The 734 A.D. Tianshui earthquake occurred near Tianshui city in Gansu Province, China, at the northeastern margin of the Tibetan Plateau. A precise study of the seismogenic structure and quantitative parameters of this earthquake is highly important for advancing the understanding of characteristics of seismic hazards in the Loess Plateau region and for scientifically assessing regional seismic risk. Through geological and geomorphological field surveys, some residual surface rupture phenomena from the 734 A.D. Tianshui earthquake were identified. Using unmanned aerial vehicle (UAV) photogrammetry, isotopic dating, visual interpretation of landslide data, and historical data validation, a comprehensive analysis was conducted on the seismogenic structure, scale of the surface rupture zone, magnitude, and coseismic sinistral displacement of this earthquake. Our findings suggest that the 734 A.D. Tianshui earthquake occurred at the eastern end of the Gangu-Wushan segment of the West Qinling Fault (WQLF), with a magnitude of at least Mw 7.1. The maximum coseismic sinistral displacement obtained along the rupture segment is 3.1 ± 0.3 m, with residual surface rupture traces extending for intermittently 25 km. Additionally, the displacement clustering characteristics of typical geomorphic markers were analysed to assess the seismogenic potential at fault terminations. These findings contribute to enhancing the understanding of fault behaviour and seismic hazard characteristics in the northeastern margin of the Tibetan Plateau, providing important insights for regional seismic risk assessment and disaster mitigation.
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