Effects of Plate Interface Frictional Heterogeneities on Earthquake Cycle Dynamics in Subduction Zones

Abstract

Subducting seamounts, ridges, and other frictional heterogeneities critically influence megathrust earthquakes and aseismic slip in subduction zones. However, their exact role—whether as asperities that enhance rupture or as barriers that impede it—remains a point of ongoing debate in earthquake physics. In this study, we investigate the influence of barriers on earthquake cycles using both laboratory stick-slip experiments and quasi-dynamic simulations of synthetic natural cases, such as the Alaska-Aleutian subduction zone. In the laboratory, we employ a single-degree-of-freedom spring-block system with controlled frictional heterogeneities, where asperities and barriers are distinguished using sandpapers of differing grit sizes to create velocity-weakening and velocity-strengthening regimes, respectively. Our results show that increasing the area of a single circular barrier within an asperity leads to a transition from periodic stick-slip (seismic events) to aseismic slip beyond a threshold of ~11% of the apparent contact area of the sample. Numerical simulations of a synthetic segmented fault and that of a scaled Alaska-Aleutian subduction zone further demonstrate that a velocity-strengthening patch bounded by velocity-weakening regions on either side can act as a permanent seismic barrier when its along-strike length constitutes ~40% of the rupture segment. This observation aligns with our laboratory findings, where the ratio of the lateral extent of a barrier to the total length of the contact interface along strike (Lb/L) was ~0.4—a critical threshold that marks the transition from seismic to aseismic slip. While the use of grit-based frictional contrasts to mimic asperities and barriers has been employed in prior studies, our work uniquely quantifies the threshold barrier area and along-strike extent required to impose frictional controls on rupture propagation or arrest in subduction faults. These findings demonstrate that the role of frictional barriers depends on both their areal coverage within asperities and their spatial extent along strike, providing new constraints for seismic hazard assessment in subduction zones with heterogeneous plate interfaces.