Improvement of Reverse Time Migration Image Using a Combination of De-primary and Impedance Matching Methods

When implementing reverse time migration (RTM), reflection energy from velocity discontinuities may produce unwanted artifacts. These artifacts can be removed by applying de-primary RTM algorithm. However, surface-related multiple (SRM) and internal multiple generated during source- and receiver-wavefield extrapolation are correlated into false images even when de-primary RTM is applied. In this paper, we attempt to reduce these unwanted artifacts by using both de-primary and impedance matching simultaneously. Since the impedance matching is valid only for normal incidence, we also apply absorbing boundary condition to free surface to remove SRM. In addition, we eliminate the SRM contained in observed data by using surface-related multiple elimination (SRME) before RTM. We verify our algorithm through the SEG/EAGE salt model example. The numerical examples show that the proposed method works effectively for RTM without velocity smoothing.