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Fault interaction and strain partitioning deduced from deformed fluvial terraces of the Eastern North Qilian foreland, NE Tibetan Plateau
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  • Xiu HU,
  • Yiran Wang,
  • Wei-Tao Wang,
  • Michael Oskin,
  • Zhigang Zhi Li,
  • Jinghao Lei,
  • Youli Li,
  • Peizhen Zhang,
  • Wenjun Zheng,
  • Kairong Lin,
  • Shanfeng Xiao,
  • Honghua Lu,
  • Yi-Peng Zhang,
  • Ruizhi Jin,
  • Qingri Liu,
  • Yuezhi Zhong
Xiu HU
Sun Yat-Sen university
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Yiran Wang
University of California, Davis

Corresponding Author:[email protected]

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Wei-Tao Wang
School of earth science and geological engineering, Sun Yan-Sen University
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Michael Oskin
University of California, Davis
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Zhigang Zhi Li
School of Earth Sciences and Engineering, Sun Yat-sen University
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Jinghao Lei
Key Laboratory of Earth Surface Processes of Ministry of Education, Peking University, Beijing 100871, China
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Youli Li
Peking University
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Peizhen Zhang
School of Earth Sciences and Engineering, Sun Yat-sen University
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Wenjun Zheng
Guangdong Provincial Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-Sen University
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Kairong Lin
Sun Yat-sen University
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Shanfeng Xiao
Soochow University
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Honghua Lu
Key Laboratory of Geographic Information Science of Ministry of Education, School of Geographic Sciences, East China Normal University
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Yi-Peng Zhang
School of Earth Science and Geological Engineering, Sun Yat-Sen University
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Ruizhi Jin
Sun Yat-Sen University
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Qingri Liu
Key Laboratory of Earth Surface Processes of Ministry of Education, Peking University, Beijing 100871, China
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Yuezhi Zhong
GFZ German Research Centre for Geosciences
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Abstract

Faulting and folding of basement rocks together accommodate convergence within continental orogens, forming complex zones of intraplate deformation shaped by the fault interaction. Here we use the river terraces along the Dongda river to examine the tectonic deformation patterns of the hinterland and the foreland of the eastern North Qilian Shan, a zone of crustal shortening located at the northeast margin of the Tibetan Plateau. Five Late Pleistocene-Holocene terraces of Dongda river are displaced by three major reverse faults: Minle-Damaying fault, Huangcheng-Ta’erzhuang fault, and Fengle fault, from south to north. Based on displaced terrace treads, we estimated vertical slip rates along the Minle-Damaying fault as 0.7–1.2 mm/a, and along Fengle fault as 0.5–0.7 mm/a. Deformed terraces suggest additional uplift of ~ 0.2 mm/a through folding of the Dahuang Shan anticline. Inhomogeneous uplift of the intermontane basins between the Minle-Damaying fault and the Dahuang Shan anticline indicates a 0.9 ± 0.2 mm/a uplift rate along the Huangcheng-Ta’erzhuang fault. Kinematic modeling of this thrust system shows that deformation propagated northward toward the foreland along a south-dipping 10° décollement rooted into Haiyuan fault at the depth of 20–25 km. This system accommodates 2.7–3.8 mm/a total crustal shortening rate. We suggest this broad thrust belt and the relatively high rate of shortening within this part of the eastern Qilian Shan is as a result of the oblique convergence along a restraining bend of Haiyuan fault system. The elevated shortening rate within this area indicates high potential seismic hazard.