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Abstract:
The Luding M6.8 earthquake occurred on September 5, 2022 in Ganzi, Sichuan province, China. The epicenter is located west neighboring to the Moxi segment of the main Xianshuihe fault. Based on GNSS observations of 118 stations within the scope of 350 km from the epicenter, collected from the CMONOC and the CSES, we obtained the coseismic displacement field. The results show that the spatial distribution of is axisymmetric to the seismogenic fault, indicating the sinistral strike slip pattern of the earthquake. The maximum horizontal coseismic displacement was recorded at station SYD5, 40 km epicenter distance, with the magnitudes being -22.0 ± 1.2 mm and 11.6 ± 0.9 mm on the EW and NS components, respectively. The magnitudes of displacements decline to < 5 mm for stations with epicenter distances being > 100 km. There is no remarkable vertical coseismic displacement recorded at these GNSS stations. By setting the geometrical strike and dip angles of the seismogenic fault being 163o and 77o, respectively, we estimated the coseismic slip distribution, indicating that the coseismic slips had ruptured to the surface, mainly distributed at the depths of 0 ~ 15 km within the seimic gap of aftershocks. According to the spatial distribution of the theoretical coseismic displacement field and principal strain field, as well as the Coulomb stress changes on surrounding active faults, the earthquake raises intensive seismic risk at the Shimian - Mianning segment of the Anninghe fault, where it is characterized as fully coupled and located in a significant seimic gap.
