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Abstract The left-lateral slip rate of the Tianjingshan fault (TJSF) has been debated for several decades. Here, we measured displacements of geomorphic landforms and dated landform ages at two sites along the TJSF, to determine a late Pleistocene to Holocene slip rate of ~1.1 ± 0.2 mm/yr. We also derived a slip rate of ~1.1 ± 0.5 mm/yr using modern GPS data. Finally, by correlating available offset measurements with trenching-derived paleoseismic data, we obtained an average Holocene slip rate of ~1.2 ± 0.1 mm/yr for the TJSF. These fault slip rates over different time scales are in good agreement and are well constrained to 1.1 ± 0.2 mm/yr. The kinematics of the TJSF suggest that the TJSF has played an important role in accommodating the tectonic deformation of the northeastern Tibetan Plateau. Highlights • The slip rates of the TJSF over different time scales are in good agreement and are well constrained to 1.1 ± 0.2 mm/yr; • The fault behavior of the TJSF is characterized by a lower left-lateral slip rate. • The TJSF accommodates complex deformation between the Tibetan Plateau, Alashan block, and Ordos block. [ABSTRACT FROM AUTHOR]

The West Helanshan fault is situated at the junction of the northeastern Tibetan Plateau, Alxa, and Ordos blocks, providing an opportunity to investigate the deformation in the transitional zone between the contractional northeastern Tibetan Plateau and extensional North China. Using field investigations and satellite imagery interpretations, we determined detailed geometry and kinematics of the West Helanshan fault. The West Helanshan fault is divided into three segments, including the northern, middle, and southern segments, based on varying fault strike, slip sense, and geomorphic expression. The northern and middle segments are dominated by right-lateral strike-slip motion as indicated by linear fault traces, horizontally offset streams and terrace risers, relatively insignificant vertical offset, and frequently changing facing direction of fault scarps. The late Quaternary right-slip rate is estimated to be 0.2–0.4 mm/yr, which is relatively low comparing with other strike-slip faults in the northeastern Tibetan Plateau, based on 10Be-dated offset fluvial/alluvial surfaces. The southern segment shows conspicuous fault scarps with significant systematic vertical offset, which has a reverse component as revealed in the trench. The timing of the most recent earthquake revealed in the trench is constrained to be between 6.2 ± 0.7 ka and 5.9 ± 0.4 ka. Notably, the West Helanshan fault cuts through the city center of Azuoqi town, which is the capital of Azuoqi county and has about 100,000 residents, carrying high potential earthquake hazard in the future. Finally, combining the regional fault geometry and kinematics with GPS observations, we propose a limited north-northeastward extrusion model for the southern Alxa Block. • The West Helanshan fault is dominated by right-lateral strike-slip motion. • The most recent earthquake occurred between 6.2 ± 0.7 ka and 5.9 ± 0.4 ka. • A limited north-northeastward extrusion model is proposed to explain the geometry and kinematics of faults in the southern Alxa Block. [ABSTRACT FROM AUTHOR]