Role of Accretionary Wedge in the Dynamic Rupture of Tsunami Earthquakes

Abstract

Tsunami earthquakes occur in the shallow parts of subduction megathrust interfaces, which are often in contact with the accretionary wedge. Here, by conducting dynamic rupture simulations, we investigate how an accretionary wedge affects the rupture process of tsunami earthquakes and the resulting ground motions. We constructed a dynamic source model of the 2010 Mentawai tsunami earthquake (Mw 7.8), constrained by the slip distribution obtained by a source inversion analysis. The model reproduces the basic observed features of the event, including its recorded ground motions and its inferred slow rupture speed. The simulation results also show that seismic wave energy is efficiently trapped inside the accretionary wedge, which contributes to our understandings of the observation that tsunami earthquakes produce weaker ground motions than regular earthquakes of the same magnitude.