Periodic and chaotic aseismic and seismic slip sequences on rate-state faults in three dimensions with two loading approaches

So Ozawa, & Robert C. Viesca

Submitted August 30, 2026, SCEC Contribution #15374, 2026 SCEC Annual Meeting Poster #012

Faults can slip in both seismic and aseismic ways. In the framework of rate-state friction, velocity-weakening faults of a comparable size to the nucleation size produce slow slip events (Liu and Rice, 2007; Barbot 2019). This is a classic hypothesis for the mechanism for slow slip events. In this study, we examine the transition from aseismic to seismic slip by increasing the ratio between the fault size and a linear stability dimension in greater detail. We perform 3D simulations of earthquakes and aseismic slip (SEAS) for circular and rectangular velocity-weakening faults. We apply two loading approaches to the fault: uniform backslip and uniform stress rate. The former mimics isolated seismogenic patches in creeping faults, while the latter represents an isolated fault subjected to regional deformation.

Our results show that the transition from stable creep to slow slip events is accurately predicted by linear stability analysis [Viesca and Garagash, in rev., JGR 2026]. The transition from aseismic slip to seismic slip matches well with the prediction from nonlinear stability analysis, with sufficiently low loading rate or low-to-moderate a/b. Near the transition, circular faults produce alternating slow and fast slip events under backslip loading, but only periodic events under stress loading. Rectangular faults with an aspect ratio greater than two produce irregular sequences of slow and fast slip events for both loading approaches. For faults much larger than the nucleation size, many partial ruptures occur under backslip loading but under stress loading. Overall, our results demonstrate the importance of the fault shape and loading approach in controlling the dynamics of aseismic and seismic slip.

Citation
Ozawa, S., & Viesca, R. C. (2026, 08). Periodic and chaotic aseismic and seismic slip sequences on rate-state faults in three dimensions with two loading approaches. Poster Presentation at 2026 SCEC Annual Meeting.

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