3-D coseismic displacement mapping of the 2015 Mw7.8 Gorkha earthquake using multi-viewed InSAR

Abstract

After the 2015 Mw7.8 Gorkha earthquake, geodetic measurements have been extensively used to constrain slip kinematics, fault geometry of the Main Himalayan Thrust (MHT) and earthquake cycle deformation. However, the spatially dense coseismic 3-D displacements remain largely unresolved, owing to the side-looking geometry of SAR images and sparse GPS observations. We improved 3-D displacements by incorporating a strain model in a Bayesian framework, utilizing all available coseismic interferograms and azimuth offsets from Sentinel-1 and ALOS-2 satellites. The coseismic strain map shows that major landslides in large slope areas are spatially consistent with extensional strain. The vertical component illustrates a spatial pattern different from interseismic and postseismic uplift, hinting at diverse contributions from various tectonic uplift processes in the frontal mountain belt. The spatial relationship between the interseismic strain and coseismic deformation suggests a partial release of the accumulated strain, implying a remaining notable seismic hazard around Gorkha.