The 2022 Ms 5.8 and 6.0 Maerkang Earthquakes: Two Strike-Slip Events Occurred on V-Shaped Faults.

Within four hours on 10 June 2022, three consecutive earthquakes of M_s 5.0 with a maximum magnitude up to M_s 6.0 struck Maerkang, Sichuan, where is supposedly less prone to earthquakes. This article uses seismic observations recorded by the Sichuan Seismic Network to relocate the earthquake sequences and refine velocity models in Maerkang using a double-difference seismic tomography method. The results show that the aftershocks align along northwest and north-northwest directions with a V-shaped pattern, and the M_s 5.8 and 6.0 earthquakes are located in the center of the sequences. The seismogenic faults of the Maerkang earthquake are the two intersecting secondary faults on the east side of the Songgang fault that dip to the northeast and southwest, respectively, with dip angles of about 80°. Analysis of the seismicity parameters and Coulomb stress changes revealed that the M_s 5.8 and 6.0 earthquakes occurred on two separate faults, and the M_s 5.8 earthquake triggered the M_s 6.0 earthquake, while the M_s 6.0 earthquake prevented the rupture of the M_s 5.8 earthquake. The apparent high-velocity anomaly in the upper crust and the low-velocity and high-conductivity layer in the middle-lower crust of the source region suggest that drag forces exerted by the ductile middle-lower crust may have caused the brittle upper crust to move under the eastward extrusion of the Tibetan plateau, leading to the stresses accumulate and release on the causative faults. The Maerkang earthquake highlighted the lateral movement of deep materials and energy redistribution in the intrablock deformation of the Bayan Har block. [ABSTRACT FROM AUTHOR]