Coseismic deformation analysis of the 2017 Milin Ms 6.9 earthquake in the Namche Barwa Syntaxis: Implications for regional tectonics

The 2017 Milin earthquake occurred near Namche Barwa on the southeastern Tibetan Plateau. This research employed Sentinel-1 imagery to capture the corresponding coseismic deformation field and adopted a joint inversion approach using geodetic measurements and teleseismic waveform data to assess earthquake mechanics. The coseismic deformation indicated distinct differential movements, indicating a thrust movement of this fault with uplift in northeast side. The calculated seismic moment magnitude was Mw 6.5, with the fault striking of 305° and a dip angle of 72° The earthquake hypocenter was located at a depth of approximately 10 km, and the maximum fault slip was approximately 1.08 m. The event was attributed to the northwestern segment of the Xixingla fault. Numerical simulations indicated a peak ground velocity of approximately 0.3 m/s. The northwestern segment of the Xixingla fault was identified as the seismogenic fault of the event. Furthermore, the Coulomb stress analysis indicates that the earthquake induced stress loading on the Dongju-Milin and Jiali faults. The surface strain analysis reveals a region of high strain adjacent to the fault. The 2017 Milin earthquake occurred because the Xixingla fault underwent predominantly thrust-type sliding due to the continuous tectonic stress induced within the Tibetan Plateau. Notably, the middle segment of the Xixingla fault currently experiences relatively low seismic activity and is in a state of stress and strain accumulation. Thus, strong earthquakes may occur within the middle segment of the Xixingla fault.