Study on Deformation Characteristics of Southeastern Tibetan Plateau and Dynamic Cause of the Luding MS6.8 Earthquake, China

A M_S6.8 earthquake struck Luding Country in Ganzi Prefecture, Sichuan Province on September 5, 2022. The earthquake occurred on the Moxi segment of Xianshuihe fault zone (XFZ), one of the most seismically active faults in the China mainland. In this study, multiple periods of the Global Positioning System (GPS) velocity fields and continuous observational data are collected to analysis the tectonic deformation and evolution characteristics before the Luding earthquake, from the perspectives of the kinematic behaviors of seismogenic faults, the multi-scale strain features around the study region, and the variation of GPS baseline across the epicenter area. Then the following conclusions are obtained: (1) The accelerated compression of baselines SCGZ-SCXJ and SCLH-SCXJ in Bayan Har block indicate that boundary faults are decoupling and accelerated southward and eastward pushing under the influence of the coseismic rupture of Maduo M_S7.4 earthquake, which leads to the acceleration of the strain accumulation and the increase of seismic risk in the divergence area bounded by the southern section of XFZ and the southwestern section of Longmenshan fault zone (LFZ). (2) Luding earthquake located in the weakened region around the edge of the large strike-slip fault zone with high shear strain rate, and the tensile zone of the strain perpendicular to the fault direction, denoting that the reduction of the normal strain in the locked background is strongly related to fault rupture and earthquake nucleation.