THE LATE QUATERNARY ACTIVITY CHARACTERISTICS OF THE STRIKE-SLIP FAULTS IN THE TIANSHAN OROGENIC BELT: A CASE STUDY OF THE KAIDUHE FAULT |
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| Authors: | HUANG Wei-liang YANG Xiao-ping LI Sheng-qiang YANG Hai-bo |
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| Affiliation: | 1.College of Geological Engineering and Surveying of Chang'an University/Key Laboratory of Western China Mineral Resources and Geological Engineering, Xi'an 710054, China;2.Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;3.Hebei Earthquake Agency, Shijiazhuang 050021, China |
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| Abstract: | As the most active intracontinental orogenic belt in the world, the Tianshan orogenic belt has complex and diverse internal structural deformation patterns, and among them, the particularly striking is the linear straight U-type valley landscapes which cut inside the mountains by multiple NW-SE and ENE-WSW strike-slip faults. Many of the modern strong earthquakes in Tianshan orogenic belt are closely related to these strike-slip faults. Therefore, it is important to elaborate the activity characteristics of these faults to understand the deformation process inside the Tianshan Mountains belt. This paper focuses on one of the NW-SE right-lateral strike-slip fault (the Kaiduhe Fault), which lies inside the southeastern Tianshan. Typical offset landforms and scarp lineaments on the western segment of the Kaiduhe Fault can be used to study the activity characteristics and strike-slip rate. In particular, the fault cuts through the late Quaternary alluvial fans and a series of river gullies were right-laterally faulted, producing dextral offsets ranging from 3 to 248m. A digital elevation model (DEM)with resolution of 0.25m was established by using multi-angle photogrammetry technique to stripe about 12km linear tectonic landforms along the Kaiduhe Fault. Geological and geomorphic mapping in DEM with 22 high-resolution dextral offset measurements reveals that the dextral offsets can be divide into four groups of 3.5m, 7.0m, 11.8m and 14.5m. It is presumed from the approximately uniformly-spaced offsets that the coseismic offset was 3~4m. In addition, the exposure age of an older alluvial fan surface was about 235.7ka by in situ 10Be terrestrial cosmogenic nuclide method. Combining the exposure ages and the maximum dextral offset of 248m, we found that the strike-slip rate of the Kaiduhe Fault is about 1mm/a. It is found by this study that the Kaiduhe Fault plays an important role in regulating SN compression deformation within Tianshan Mountains, and it should also be the main stress-strain accumulation area which has the risk of occurrence of strong earthquake. |
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| Keywords: | strike-slip fault slip behavior cosmogenic nuclide dating 3D surface modeling Tianshan |
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