Structural geometry of the Urumqi foreland thrust system, northern Tian Shan: Insights into the seismotectonics of the 2013 M 5.1 Urumqi earthquake and deformation pattern in the Urumqi area

Wu, Chuanyong ¹Liu, Jianming ²He, Xiaohui ³Li, Zhigang ³Zheng, Wenjun³

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作者信息

1. China Inst Disaster Prevent
2. Earthquake Agcy Xinjiang Uygur Autonomous Reg
3. Sun Yat Sen Univ
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Abstract

In foreland thrust systems, the complex structural geometry creates greater difficulties in constraining the seismotectonics of moderate magnitude earthquakes without pronounced surface ruptures and in assessing future seismic risk. The 2013 M 5.1 Urumqi earthquake was a moderate event that occurred in the Urumqi foreland thrust system. Based on surface investigations, geological mapping, and interpretations of deep seismic reflection profiles, we suggest that the Urumqi foreland thrust belt is a typical active wedge thrust system. Two connected fault segments of the gently south-dipping blind fault ramp and the north-dipping Xishan back-thrust fault merge at a depth of similar to 11 km and bound the wedge-shaped fault block. Analyses of the focal mechanism and aftershock distribution indicate that the seismogenic fault responsible for the M 5.1 Urumqi event is the south-dipping Xishan fault ramp with a dip angle of similar to 10-30 degrees, which highlights the potential seismic hazards of the unruptured north-dipping Xishan back-thrust ramp. The four fault branches on the hanging wall of the Xishan fault are interpreted as flexural-slip thrusts. Our results indicate that multiple surface ruptures over a 6 km-wide area may form if a large earthquake occurs along the Xishan fault system.

Key words

Northern Tian Shan/Structural geometry/Passive back-thrust/Seismogenic structure/TIEN-SHAN/M-W/QUATERNARY DEFORMATION/PISHAN EARTHQUAKE/TIBETAN PLATEAU/SEISMIC HAZARDS/RUPTURE LENGTH/FAULT/BASIN/TECTONICS

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出版年

2022

Tectonophysics

EISCI

ISSN：0040-1951

参考文献量50

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