Finite Element Simulation of Earthquakes with Coupling Tsunamis in Large Domains — A Case Study of the 2011 Tohoku-Oki Earthquake and Tsunami

Abstract:

Seaquakes and tsunamis are usually coupled in nature. This is especially evident around the subduction zones where most of the top ten strongest earthquakes have been recorded in the last century.
Addressing the coupled nature of the two phenomena requires concurrent simulations. Accordingly, this study deals with the simulation of strongly-coupled subduction zone earthquakes, with a focus on the generation of tsunami waves.
We present an application to the 2011 Tohoku-Oki earthquake and tsunami employing a multi-system finite element method for the elastoacoustic problem. In the past, we have reported on the simulation capabilities of Hercules, our finite element tool, for earthquake scenarios such as ShakeOut and Chino-Hills using ideal anelastic material models with kinematic faulting. With the latest improvements we have introduced into Hercules, we can now incorporate oceans and the attendant gravity waves into our three-dimensional simulations.
We examine the relationship between the fault rupture, the generation of the tsunami, and the ocean’s effects on the propagation of seismic waves through the solid and acoustic media. Additionally, we clarify the validity of common assumptions made for the tsunami generation mechanism with classical tsunami simulation methods. While our focus is on the physical interpretation of the results and its comparison with observations, we also report on the current understanding of the geologic structure of the Japan Trench, computing resources, and the numerical method.