Rupture Kinematics and Fault Interactions of the 2022 Mw 6.7 Luding Earthquake: Unilateral Propagation on Conjugate Faults

Abstract

On 5 September 2022, a M_w 6.7 earthquake struck the eastern edge of the Tibetan Plateau, providing a unique opportunity to analyze the Moxi seismic gap of the Xianshuihe fault. We investigate the source rupture process of the 2022 Luding earthquake by combining the back-projection imaging and the joint finite-fault inversion of strong-motion and teleseismic waveforms. We find that the Luding earthquake primarily occurred along conjugate faults, propagating southeastward along the Moxi segment and westward along the Mozigou segment. The aftershock distribution complements the main slip areas, signifying the incomplete stress release during the rupture of the mainshock. Coseismic slips are concentrated in the shallow brittle crust, with low-velocity anomalies at the lower edge of the aftershock area, suggesting middle and lower crustal flow is crucial in guiding coseismic rupture propagation and aftershock distribution. Moreover, the static Coulomb stress changes suggest that the majority of aftershocks occurred in areas with increased stress, underlining the triggering effect of the Luding mainshock. Our study also indicates the increased seismic hazard on neighboring faults, particularly on the northern segment of the Xianshuihe fault, and the Longmenshan and Gongga faults. The numerical simulation of strong ground motion indicates that the overall Peak Ground Velocity (PGV) distribution follows an elliptical shape, with higher PGV values primarily extending southward. Given the steep terrain variations and sedimentary factors in western China, our findings underscore the urgent need for enhanced earthquake resistance and disaster mitigation strategies in tectonically active areas.