Dynamically Triggered Changes of Plate Interface Coupling in Southern Cascadia

Abstract

In subduction zones, frictional locking on the subduction interface produces year-by-year surface deformation that is measurable with GPS. During the interseismic period of the earthquake cycle, lasting hundreds of years between major earthquakes, these ground motions are usually constant with time because the locking on the plate interface is relatively unchanging. However, at the Mendocino Triple Junction in Northern California, we find evidence for slight changes in GPS interseismic motion within the last decade that challenge the assumption of constant interseismic deformation. Our results suggest changes in interseismic coupling on the southernmost Cascadia Subduction Zone. Interestingly, these coupling changes appear to be related to large offshore earthquakes and are perhaps triggered by the seismic shaking during those events. These results have important implications for our understanding of seismic hazard in subduction zones.