Fine geometric structures and characteristics of present-day activity of the Tianshui–Baoji segment of the West Qinling Fault, northeastern margin of the Tibetan Plateau

Abstract

Accurately delineating the fine geometric structures of active faults and assessing their present-day activity are of paramount importance for studying regional fault tectonics and evaluating seismic risk. The West Qinling Fault (WQLF) is situated in a critical zone where material from the Tibetan Plateau is extruded towards the northeast, and the fine geometric structures, kinematic characteristics, and present-day activity of its eastern segment (Tianshui–Baoji segment) can provide important insights into the mechanisms of structural transition at the termination of strike-slip faults and the mode of material expansion in the plateau. In this study, the spatial distribution of the Tianshui–Baoji segment and the characteristics of present-day activity are systematically investigated through detailed interpretations of high-resolution satellite images, digital elevation models (DEMs), unmanned aerial vehicle (UAV) images, geological and geomorphological field surveys, and isotopic dating techniques. The results indicate that the Tianshui–Baoji segment, which begins as a single fault, gradually splays into multiple branching faults towards the east. Both the main fault and these branches have remained active since the Late Pleistocene and even during the Holocene, thus warranting attention to the seismic risk potential in the eastern segment of the WQLF, particularly at its termination. Moreover, the splay of the Tianshui–Baoji segment has led to the gradual divergence of the fault activity of the component to the east, reducing the maximum magnitude of seismic events at the fault terminus and resulting in significant differences in the seismic recurrence intervals between the eastern segment and the central segments of the WQLF (Zhangxian segment, Gangu–Wushan segment).