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  李安,杨晓平,冉勇康,黄伟亮,张玲,徐良鑫,刘华国,李胜强.南天山低角度逆断层古地震破裂变形模式[J].震灾防御技术,2016,11(2):173-185, DOI:10.11899/zzfy20160201.

南天山低角度逆断层古地震破裂变形模式
摘要:    近年来逆冲型破坏性地震频发,这对于逆冲型破裂的古地震研究方法提出了新的要求。由于逆断层角度的变化,在地震中可能表现出截然不同的破裂样式。通过对南天山大量古地震探槽开挖和古地震事件分析研究中发现,低角度逆断层的古地震具有一些常见的破裂类型。本文中挑选了位于南天山三个重要山前逆断裂褶皱带:西段柯坪推覆系、中段库车坳陷的秋里塔格褶皱带和东段焉耆盆地北缘和静逆断裂褶皱带的7个典型探槽剖面,对这类低角度逆断层的古地震进行变形模式、事件识别和位移量计算的总结归纳。低角度逆断层古地震破裂具有以下几种样式并具有各自识别古地震事件和计算位移量的方法:①一条断面对应一次事件的破裂形式,利用断面上断点位置识别古地震事件并判断事件的先后顺序。每个断面各自的位移量正好代表一次事件的位移量。②单条断面多次破裂的样式可以通过上下不同地层的位错量差异判断古地震事件,各个相邻地层之间的位错量差值代表古地震事件的位移量。③多条断面同时破裂的情况表现为多条断面被相同一套地层覆盖,事件位移量为多条断面的位错量之和。④挠曲变形和“推土机”作用是低角度逆断层古地震破裂常见的变形方式,这部分变形量不能忽略,可以通过线平衡和面平衡方法获得断层水平缩短量。
作者单位
李安 中国地震局地壳应力研究所地壳动力学重点实验室北京 100085中国地震局地质研究所活动构造与活动火山重点实验室北京 100029 
杨晓平 中国地震局地质研究所活动构造与活动火山重点实验室北京 100029 
冉勇康 中国地震局地质研究所活动构造与活动火山重点实验室北京 100029 
黄伟亮 中国地震局地质研究所活动构造与活动火山重点实验室北京 100029 
张玲 中国地震局地质研究所活动构造与活动火山重点实验室北京 100029 
徐良鑫 陕西省地震局西安 710068 
刘华国 中国地震局震害防御中心北京 100029 
李胜强 中国地震局地质研究所活动构造与活动火山重点实验室北京 100029 
关  键  词:古地震  低角度逆断层  南天山
DOI:10.11899/zzfy20160201
基金项目:国家自然科学基金青年科学基金项目(41402185);中国地震局地壳应力研究所中央级公益科研院所基本科研业务专项资助项目(ZDJ2014-12)和全国地震监视防御区活动断层地震危险性评价项目(1521044025)共同资助。
收稿日期:2016-03-30
作者简介:李安,男,生于1983年。博士,助理研究员。主要研究方向:活动构造和古地震。E-mail: antares_lee@163.com
通讯作者:
The Paleoearthquake Deformation Model of the Low-angle Thrust Fault in the South Tianshan
Abstract:      In recent year, the thrust earthquake is occurred frequently. Because the angle of thrust fault is changed, the research methods of thrust earthquake also need to be changed. The deformation model of thrust earthquake shows some different types. The more paleoearthquake researches show the low-angle thrust paleoearthquake have some familiar rupture types. In this paper, we choose seven classic profiles of earthquake trench to discuss the event recognition and the displacement of the paleoearthquake. They respectively sit in the Kalpintage fault of the Kalpin thrust system, the Qiulitage fault of the Kuqa depression and the Hejing fault of the Yanqi basin in the South Tianshan. The conclusion is that the low-angle thrust earthquake has several common models. Different models have different methods to recognition events and to calculation displacements. (1) One fault to one event correspondence model: the time sequence can be confirmed by the position of the upper faulted point. Each displacement of fault represents the displacement of one earthquake event. (2) One fault ruptured in multiple events model: event times can be decided by difference displacements of neighboring stratums and the difference of displacements of stratum represent the displacement of earthquake events. (3) Multiple faults to one event correspondence model: one stratum covered multiple faults, and the displacement of event is the total displacement of all faults. (4) The fold deformation and “bulldozer model” is also a familiar rupture model of the low-angle thrust earthquake. This deformation is not ignore and can be calculated by line balance method or area balance method.
Keywords:  Paleoearthquake  The low-angle thrust fault  South Tianshan
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