Kinematic Rupture Process of the 2014 ChileMw 8.1 Earthquake Constrained by Strong-Motion, GPS Static Offsets and Teleseismic Data

mcdavid c. james;

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 Nm, 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 ∼2.5m. There is a secondary slip patch located downdip from the hypocentre with the peak slip of ∼2.1m. The total seismic moment is about 3.9 × 1020 Nm, 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.