Amplitude characteristics of wave propagation and reverse time migration

Abstract

Prestack Reverse time migration (RTM) algorithm for depth imaging has now become feasible due to advances in high performance computing and clever programming techniques. RTM makes use of full acoustic two‐way wave propagation algorithm for both forward and reverse time extrapolation. Amplitude preservation is based upon the assumption that acoustic wave equation approximates the wave propagation in real elastic earth. In this paper, we first compare the amplitude characteristics of both the acoustic and elastic wave propagation by looking at the reflection coefficients for a simple flat layered model. Then the input gathers generated by both acoustic and elastic forward modeling algorithm are migrated with RTM method. The amplitude behavior of the RTM algorithm is studied by looking at the amplitudes of migrated gathers. The study shows that even for a simple flat layered earth model the assumption of acoustic wave propagation in RTM may not be valid. Therefore special care must be taken while interpreting amplitude information on migrated gathers.