乌鲁木齐地区N倾断层系的构造特征
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摘要
乌鲁木齐地区发育有5条N倾的断层,这些断层晚更新世以来均有较为明显的活动迹象,并在地表形成了较为显著的构造标志。通过沿断层大比例尺地质地貌填图、探槽开挖和年代测定,较为准确地获得了断层的最新活动时代、运动性质和特征等问题,并确定出这些断层都是在距今20万年~30万年以来快速翘升形成的。结合深地震反射资料,对乌鲁木齐地区的深部结构进行了分析讨论,从而对N倾断层系的深部构造特征也有了更加清晰的认识,为准确评价这些断层的孕震模式和发震能力提供了可靠的依据。
Urumqi lies at the transform site between the range-front fault-fold system of the North Tianshan and Bogeda nappe structural system.The neotectonics is very strong in this area.There are five N-dipping faults in the Urumqi area which formed on the basis of upwarping range-front fluvial and ice-water deposit platforms of the middle Pleistocene.The TL dating of the samples show that the age of this set gravel platforms is about 200~300 ka.Thus,it can be estimated that the N-dipping fault system was generated by rapid upwarping since the time 200~300 ka B.P.The N-dipping fault system dislocated the gravel platform of the middle or late Pleistocene,generating apparent fault scarps on the surface.The Xishan fault,the Wangjiagou fault set and the Jiujiawan fault set which lie in the west of Urumqi are all frontal faults of the northern Tianshan nappe structural system.They are of recoil faults which are generated by tilting of the Xishan block.The relatively independent structure system converges at the decollement which is located about 10 km below the surface.The kinetic intensity of the Xishan fault is gradually subdued from west to east.The Wanyaogou fault and the Baiyangnangou fault which lie in the east of Urumqi are all branch faults of the Bogeda nappe structural system.They are all recoil fault which are generated from upper fault falt.The Wanyaogou fault converges at the decollement about 5 km below the surface.The Baiyangnangou fault converges at the decollement about 6 km below the surface.The kinetic intensity of the two faults is gradually subdued from east to west.
Urumqi lies at the transform site between the range-front fault-fold system of the North Tianshan and Bogeda nappe structural system.The neotectonics is very strong in this area.There are five N-dipping faults in the Urumqi area which formed on the basis of upwarping range-front fluvial and ice-water deposit platforms of the middle Pleistocene.The TL dating of the samples show that the age of this set gravel platforms is about 200~300 ka.Thus,it can be estimated that the N-dipping fault system was generated by rapid upwarping since the time 200~300 ka B.P.The N-dipping fault system dislocated the gravel platform of the middle or late Pleistocene,generating apparent fault scarps on the surface.The Xishan fault,the Wangjiagou fault set and the Jiujiawan fault set which lie in the west of Urumqi are all frontal faults of the northern Tianshan nappe structural system.They are of recoil faults which are generated by tilting of the Xishan block.The relatively independent structure system converges at the decollement which is located about 10 km below the surface.The kinetic intensity of the Xishan fault is gradually subdued from west to east.The Wanyaogou fault and the Baiyangnangou fault which lie in the east of Urumqi are all branch faults of the Bogeda nappe structural system.They are all recoil fault which are generated from upper fault falt.The Wanyaogou fault converges at the decollement about 5 km below the surface.The Baiyangnangou fault converges at the decollement about 6 km below the surface.The kinetic intensity of the two faults is gradually subdued from east to west.
引文
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①新疆维吾尔自治区地质局.乌鲁木齐幅地质图说明书(1/200 000),1965.
[2]沈军,宋和平,李军.乌鲁木齐城市活断层发震模型初探[J].内陆地震,2007,21(3):193-204.
[3]沈军,宋和平.乌鲁木齐城市活断层探测与地震危险性评价主要成果简介[J].地震地质,2008,30(1):273-288.
[4]冉勇康,陈立春,沈军,等.乌鲁木齐西山断裂组与地表破裂型逆断层古地震识别标志[J].地震地质,2007,29(2):218-235.
[5]吴传勇,沈军,李军,等.乌鲁木齐西山逆断层组的新活动特征[J].中国地震,2008.24(4):337-344.
[6]吴传勇,沈军,李军,等.乌鲁木齐西山断层系的新构造变形特征与机制[J].地震学报,2009,31(1):42-49.
[7]冯先岳.新疆古地震[M].乌鲁木齐:新疆科技卫生出版社,1997.
[8]刘保金,沈军,张先康,等.深地震反射剖面揭示出的天山北缘乌鲁木齐坳陷地壳结构和构造[J].地球物理学报,2007,50(5):1 464-1 472.
[9]乔作山.乌鲁木齐河头屯河流域第四纪地层概要[C]//新疆第四纪地质及冰川地质论文选集.乌鲁木齐:新疆人民出版社,1981,176-183.
[10]韩淑媞,叶玮.乌鲁木齐仓房沟晚更新世沉积环境[C]//新疆大学.干旱区新疆第四纪研究论文集.乌鲁木齐:新疆人民出版社,1985.
[11]张培震,邓起东,杨晓平,等.天山北麓的冰水冲洪积地貌与新构造运动[M]//国家地震局地质研究所.活动断裂研究(4).北京:地震出版社.1995,63-78.
[12]高存海,刘嘉麒.乌鲁木齐河流域的黄土研究[J].第四纪研究,1990,(3):251-260.
①新疆维吾尔自治区地质局.乌鲁木齐幅地质图说明书(1/200 000),1965.
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