Source tectonic dynamics features of Jiuzhaigou Ms 7.0 earthquake in Sichuan Province, China
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On August 8, 2017, a Ms 7.0 earthquake occurred 5 km to the west of Jiuzhaigou National Park, causing 25 deaths and injuring 525. The objective of this study was to explore the seismogenic fault of the earthquake and tectonic dynamics of the source rupture. Field investigations, radon activity tests, remote sensing interpretations, and geophysical data analyses were carried out immediately after the earthquake. The Jiuzhaigou earthquake occurred at the intersection of the northern margin of the Minshan uplift belt and the south part of the Wenxian–Maqin fault in the south margin of the West Qinling geosyncline. There are two surface rupture zones trending northwest (NW), which are ground coseismic ruptures caused by concealed earthquake faults. The rupture on the southwest is the structure triggering the earthquake, along the Jiuzhaitiantang–Epicenter–Wuhuahai. The other one on the northeast (Shangsizhai–Zhongcha–Bimang) is a reactivation and extension of the secondary fault trending NW. The source rupture of this earthquake is a strike-slip shear fracture associated with the fault plane trending NW 331° and steeply dipping 75°, which is continuously expanding at both ends. The tectonic dynamics process of the source rupture is that the “Jiuzhaigou protrusion” is left-lateral sheared along the seismogenic fault in the NW direction. Finally, the Maqin fault and the arc fault system at the top of the “Wenxian protrusion” will be gradually broken through sometime in far future, as well as earthquaketriggered landslides will be further occurred along the narrow corridor between the seismogenic faults. The research results revealed the basic geological data and tectonic dynamic mechanism in this earthquake.
KeywordsJiuzhaigou Earthquake Surface rupture Tectonic dynamics Radon activity
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This research was financially supported by the Open Research Fund from the Key Laboratory of Mountain Hazards and Earth Surface Process (Chinese Academy of Sciences) (Grant No. KLMHESP-17-06), the Independent Research Fund from the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology) (Grant No. 40100-00002219). Deep appreciation goes to LIU Kai and Dr TANG Jie for their suggestion and assistance, as well as LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript. We thank anonymous referees and editors for their constructive comments on an earlier version of this paper.
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