A hybrid elastic one-way propagator for strong-contrast media and its application to subsalt imaging

Abstract

For elastic-wave propagation in strong-contrast media, we developed the theory and method of a new one-way operator, which can overcome the weak perturbation assumption of a traditional elastic thin-slab propagator. In the framework of the new propagator, the elastic model is separated into several domains along the strong-contrast boundaries. Different background velocities are chosen for different domains so that each domain can be considered as a weakly heterogeneous media with a sharp boundary. The new propagator adopts a hybrid approach to extrapolate the wavefields in each domain: a traditional thin-slab propagator for weak heterogeneities combined with a reflection/transmission operator for wave exchanging at the sharp boundary. It inherits the dual domain (wavenumber-space domain), depth-marching implementation of an elastic thin-slab propagator. The boundary is discretized into a collection of boundary segments based on the marching depth, and the reflection/transmission operators are estimated locally at the boundary segment by making a tangent plane approximation. By neglecting the reverberation between the boundary segments, the reflected/transmitted wave from the boundary can be gradually incorporated into wave propagation in a one-way fashion. We validated the accuracy and efficiency of the hybrid propagator by showing numerical simulation results on two simple salt models. Finally, we applied the hybrid propagator to subsalt imaging using a synthetic data set generated from a 2D subsalt model.