Elastic-wave reverse-time migration with a wavefield-separation imaging condition

Elastic-wave reverse-time migration (ERTM) is the most promising tool for true-amplitude and high-resolution migration in complex regions. However, conventional imaging conditions used in ERTM have two major drawbacks that result in severe image artifacts. One is caused by the conventional imaging of the full waves and another is caused by the polarizations between P and S waves. We introduce a new ERTM scheme to eliminate these drawbacks. It is based on the separation of waveflelds with respect to a given direction. The separation is achieved after the elastic waveflelds are downward continued into a target imaging region. The new ERTM does not make any assumption on elastic wave propagation, neither does it utilize a post-processing filtering on migration images. The separation of the wavefields is carried out using an approach for separation of VSP upgoing/downgoing wavefields. Synthetic imaging examples demonstrate that our ERTM scheme can effectively eliminate image artifacts of conventional reverse-time migration methods.