| The recent discovery of slow slip events (SSEs) in subduction zones has resulted in a variety of new observations that are modeled using the new, physics-based, computationally efficient, earthquake simulation code, RSQSim. RSQSim fully incorporates 3D elastic stress interactions and employs rate- and-state constitutive properties for the sliding strength of faults. RSQSim is capable of generating 100,000s of slip events, which is ideal to understand the long-term characteristics of SSEs and their interactions with adjacent sections of the megathrust. For the simulations presented here, I adopt a Cascadia-like model of the subduction zone interface, where the megathrust is divided into three sections with different sliding characteristics: locked, transition, and continuous creep. The locked zone (<25 km depth) corresponds to the section of the megathrust that generates great earthquakes, the transition zone (∼25-45 km depth) corresponds to the section of the megathrust that generates SSEs, and the continuous creep zone (>45 km depth) corresponds to the section at depth that slides continuously. Results from the simulations are in broad agreement with the characteristics of observed SSEs, for example, their average durations, inter-event times, and slip. The simulations produce complex, high-resolution slip patterns that are remarkably similar to tremor migration patterns observed during SSEs in Cascadia and Nankai. Additionally, the results show a depth-dependence of the characteristics of slip in the transition zone, where the frequency of slip increases with increasing depth. The depth-dependence of slip, and subsequently stress, suggests a spectrum of behaviors along a subduction zone interface, is, in part, related to the creeping zone adjacent to, and below, the transition zone and, in part, related to the constitutive properties in the transition zone. The stressing rate on the seismogenic zone is ∼100x higher during a SSE than during the inter-SSE period, which may give rise to increased activity in the highly stressed region or may initiate nucleation of a great earthquake. Finally, the simulations show a significant slip deficit in the transition zone, which may have significant implications for seismic hazards for coastal cities near subduction zones. |
