Geodetic Model of the 2017 Mw 6.5 Mainling Earthquake Inferred from GPS and InSAR Data

Abstract

On 17 November 2017, a Mw 6.5 earthquake occurred in Mainling County, Nyingchi City, China. The epicenter was located in the Namche Barwa region of the eastern Himalayan syntaxis. Here, we have derived coseismic deformation from Global Positioning System (GPS) data and ascending Sentinel-1A Synthetic Aperture Radar (SAR) data. Based on a joint inversion of the two datasets, we obtained the coseismic slip distribution along a curved, northeast trending, and high-angle (dip angle of 75°) thrust fault. Our results show that the seismic moment release was 7.49 × 1018 N∙m, corresponding to a moment magnitude of Mw 6.55. The maximum slip was 1.03 m and the main rupture zone extended to a 12 km depth. The earthquake may have been related to the release of strain accumulated during the subduction of the Indian plate beneath the Eurasian continent. We identified a high strain rate and low b-values around the epicentral area before the earthquake, indicating that the earthquake was nucleated under a high strain/stress state. The data indicate two regions, southwest and southeast to the epicenter (the eastern Main Himalaya Thrust and northern end of the Sagaing fault), which remain under high stress/strain conditions and pose a significant seismic hazard.