Co‐ and Post‐Seismic Mechanisms of the 2020 Mw 6.3 Yutian Earthquake and Local Stress Evolution

Abstract

AbstractThe Mw 6.3 Yutian earthquake, occurred in northwestern Tibet on 25 June 2020, is one of the major events sequentially occurring in the region following the 2008 Mw 7.2, 2012 Mw 6.2, and 2014 Mw 6.9 earthquakes, and is of great significance for studying the tectonic activity and assessing future seismic hazards in the region. In this study, we used Sentinel‐1 Synthetic Aperture Radar images to retrieve co‐ and post‐seismic deformation and to investigate the coseismic rupture behavior of the fault and the mechanisms of postseismic deformation. Based on the slip models of recent four nearby major earthquakes, we explored the local stress evolution, triggering mechanism of the 2020 event and future regional seismic hazards. Postseismic modeling reveals that afterslip on fault patches surrounding the ruptured co‐seismic patches is the main mechanism responsible for the near‐field deformation, with the poroelastic rebound relaxation only accounts for maximumly 25% of the ground displacement and limited impact on the overall deformation pattern. The Coulomb failure stress changes (ΔCFS) suggest that the 2020 Yutian earthquake was inhibited by the 2008 Mw 7.2 earthquake but facilitated by the 2012 Mw 6.2 and 2014 Mw 6.9 earthquakes, resulting in an overall ΔCFS with a large lateral gradient on the 2020 fault. Stress concentrations on nearby major faults indicate increasing chances of seismic hazards in the eastern section of the Altyn Tagh fault at 82.8°E, the western section of the Guozha Co fault at 81.5°E and the entire section of the Ashikule fault.