A High-resolution Vector-imaging Condition for Elastic Reverse-time Migration

We introduce a new vector-imaging condition for elastic reverse-time migration to produce high-resolution migration images. This new imaging condition is developed by the use of polarization vectors of wave fields along with the conventional imaging condition. The conventional imaging condition as that used for scalar-wave migration, is established on the principle that incident and reflected waves coincide in phase at a reflection point. Our vector-imaging condition also makes use of directional coincidence of the forward and backward propagating elastic waves. The polarization vectors of elastic wave fields are obtained by spatial derivatives of the corresponding waves in the frequency domain. We demonstrate using synthetic examples that the use of polarization vectors in the imaging condition significantly improves migration images. Elastic-wave reverse-time migration with the new vector-imaging condition will enable us to reliably image complex subsurface structures, particularly for true-amplitude migration.