A new decoupling and elastic propagator for efficient elastic reverse time migration

Methods to decompose the elastic wavefield into compressional wave (P-wave) and shear wave (S-wave) components in heterogeneous media without wavefield distortions or energy leakage are the key issues in elastic imaging and inversion. We have introduced a decoupled P- and S-wave propagator to form an efficient elastic reverse time migration (RTM) framework, without assuming homogeneous Lamé parameters. Also, no wave-mode conversions occur using the proposed propagator in the presence of strong heterogeneities, which avoids the potential imaging artifacts caused by wave-mode conversions in the receiver-side backward extrapolation. In the proposed elastic RTM framework, the source-side forward wavefield is simulated with a P-wave propagator. The receiver-side wavefield is back extrapolated with the proposed propagator, using the recorded multicomponent seismic data as input. Compared to the conventional elastic RTM, the proposed framework reduces the computational complexity while preserving the imaging accuracy. We have determined its accuracy and efficiency using two synthetic examples. © 2020 Society of Exploration Geophysicists.