause artifacts during imaging. To overcome these problems, a high-order finite-difference (FD) scheme and stability condition for the pseudo-space-domain first-order velocity-stress acoustic wave equation were derived, and based on the staggered-grid FD scheme, the RTM of the pseudo-space-domain acoustic wave equation was implemented. Model experiments showed that the proposed RTM of the pseudo-space-domain acoustic wave equation could systematically avoid the interface distortion problem when the velocity interfaces were considered to compute the pseudo-space-domain intervals. Moreover, this method could effectively suppress the false scattering of dipping interfaces and reflections during wavefield extrapolation, thereby reducing migration artifacts on the profile and significantly improving the quality of migration imaging.

Highlights

Based on the theory of the two-way wave equation, the reverse time migration (RTM) algorithm was conceived in the early 1980s (McMechan, 1983; Whitmore, 1983)
In the implementation of FD numerical simulations based on the pseudo-space-domain acoustic wave equation, as well as to improve the accuracy of the simulation and suppress the impact of numerical dispersion, we need to improve the accuracy of the differences
In this study, we implement an effective boundary storage strategy (Clapp, 2008; Wang et al, 2012) based on perfectly matched layer (PML) boundary conditions in the pseudo-space-domain. This entails storing the wavefield value of the N-layer grid point that is adjacent to the central wavefield on each PML boundary during the forward time source wavefield extrapolation, as well as the central wavefield value at the last moment

Summary

INTRODUCTION

Based on the theory of the two-way wave equation, the reverse time migration (RTM) algorithm was conceived in the early 1980s (McMechan, 1983; Whitmore, 1983). In this study, we implement an effective boundary storage strategy (Clapp, 2008; Wang et al, 2012) based on PML boundary conditions in the pseudo-space-domain This entails storing the wavefield value of the N-layer grid point (the FD order is 2Nth order) that is adjacent to the central wavefield on each PML boundary during the forward time source wavefield extrapolation, as well as the central wavefield value at the last moment. Based on the model of 10 m grid interval as shown, the FD algorithm for the conventional and pseudospace-domain acoustic wave equations is used for RTM with second-order accuracy in time and sixteenth-order accuracy in both space and pseudo-space. This demonstrates that the imaging quality of RTM by using the pseudo-space-domain acoustic wave equation is better than that obtained by using a conventional acoustic wave equation

CONCLUSION AND DISCUSSION

Findings

DATA AVAILABILITY STATEMENT