Explore the mechanism of tsunami earthquake generation using earthquake cycle simulation

Qingjun Meng, Benchun Duan, & Bin Luo

Published August 4, 2021, SCEC Contribution #11160, 2021 SCEC Annual Meeting Poster #130

Since 1900, nine Mw>=7.5 historical tsunami earthquakes have occurred along shallow subduction zones and generated larger tsunami hazards than their Ms magnitudes implied. Previous observations found that tsunami earthquakes propagate at slower speed with longer duration, lower high-frequency radiation and larger discrepancy between Mw and Ms than regular megathrust earthquakes. In this study, we use a recently developed dynamic earthquake simulator, which incorporates a rate and state-dependent friction aging law and captures both quasi-static and dynamic processes, to explore the tsunami earthquake generation from a physics-based modeling point of view. We build a 3D shallow-dipping subduction zone model in which strong velocity weakening, unstable patches (asperities) are distributed within a conditionally stable subduction interface at shallow depth. Simulation results show that earthquakes can only nucleate on these asperities and their rupture speeds are largely slowed down after propagating into the surrounding conditionally stable zone, because the conditionally stable zone is less velocity weakening. The earthquakes nucleate on the asperity with high normal stress (HNS) could cascadingly rupture the nearby asperities with low normal stress (LNS) and generate high on-fault slip and seafloor displacement. However, earthquakes nucleate on the LNS asperity are difficult to rupture the HNS asperity and generate low on-fault slip and seafloor displacement. The degree of velocity-weakening in the conditionally stable zone, which influences the earthquake rupture speed and recurrence interval, is crucial for tsunami earthquake generation and contributes to the earthquake characteristics, such long duration and depletion of high-frequency. In addition, the layout features of various asperities also strongly affect the final rupture pattern, generating diverse characteristics of simulated tsunami earthquakes. These modeling results can shed lights onto observations from historical tsunami earthquakes, including the 1994 and 2006 Java tsunami earthquakes and 2010 Mentawai tsunami earthquake.

Citation
Meng, Q., Duan, B., & Luo, B. (2021, 08). Explore the mechanism of tsunami earthquake generation using earthquake cycle simulation. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)