Coseismic deformation of the 19 August 2018 Mw 7.2 Lombok earthquakes, Indonesia, estimated through InSAR and GPS observations

This study investigates the distribution of coseismic slip of the 19th August 2018 M w 7.2 Lombok earthquakes, Indonesia, using Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) data. Two look directions on ascending, with a maximum displacement of 27 cm and 35 cm, and one on descending of Sentinel-1 SAR data, with a maximum displacement of 12 cm, are used. In addition, static offsets from the GPS data, which are located at the most western part of the island and the northern part of the island, detect ~ 2 cm and ~ 5 cm coseismic displacement due to the earthquake. Using combined InSAR and GPS data, this study estimates the fault location, fault geometry and the coseismic slip distribution by a joint inversion using a trans-dimensional Bayesian method. This method solves for the contiguous area of the fault that is allowed to slip in the inversion whilst also solving for the magnitude. This dampens the spurious smoothing that can occur in distributed slip solutions, in particular with far-field geodetic data or deep sources. The maximum slip of ~ 3.5 m is located at deeper portion of the fault at ~ 21 km, adjacent to the epicenter of the earthquake. This study demonstrates that the coseismic slip of the 19th August 2018 earthquakes occurred on a structure further south towards Lombok, a parallel fault structure with Flores back arc thrust.