Vertical Slip Rate and Tectonic Context of the Langshan Piedmont Fault, Northwestern Ordos Area, China

Abstract As the Tibetan Plateau expands, its outskirts suffer significant seismic hazards. Remotely affected by the expansion of the Tibetan Plateau, the northwestern Ordos area develops an extensional tectonic setting. The occurrence of destructive earthquakes, such as the 1739 Yinchuan‐Pingluo M 8.0 earthquake, reflects serious tectonic activities in this area. Therefore, studying the activity of the boundary normal faults is crucial. This study calculated the vertical slip rate of the Langshan Piedmont Fault (LPF) and integrated it with the parameters of other faults to develop a quantitative tectonic model of the sub‐blocks in the northwestern Ordos area. Using high‐precision unmanned aerial vehicles, drilling, and two Quaternary dating methods ( 14 C and optically stimulated luminescence), the vertical displacement of the LPF was constrained by the same lacustrine layer in a footwall outcrop and in a hanging wall borehole. The vertical slip rate of the LPF since 51 ka was calculated to be 3.14 ± 1.14 mm/a. The northwestern Ordos area primarily includes parts of the Alxa and Ordos blocks, with the Alxa Block further divided into the Northern Alxa, Bayanhot, and Helanshan sub‐blocks. The LPF is the boundary of the Northern Alxa and Ordos blocks. The Ordos, Bayanhot and Helanshan Sub‐blocks move relative to the Northern Alxa Sub‐block at 1.36 ± 0.30 mm/a (N138.04°), 0.24 ± 0.33 mm/a (N65.34°), 0.26 ± 0.15 mm/a (N133.78°), respectively. Therefore, under the northeastward growth and extrusion of the Tibetan Plateau, the tectonic deformation in northwest Ordos area mainly manifested as the relative movement between the Alxa and Ordos blocks.