Pure P- and S-wave elastic reverse time migration with adjoint state method imaging condition

Abstract

We implemented an elastic reverse time migration based on a coupled system of pure P-and S-wave particle velocities. The system utilizes finite difference wavefields for P-and S-wave particle velocity in vertical and horizontal directions (vpx , vpz , vsx and vsz), and for 2-D displacement divergence and curl (A and B). In contrast with the usual elastic imaging conditions that cross-correlates vertical displacements to obtain the P-wave image and vertical and horizontal displacements to obtain the converted wave image, we devised P-and S-wave imaging conditions using the adjoint state method. The resulting imaging conditions cross-correlate spatial derivatives of A and B wavefields with P-and Swave displacements. The proposed migration shows a better reflector definition and more balanced amplitudes than the usual vertical and horizontal particle displacement cross-correlations.