Co-seismic Static Stress Field and Stress Triggering of Aftershocks in the 2022 Menyuan Ms 6.9 Earthquake

This study investigates the impact of the magnitude 6.9 Menyuan earthquake in Qinghai, 2022, on surrounding areas using the elastic half-space dislocation model. It calculates the co-seismic displacement and stress fields of the Menyuan earthquake and examines the mainshock's triggering effect on aftershocks based on co-seismic Coulomb stress changes. The results show: (1) The materials converge from the southwest and northeast before dispersing from the northwest and southeast around the epicenter, with subsidence in the southwest and northeast and uplift in the northwest and southeast. (2) Stress-wise, expansion occurs southwest and northeast, while compression occurs northwest and southeast of the epicenter. (3) The Coulomb stress change displays positive and negative areas. At a depth of 5 km, the aftershock triggering ratio of magnitude 3 and above is 33.33%, while at depths of 10 km and 15 km, the aftershock triggering ratio is 100%. (4) The overall pattern of distribution of Coulomb stress variations remains consistent across the different rupture models and different depths, but the distribution in the near-field close to the fault is quite significantly different. Furthermore, the differences in overall stress distribution patterns produced by changes in crustal velocity models and friction coefficients are relatively small compared to those caused by changes in rupture models, although specific numerical discrepancies can occur at certain points.