Unraveling scaling properties of slow slip events in 3D simulations of fault slip

Luca Dal Zilio, Nadia Lapusta, & Jean-Philippe Avouac

Published August 14, 2020, SCEC Contribution #10607, 2020 SCEC Annual Meeting Poster #167 (PDF)

Large megathrust faults produce a wide spectrum of slip modes, ranging from earthquakes to slow-slip events (SSEs). SSEs appear to have slip mechanisms similar to those of regular (fast) earthquakes and are often located in neighboring regions of the seismogenic zone. However, whether SSEs and regular earthquakes arise from similar failure mechanisms, and how different slip behaviors are separated in space and time, are still a matter of debate. We examine the scaling properties of SSEs using 3D dynamic simulations of frictional sliding in fault model of a velocity-weakening fault strip surrounded by velocity-strengthening areas on a rate-and-state fault with inelastic dilatancy and fluid overpressure. Simulated SSEs follow the Gutenberg-Richter law and obey a cubic moment-duration scaling law — similar to that of fast (regular) earthquakes — as observed in Cascadia. In contrast to conventional and widely used assumptions of magnitude-invariant rupture velocities and stress drops, both simulated and natural SSEs have rupture velocities and stress drops that increase with event magnitudes. The success of our model in reproducing a realistic sequence of SSEs provides an excellent match to a number of observations collected along the Cascadia megathrust and indicates that rate-and-state friction combined with pore fluids effects is a plausible physical mechanism for SSEs.

Key Words
slow-slip events; scaling; cascadia; megathrust; subduction zones; rate-and-state friction; dilatancy;

Citation
Dal Zilio, L., Lapusta, N., & Avouac, J. (2020, 08). Unraveling scaling properties of slow slip events in 3D simulations of fault slip. Poster Presentation at 2020 SCEC Annual Meeting.

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