Pulse-Like Partial Ruptures and High-Frequency Radiation at Creeping-Locked Transition during Megathrust Earthquakes

Sylvain G. Michel, Jean-Philippe Avouac, Nadia Lapusta, & Junle Jiang

Submitted August 15, 2017, SCEC Contribution #7863, 2017 SCEC Annual Meeting Poster #183

Megathrust earthquakes tend to be confined to fault areas locked in the interseismic period and often rupture them only partially. For example, during the 2015 M7.8 Gorkha earthquake, Nepal, a slip pulse propagating along strike unzipped the bottom edge of the locked portion of the Main Himalayan Thrust (MHT). The lower edge of the rupture produced dominant high-frequency (>1 Hz) radiation of seismic waves. We show that similar partial ruptures occur spontaneously in a simple dynamic model of earthquake sequences. The fault is governed by standard laboratory-based rate-and-state friction with the ageing law and contains one homogenous velocity-weakening (VW) region embedded in a velocity-strengthening (VS) area. Our simulations incorporate inertial wave-mediated effects during seismic ruptures (they are thus fully dynamic) and account for all phases of the seismic cycle in a self-consistent way. Earthquakes nucleate at the edge of the VW area and partial ruptures tend to stay confined within this zone of higher prestress, producing pulse-like ruptures that propagate along strike. The amplitude of the high-frequency sources is enhanced in the zone of higher, heterogeneous stress at the edge of the VW area.

Key Words
Partial Ruptures, Gorkha earthquake, Pulse, High-Frequency Radiation, Megathrust Earthquakes

Citation
Michel, S. G., Avouac, J., Lapusta, N., & Jiang, J. (2017, 08). Pulse-Like Partial Ruptures and High-Frequency Radiation at Creeping-Locked Transition during Megathrust Earthquakes. Poster Presentation at 2017 SCEC Annual Meeting.


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