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

摘要： 以乌鲁木齐市建成区和规划区作为探测目标区,对区内的活动断层及其深部发震构造进行了系统的探测,对活动断层的危险性和危害性进行了初步评价。根据断层活动性鉴定,确定目标区内存在2组全新世活动断层,即王家沟断层组和九家湾断层组。前者为近EW向的北倾逆断层,后者为NE走向的北倾正断层。晚更新世活动断层为八钢-石化隐伏断层、西山断层、碗窑沟断层和白杨南沟断层。深部发震构造探测揭示出目标区所处的北天山山前薄皮推覆构造及其前缘逆断层-褶皱的清楚结构,结合流动地震观测和小震精确定位等,建立了目标区活动断层的发震构造模型。通过古地震探槽和地震活动性研究对目标区全新世活动断层和晚更新世活动断层的地震危险性进行了评价;并在此基础上对可能发生的直下型大地震所引起的强地震动进行了预测,对全新世活动断层可能产生的地表错动带和晚更新世活动断层可能引起的地表变形带进行了预测。

关键词: 活动断层, 地震危险性, 乌鲁木齐, 天山