关键词: 活动断层, 地震危险性, 乌鲁木齐, 天山

Abstract: The predominant results of the project "Active fault detecting and seismic risk assessment in Urumqi City" are introduced in this paper. The active faults detecting target region covers the Urumqi City and its urban planning area. Deep seismogenic tectonics of the faults was detected systematically during this project. The seismic risk and damage of the active faults were estimated preliminarily. Two groups of Holocene active faults,namely,Wangjiagou Fault group and Jiujiawan Fault group,were identified in the target region. The Wangjiagou Fault group is composed of four north-dipping thrust faults,while the Jiujiawan Fault group is composed of four north-dipping normal faults. Four late Pleistocene active faults,namely,Bagang-Shihua buried fault,Xishan Fault,Wanyaogou Fault and Bayangnangou Fault,were detected in the target region. A clear image of the thin-skinned thrust system under the city was made by deep seismic profile carried out by this project. Combined with the observation of mobile seismic station array and precise location of micro quakes in the target region,as well as other deep structure detecting results,such as the petroleum seismic profile,two seismic models of the target region were established. The seismic risk of the Holocene active faults and late Pleistocene active fault were estimated by paleo-earthquake trenching and seismicity analysis along the Holocene active faults,as well as the microstructure study along the late Pleistocene active faults. Meanwhile,the strong ground motion generated by potential strong earthquakes directly under the target region was predicted by numerical modeling. The surface displacement and deformation zones of the future strong earthquake along the Holocene and late Pleistocene active faults were estimated.

Key words: active fault, seismic risk, Urumqi City, Tianshan