Towards ground motion prediction for potential large earthquakes from interseismic locking models

Abstract

Interseismic locking models derived from geodetic data describe slip deficit accumulation on faults, hence indicating the likelihood of future earthquakes. In recent years, locking models have been used to develop dynamic scenarios for potential large earthquakes. However, whether those scenarios are effective in representing the rupture process and ground motion intensity in future earthquakes remains unclear. In this study, we examine the ground motion predictions in locking-based dynamic rupture scenarios by comparing them with the predictions from ground motion models (GMMs) and the observations in a real earthquake. We utilize two locking models as constraints on the stress heterogeneity and obtain synthetic ground motion measures, including the peak ground velocity (PGV) and the peak ground displacement (PGD), through conducting dynamic rupture simulations for M7 earthquakes on the Nicoya megathrust. The predictions are generally consistent with GMMs with some differences in attenuation rate and amplitude in the near field (< 30 km). However, the spatial patterns differ a lot from GMM-based predictions, mainly due to the rupture directivity effect. By comparing with scenarios under homogenous stress conditions, we observe the dependency of earthquake magnitude and rupture directivity on stress heterogeneity. The coseismic slip appears to negatively correlate with stress roughness. Furthermore, the predictions from one locking model capture most of the measurements on the local network during the 2012 Nicoya Mw 7.6 earthquake. Our results underline the necessity of involving rupture dynamics and stress heterogeneities in prescribing the earthquake source and highlight the potential application of locking models in seismic hazard assessment.