Unified Approach for Elastic and Acoustic Wave Propagation

The main objective of this study is to develop and implement numerically a unified approach for simulating seismic wave propagation in elastic and acoustic media. We resort to a mixed finite element formulation as the solution procedure in order to overcome the limitations of sole displacement- or velocity-based formulations, which result in spurious modes and inaccurate results for large P-wave velocity to S-wave velocity ratios. We examine the transition of solid to fluid behavior via numerical examples using Hercules, our octree-based finite element code, developed originally for wave propagation modeling on purely anelastic media. We also examine in detail the influence of the type of boundary conditions on the ground motion, and explore the applicability of the unified approach to the modeling of the inception of tsunamis.