Deriving Rupture Scenarios From Interseismic Locking Distributions Along the Subduction Megathrust

Abstract

Given recent advances in geodetic data, interseismic locking models along the megathrust now become useful to qualitatively evaluate future earthquake potential. However, an individual earthquake's true rupture potential is challenging, as it depends on more than just a static image of prior locking. Here, we test the determinism of interseismic locking models using spontaneous rupture simulations and the well-resolved processes associated with the 2012 moment magnitude (Mw) 7.6 Nicoya earthquake. To do so, we estimate initial megathrust stress from locking by assuming that the entire slip deficit will be released in the next megathrust earthquake. Then we initiate spontaneous ruptures at the hypocenter of the 2012 Nicoya earthquake. We find scenarios that approximate the same coseismic slip distribution and final earthquake moment magnitude as obtained from seismic and geodetic observations, demonstrating that deriving potential rupture scenarios from interseismic locking is feasible. We also find that spontaneous rupture scenarios from different locking models differ in moment rate duration and thus ground motion prediction, although the final slip distribution and moment magnitude were similar. The results highlight that quantifying rupture scenarios and ground motions from reliable locking models by dynamic rupture simulations can be an effective tool for seismic hazard assessment in subduction zones.