Geodetic model of the 2024 January 22 Mw 7.0 Wushi (northwestern China) earthquake and Mw 5.7 aftershock from inversion of InSAR data

On 2024 January 22, an MW 7.0 earthquake struck the southern sector of the Tian Shan Mountains in Wushi County, northwestern China, causing damage and casualties. In this study, using Interferometric Synthetic Aperture Radar measurements (Sentinel-1 satellites), we constrained the geometry of the fault segment responsible for the seismic event, the coseismic slip distribution, and the source of the subsequent MW 5.7 aftershock deformation. Finally, we evaluated the potential state of stress of the unruptured portions of the causative fault as well as of adjacent fault segments, using the Coulomb stress failure function variations. Our findings indicate rupture along a transpressive left-lateral NNW dipping high-angle fault, associated with the Southern Tian Shan Fault alignment, likely the Maidan fault, with slip up to 3.5 m only occurring between 10 and 20 km depth. The position of the hypocentre with respect to our estimated slip distribution supports the evidence of a marked bilateral ENE-WSW rupture directivity during the mainshock. The modelling of the post-seismic deformation that includes the MW 5.7 aftershock occurred on 2024 January 29, and that is located about 15 km to the south of the mainshock, indicates a main patch with up to 90 cm of slip that may have occurred on a shallow back-thrust segment, in agreement with the observed surface breaks. We propose a potential structural and/or lithological influence on the coseismic rupture extent, consistent with observations from other intracontinental earthquakes. Finally, based on the Coulomb stress distribution computation, we find that the MW 5.7 aftershock was likely triggered by the preceding mainshock and that the Wushi earthquake also increased the stress level at both terminations of the modelled fault plane, particularly along the southwestwards continuation of the Maidan fault. In addition, we also find that a wide up-dip fault patch remained unruptured, and considering that these areas have been dynamically loaded it could represent potential further aseismic deformation and/or future significant ruptures, posing a continuing seismic hazard to Wushi County and surroundings areas.