Flank-preserving deprimary reverse time migration

Deprimary reverse time migration (RTM) is a newly proposed technology aiming at removing false structures in images computed by RTM. However, a side effect of this new technology is an inability to image steeply dipping structures. We first introduce how to obtain a composite wavefield, including a complete downgoing wavefield and a partial upgoing wavefield, using the combination of an f-k filter and a spatial-wavenumber filter. We next thoroughly analyze the root cause leading to this side effect in the deprimary RTM technology. By using a modified imaging condition accommodating a composite wavefield, we propose a novel flank-preserving deprimary RTM method to maintain the capability of removing false structures and preserve steeply dipping subsurface structures in the final image. We demonstrate the success of this new technology via several examples. Furthermore, we study different perspectives in depth to show that flank-preserving deprimary RTM is a trade-off solution between RTM and deprimary RTM.