Rupture Scenarios and Ground Motion Prediction from Interseismic Locking Models in Nicoya Peninsula, Central America

Seismic hazard evaluation demands accurate ground motion prediction. Dynamic rupture simulation is an effective approach in estimating near-source ground motion. However, it is well known that numerical simulations are dependent on a few factors and how to realistically constrain heterogeneities in future ruptures becomes critical. Interseismic locking models derived from geodetic data have significantly advanced our understanding of loading on faults, which reveals the stress accumulation pattern. Here, we conduct spontaneous rupture simulations with initial stress derived from interseisimic locking models on the megathrust beneath Nicoya Peninsula, Costa Rica, with different nucleation sites. Results show that nucleation site significantly impacts rupture process, eventual slip distribution, and ground motions. To validate the ground motion predictions from those rupture scenarios, we compare the synthetics with high-rate GPS data recorded during the 2012 Nicoya M7.6 earthquake. The average peak ground velocity (PGV) predictions from scenarios derived from Feng's locking model (Feng et al., 2012) are well consistent with observations with misfit <15%. Due to the hypocenter-dependent effects, variations in the PGV are up to ~50% for ruptures nucleating from different positions. Moreover, we compare the spectra of GPS data and synthetics, which show great coherency for the vertical components in the frequency range below 1Hz. In horizontal components, spectrum show some similar characteristics. By comparing the model predictions with near-field high-rate GPS observations, our study demonstrates the feasibility to predict ground motion in future earthquakes by conducting dynamic rupture simulations with constraints from interseismic locking models. Such approach can also be applied in seismic hazard assessment in other subduction zones.