Simulations of Microseismicity Associated With Slow Slip Events

Abstract:

Since the discovery of slow slip events along subduction zone interfaces and the densification of regional seismic networks, several associated phenomena have been documented. They include tectonic tremor, very low and low frequency earthquakes, and microseismicity. This study focuses on better understanding the microseismicity, which is most commonly observed at the up-dip or along-strike fringes of a slow slip event. We employ a physics-based earthquake simulator to (1) replicate observed spatial and temporal patterns of slow slip events and microseismicity and (2) explore the conditions necessary to create such potentially related behaviors, and (3) investigate the occurrence of swarm-like microseismicity associated with slow slip events. The earthquake simulator employs a rate-state dependent friction formulation in which the friction is dependent on slip, sliding rate, contact time, and normal stress history. To more realistically model the various modes of fault slip (e.g., earthquake slip versus slow slip) and the interactions between then, we add a velocity threshold to the evolution effect in the friction law. The effective normal stress and cut-off velocity are varied to reproduce the characteristics of observed microseismicity (e.g., stress drop and magnitude). The effective normal stresses are larger than those within the slow slip region, which suggests a relatively lower pore-fluid pressure. Furthermore, the results should illuminate the necessary slip speed required to reproduce the feedback observed between slow slip events and microseismicity. Results from this research will allow for examination into the association of microseismicity and swarm-like activity with large-to-great earthquakes.