Solutions to numerical dispersion error of time FD in RTM

Abstract

Summary Finite difference (FD) methods used in reverse time migration (RTM) often have imbalanced accuracies in approximating time and space derivatives. Coarse spacing combined with low order FD in the time domain induces numerical dispersion error, which results in phase rotation and depth errors in RTM images. We describe two different methods to resolve the time numerical dispersion issue: 1) a wave propagation algorithm called Explicit Time Evolution (ETE), which employs optimized stencils and coefficients to cost-effectively achieve improved accuracy, and 2) a time varying phase shift (TVPS) method applied to the input seismic traces before RTM to compensate for the dispersion from time FD.