Dynamic rupture process of the 2022 Menyuan Mw6.6 earthquake, Qinghai, China

On January 8, 2022, a significant Mw 6.6 earthquake struck Menyuan, Qinghai, resulting in substantial surface damage. To investigate the geological context behind the strong surface rupture generated by the Menyuan earthquake and its impact on inhibiting stress release in the eastern section of Tuolaishan fault, this study utilized the spectral element method to simulate the dynamic rupture process of the branching fault on actual terrain. The dynamic rupture simulation revealed that the rupture initiated bilaterally along an upward direction from the initial rupture point. Influenced by a high-speed P-wave anomaly located above the source area, the rupture displayed a non-continuous pattern. As the rupture progressed into the eastern section of Tuolaishan, there was a significant abrupt decrease in both sliprate and slip. Furthermore, the area with a sliprate of approximately 3.6 m/s near the Earth's surface could be considered a strong motion generation zone. The combined influence of these factors, along with their high-frequency radiation, likely played a pivotal role in causing the pronounced coseismic surface deformation during the Menyuan Mw 6.6 earthquake. The spatial distribution of strain, as calculated from the dynamic simulation results, revealed that the southwestern side of the eastern section of Tuolaishan and the northeastern side of the western section of Lenglongling experienced predominantly tensile stresses, with corresponding areas subjected to compression. This observation aligns with the focal mechanism solution and the geological context of the northeastern margin of the Qinghai-Tibet Plateau, where the principal compressive stress direction transitions from north-south to southwest-northeast. Furthermore, the dynamic rupture process in the eastern section of the Tuolaishan was strongly inhibited by the rupture of the branching fault. This resulted in incomplete stress release and a residual seismic magnitude of approximately Mw 5.1. Triggered by Coulomb stress from the Menyuan earthquake, the potential for further rupture in the future is a possibility.