Kinematic rupture process of the 2014 Chile<i>M</i>_w8.1 earthquake constrained by strong-motion, GPS static offsets and teleseismic data

Abstract

On 2014 April 1, a magnitude Mw 8.1 interplate thrust earthquake ruptured a densely instrumented region of Iquique seismic gap in northern Chile. The abundant data sets near and around the rupture zone provide a unique opportunity to study the detailed source process of this megathrust earthquake. We retrieved the spatial and temporal distributions of slip during the main shock and one strong aftershock through a joint inversion of teleseismic records, GPS offsets and strong motion data. The main shock rupture initiated at a focal depth of about 25 km and propagated around the hypocentre. The peak slip amplitude in the model is ∼6.5 m, located in the southeast of the hypocentre. The major slip patch is located around the hypocentre, spanning ∼150 km along dip and ∼160 km along strike. The associated static stress drop is ∼3 MPa. Most of the seismic moment was released within 150 s. The total seismic moment of our preferred model is 1.72 × 1021 N m, equivalent to Mw 8.1. For the strong aftershock on 2014 April 3, the slip mainly occurred in a relatively compact area, and the major slip area surrounded the hypocentre with the peak amplitude of ∼2.5 m. There is a secondary slip patch located downdip from the hypocentre with the peak slip of ∼2.1 m. The total seismic moment is about 3.9 × 1020 N m, equivalent to Mw 7.7. Between the rupture areas of the main shock and the 2007 November 14 Mw 7.7 Antofagasta, Chile earthquake, there is an earthquake vacant zone with a total length of about 150 km. Historically, if there is no big earthquake or obvious aseismic creep occurring in this area, it has a great potential of generating strong earthquakes with magnitude larger than Mw 7.0 in the future.