[S-CG45] Science of slow-to-fast earthquakes

[SCG45-P49] Impact of Slow Slip Events on Apparent Plate Coupling and Seismic Hazard

*Louise Maubant^1,2, Sylvain Barbot³, Mathilde Radiguet⁴, Erwan Pathier⁴, William Frank² (1.Earthquake Research Institute, University of Tokyo, Japan, 2.Massachusetts Institute of Technology, USA, 3.University of South California, USA, 4.ISTerre, Université Grenoble Alpes, France)

Keywords:Slow slip event, Rate-and-state, Seismic cycle

Accurate estimates of plate coupling are crucial for assessing seismic hazard, as they provide insights into potential earthquake activity along subduction zones. Geodetic observations over the last 20-30 years have identified low coupling regions in areas such as Mexico, New Zealand, Alaska, and Chile. Some of these regions have experienced significant earthquakes, while others, such as Guerrero in the Mexican subduction zone, have not. Since the 2000s, it has been recognized that subduction zones can host transient deformation at slip rates much slower than typical earthquakes, known as slow slip events (SSEs). These events interact with all phases of the seismic cycle, including the interseismic period, affecting plate coupling estimates.


This study aims to determine if low coupling regions observed over the past two decades can host earthquakes and if slow slip events in deeper subduction zones explain coupling variations over time in the shallower part of the subduction. Using the rate-and-state numerical model Unicycle (Barbot, 2019), we simulate the seismic cycle to explore the relationship between SSEs, low coupling regions, and earthquake occurrence. Our model is based on the Mexican subduction zone. It includes a velocity-weakening area in the shallow part (10-25 km depth) where earthquakes occur every 40-100 years and a deeper region (30-45 km) where slow slip events are hosted. Based on the Guerrero region, our simulations replicate the characteristics of SSEs and investigate their interactions with the seismogenic zone above. Our findings suggest that decoupling can occur in the seismogenic zone at certain points in the seismic cycle, potentially leading to a megathrust earthquake in a low coupling zone. By examining the relationship between SSEs and a megathrust region, we provide insights into the dynamics between slow slip events, low coupling regions, and the occurrence of earthquakes.