A Novel P/S Decoupling Scheme With an Exact Riemann Solver on Coupling Fluid–Solid Media

Elastic wavefield separation has attracted much attention in the field of geophysics, but the focus is mainly on a single solid medium, which is hardly used in the coupled medium. We propose an effective discontinuous Galerkin (DG) approach with the exact Riemann solver for modeling decoupling P- and S- wavefield propagation in coupling solid-fluid media. We apply the selective strong attenuation to P- or S-waves by the viscoelastic theory while keeping the other wave mode. The viscoelastic wave equation is first cast into the decoupling wave equation. Following, we derive a novel exact Riemann solver that can accurately couple with the fluid and the decoupling elastic media. Finally, we use the DG method to solve P/S decoupling wave equations in triangular and tetrahedral meshes. The original wavefield is accurately decomposed into P and S wavefields, whose phases and amplitudes are consistent with those of the elastic data. Several numerical experiments are used to demonstrate the accuracy and capacity of our developed P/S-separated approach.