Slow‐Slip Recurrent Pattern Changes: Perturbation Responding and Possible Scenarios of Precursor toward a Megathrust Earthquake

Advances in geodetic techniques enable us to detect “slow‐earthquake” transients (e.g., slow‐slip events, SSEs) with improving accuracy and coverage. Recent observations reveal intriguing changes of SSE behavior before and/or after earthquakes. However, the physics behind these observations remain largely unknown. How does SSE pattern change during megathrust earthquake super‐cycle? How do SSEs respond to “external” tectonic perturbations such as stress perturbation from earthquakes, or nontectonic forces such as tidal modulation and seasonal loading? Can SSE pattern changes shed light on the onset of a large earthquake? To address these questions, we employ laboratory‐based rate‐and‐state frictional law on subduction zone faults with realistic frictional properties incorporating megathrust earthquake and SSE regions. We conduct 2‐D/3‐D quasi‐dynamic earthquake cycle simulations to study the “intrinsic” SSE pattern changes as how it evolves at different stages of the earthquake cycle, versus the changes in SSE pattern responding to external stress perturbations. Our results suggest that, despite both intrinsic and perturbation models are capable to introduce large variability in SSE pattern, there are considerable observable characteristics that can be used to differentiate these two models. Without external perturbation the SSE patterns change intrinsically during the super‐cycle. The recurrence interval and peak slip rate of SSEs decrease significantly right before megathrust earthquake and could be used as a potential warning sign. Whereas SSE patterns can vary significantly when perturbed by an earthquake or other tectonic/nontectonic sources. Recurring SSEs can be advanced or delayed by external perturbations, and multiple SSEs can be affected if perturbation is long‐lasting.