The earthquake sequence, surface rupture characteristics and engineering effects of the M_S6.9 Qinghai Menyuan earthquake on January 8, 2022

At 01:45 on January 8, 2022, an M_S6.9 earthquake occurred in Menyuan County, Haibei Tibetan Autonomous Prefecture, Qinghai Province. In order to gain a deeper understanding of the activity characteristics of this earthquake, the author conducted a preliminary investigation and analysis of the surface rupture zone and traffic system damage in the Liuhuanggou based on the investigation of earthquake disaster losses, combined with various methods such as drone low altitude photogrammetry and aftershock data analysis. The fault activity was mainly characterized by left-lateral strike-slip motion, accompanied by a certain thrust component, with a maximum left lateral displacement of 3.1 m. At the same time, the earthquake caused serious damage to the Liuhuanggou bridge and the Daliang tunnel of the Lanxin high-speed railway, mainly manifested as beam overturning and sliding, track distortion and deformation, and internal structure displacement and deformation of the tunnel. Finally, this article provides opinions and suggestions on the seismic fortification measures for bridges in the region.