SEISMOLOGY AND GEOLOGY ›› 2011, Vol. 33 ›› Issue (4): 789-803.DOI: 10.3969/j.issn.0253-4967.2011.04.005

• Active tectonic • Previous Articles     Next Articles

ACTIVE FAULTS OF THE HAERMODUN ANTICLINE AND THEIR FORMATION MECHANISM IN THE NORTH MARGIN OF THE YANQI BASIN

LI An1, YANG Xiao-ping1, HUANG Wei-liang1, Yiliyaer2   

  1. 1. National Center for Active Fault Studies, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2. Earthquake Administration of Xinjiang Uyger Autonomous Region, Urumqi 830011, China
  • Received:2011-08-23 Revised:2011-11-04 Online:2011-12-30 Published:2012-01-12

焉耆盆地北缘哈尔莫敦背斜区的活动断裂及其形成机制

李安1, 杨晓平1, 黄伟亮1, 伊力亚尔2   

  1. 1. 中国地震局地质研究所, 国家地震活动断层研究中心, 北京 100029;
    2. 新疆维吾尔自治区地震局, 乌鲁木齐 830011
  • 作者简介:李安,男,1983年生,在读博士研究生,研究方向为活动构造,电话: 010-62009127,E-mail: antares_lee@163.com。
  • 基金资助:

    财政部重大专项"我国重点监视防御区活动断层地震危险性评价(南天山和静逆断裂-褶皱带地质填图)"和国家自然科学基金(40572126)共同资助

Abstract:

Reverse fault-anticline is an important structure form in Tianshan area.The study on the syntagmatic relation and formation mechanism between active faults and anticline in reverse fault-anticline will help understand the structure system under extrusion stress.Haermodun anticline is a neogenic thrust-anticline in the north margin of the Yanqi Basin.It is the product of reverse fault extending to the inside of the basin.The main reverse fault of the anticline thrusts inwards the basin,with a dip angle of 30°.The present-day tectonic movement is intense along the fault.By interpreting aerial photos of the Haermodun anticline,measuring the scarp profiles and excavating trenches across the fault,we find that three different types of faults have been developed on the different levels of river terraces crossing the anticline,namely,the main reverse fault in front of the anticline forelimb(southern limb),the back thrust fault on the forelimb and the bending-moment normal fault on the top of the anticline,respectively.The main reverse fault has produced three scarps on T1 terrace,with heights of 4m,0.8m and 1.8m,respectively,and a high scarp on T2 terrace with a height of 16m.The back thrust fault has produced 2-4 reverse scarps,with the height up to 4m The bending-moment normal fault has produced about 10 scarps on all levels of terraces except T1 on the top of anticline,and the height of a single scarp can reach 14.5m.The older the terrace,the higher the total height of scarp.Analysis on the geneses of the three faults reveals that the main reverse fault controls the growth of the Haermodun anticline.The back thrust faults help the main reverse fault release the compressive stress,and the part between the main reverse fault and the back thrust fault is extruded.The bending-moment normal fault is produced in the top of anticline.The top of the anticline is a tensional stress area.Back thrust fault and main reverse fault are synchronous.But the scale of back thrust fault is several times smaller than the main reverse fault.Bending-moment normal faults are synchronous with fold deformation.Accompanying the beginning of fold deformation,the bending-moment normal faults began to expand and grow gradually downwards from the top of anticline,synchronously.

Key words: reverse fault, bending-moment fault, back thrust fault, active anticline, formation mechanism, Yanqi Basin

摘要:

逆断裂-背斜是天山地区一种重要构造形式。对逆断裂-背斜区中的活动断裂和背斜之间的组合关系和形成机制的探讨,有利于帮助我们认识在挤压应力作用下形成的构造系统。焉耆盆地北缘哈尔莫敦背斜是盆地北缘断裂向盆地内扩展的新生逆断裂-背斜。背斜主逆断裂以30°左右的倾角向盆内逆冲,现今构造运动强烈。通过对哈尔莫敦背斜航片解译和陡坎剖面测量以及对断层的探槽开挖,认识到在横穿背斜河流的各级阶地(地貌面)上,形成了3种具有不同性质的断裂,分别为背斜前翼(南翼)前的主逆断裂、背斜前翼(南翼)上的反冲逆断裂和背斜顶部的弯矩正断裂。主逆断裂在T1阶地上形成了3条断层陡坎,高度分别为4m、0.8m和1.8m; 在T2阶地上只形成1条16m的高陡坎。反冲逆断裂在T2阶地面上形成了2~4条反向陡坎,高度可达4m。弯矩正断裂在背斜顶部除T1以外的各级阶地上形成了最多10条的陡坎,单条陡坎高度可达14.5m。阶地越老,断层陡坎总高度也越大。分析3种断裂的成因认为: 主逆断裂控制着哈尔莫敦背斜的发育; 反冲逆断裂协助释放挤压应力,反冲逆断裂和主逆断裂之间部分被挤出; 变形背斜褶皱核部顶端产生局部张应力环境,形成弯矩正断裂。反冲断裂和主逆断裂属于同期发育,但二者规模相差数倍,弯矩正断裂与褶皱变形同期发育,伴随着褶皱变形的起始,同步开始由背斜顶面向下逐步扩展生长。

关键词: 逆断裂, 弯矩断裂, 反冲断裂, 活动背斜, 形成机制, 焉耆盆地

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