Dynamic rupture of subduction earthquakes located near the trench

Abstract

We perform kinematic and dynamic source inversions of four interplate thrust earthquakes that occurred near the trench at the base of the continental wedge in Northern Chile and we compare them to deeper intraplate events. The magnitudes of these interplate events were between Mw 6.3 and Mw 6.5, with hypocentral depths varying between 17.8 km and 28 km. These earthquakes correspond to one foreshock and three aftershocks of the large 2014 Mw 8.2 Iquique earthquake. The geometry of the seismic rupture obtained from the kinematic and dynamic inversions were similar for the four earthquakes studied and their dynamic source parameters are in accordance with typical interplate earthquakes around Mw 6.5. We compare the dynamic rupture of these events with those of five intraplate, intermediate-depth earthquakes that occurred in Northern Chile, Japan, Argentina and Mexico with depths between 57 km and 250 km. We also compare these events with the Mw 6.9 Valparaiso earthquake that was also a shallow interplate thrust event. Results show that the main dynamic parameters of the interplate events (stress in the nucleation zone, overall stress drop and fracture energy rate) were smaller than those of the intraplate intermediate-depth earthquakes. Furthermore, we compare our results with those obtained with several methodologies commonly used to estimate values of stress drop, fault radius and corner frequency. We find some minor differences between them for most of the earthquakes analyzed. Finally, we infer from our results that the studied area, located in the subduction interface zone near the trench, is suitable for earthquake nucleation of small to moderate earthquakes and does not represent a barrier for a future large tsunamigenic rupture.