Aftershock sequence relocation of the M_S6.8 earthquake on September 5, 2022, in Luding, Sichuan Province

On September 5, 2022, an M_S6.8 earthquake, with a meizoseismal intensity of IX, struck Luding, Sichuan Province, causing severe casualties and economic losses. In this study, we applied the double-difference algorithm (HypoDD) to relocate the mainshock and aftershock sequences within a 25-day period. Precise hypocentral and spatial distributions were determined, with the hypocentral location of the mainshock recorded at (29.59°N, 102.10°E) and a depth of 14.3 km. By analyzing the spatial and temporal distribution of aftershocks and the depth profile of the Luding M_S6.8 earthquake, we estimate that the aftershock fracture zone spans approximately 65 km long and 10–20 km wide. Three distinct aftershock clusters formed along the northern, central, and southern sections of the fault, with focal depths gradually deepening from north to south. Further analysis of the seismic structure revealed that the mainshock and aftershocks were distributed unilaterally along the Xianshuihe fault, specifically along the Moxi segment. This earthquake also activated a secondary, previously hidden fault near Gongga Mountain. Additionally, we examined the seismogenic relationships between the M_S6.8 Luding earthquake and other recent seismic events, including the 2022 M_S6.1 Lushan earthquake, the 2013 M_S7.0 Lushan earthquake, and the 2014 M_S6.3 Kangding earthquake. Using the IDS system, we inverted the hypocentral movement characteristics and obtained the basic parameters of the mainshock rupture, finding a strong correlation between the rupture process and the spatial distribution of aftershocks.