Finite-fault slip model of the 2016 M-w 7.5 Chiloe earthquake, southern Chile, estimated from Sentinel-1 data

Abstract

Subduction earthquakes have been widely studied in the Chilean subduction zone, but earthquakes occurring in its southern part have attracted less research interest primarily due to its lower rate of seismic activity. Here I use Sentinel-1 interferometric synthetic aperture radar (InSAR) data and range offset measurements to generate coseismic crustal deformation maps of the 2016 M-w 7.5 Chiloe earthquake in southern Chile. I find a concentrated crustal deformation with ground displacement of approximately 50 cm in the southern part of the Chiloe island. The best fitting fault model shows a pure thrust-fault motion on a shallow dipping plane orienting 4 degrees NNE. The InSAR-determined moment is 2.4 x 10(20) Nm with a shear modulus of 30 GPa, equivalent to M-w 7.56, which is slightly lower than the seismic moment. The model shows that the slip did not reach the trench, and it reruptured part of the fault that ruptured in the 1960 M-w 9.5 earthquake. The 2016 event has only released a small portion of the accumulated strain energy on the 1960 rupture zone, suggesting that the seismic hazard of future great earthquakes in southern Chile is high.