Late Quaternary Tectonic Activity and Slip Rates of Active Faults in the Western Hexi Corridor, NW China
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Late Quaternary Tectonic Activity and Slip Rates of Active Faults in the Western Hexi Corridor, NW China Xingwang Liu *1, 2, Daoyang Yuan1, Qi Su3, Bo Zhang1, 2 1. Lanzhou National Observatory of Geophysics, Lanzhou 730000, China 2. Lanzhou Institute of Geotechnique and Earthquake, China Earthquake Administration, Lanzhou 730000, China 3. School of Earth Science and Engineering, Nanjing University, Nanjing 210046, China Xingwang Liu: https://orcid.org/0000-0001-7794-5772 ABSTRACT: The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward extension of the Altyn Tagh fault. Based on geological and geomorphologic field survey, trench excavation, optically stimulated luminescence dating, we define the fault geometry and kinematic properties of the two faults. Based on fault scarps measurement using differential GPS and 10Be surface exposure dating, we determined vertical slip rate of 0.09±0.01 mm/yr for the Yinwashan fault and 0.1±0.02 mm/yr for the Xinminpu fault. Using the dips observed in trenches and natural sections, we estimated horizontal shortening rates of 0.05±0.03 and 0.23±0.06 mm/yr, respectively. No significant strike slip motion is observed on these two faults, and we infer that this region was dominated by horizontal shortening in the Late Quaternary. Although the shortening rate is quite low on each individual fault, together with other faults in this area, these two faults have an essential role in transferring slip from the eastern end of the Altyn Tagh fault and in accommodating the northeastward growth of Tibetan Plateau. KEY WORDS: Hexi Corridor, Qilian Shan, slip rate, crustal shortening, active fault. 0
INTRODUCTION The Qilian Shan situated at the northeastern boundary of the Tibet Plateau (Fig. 1a), has been subjected to rapid uplift and expansion from approximately the Miocene due to the collision between Indian and Eurasian plates (Wang et al., 2016; Yuan et al., 2013; Zheng et al., 2010; George et al., 2001; Tapponnier et al., 2001). Deformation within the Qilian Shan is linked to two large sinistral strike-slip faults, the Altyn Tagh and the Haiyuan faults (Fig. 1a). A large number of active folds and faults have developed to absorb the sinistral displacement between the two faults (Peng et al., 2018; Zhang et al., 2018; Liu et al., 2017; Zheng et al., 2013a, b; Champagnac et al., 2010; Hetzel et al., 2004, 2002; van der Woerd et al., 2001; Meyer et al., 1998). Located at the northwestern boundary of the Qilian Shan, the Altyn Tagh fault has a significant role in transferring and absorbing the convergence between the Indian and Eurasian plates (Xu et al., 2005; Tapponnier et al., 2001). Total slip, slip rate, and eastward growth of the Altyn Tagh fault constitute important parameters for elucidating the expansion and geodynamics of the Tibetan Plateau. However, it remains controversial on the eastern end of the Altyn Tagh fa
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