SEISMOLOGY AND GEOLOGY ›› 2014, Vol. 36 ›› Issue (4): 976-990.DOI: 10.3969/j.issn.0253-4967.2014.04.004

• CONTENTS • Previous Articles     Next Articles

DISCOVERY OF THE LATE-QUATERNARY ACTIVITY ALONG THE EASTERN SEGMENT OF MAIDAN FAULT IN SOUTHWEST TIANSHAN AND ITS TECTONIC IMPLICATION

WU Chuan-yong1,2, Alimujiang2, DAI Xun-ye3, WU Guo-dong2, CHEN Jan-bo2   

  1. 1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2. Earthquake Administration of Xinjiang Uygur Autonomous Region, Urumqi 830011, China;
    3. Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China
  • Received:2014-09-12 Online:2014-12-30 Published:2015-01-07

西南天山迈丹断裂东段晚第四纪活动的发现及构造意义

吴传勇1,2, 阿里木江2, 戴训也3, 吴国栋2, 陈建波2   

  1. 1. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029;
    2. 新疆维吾尔自治区地震局, 乌鲁木齐 830011;
    3. 中国地震局兰州地震研究所, 兰州 730000
  • 作者简介:吴传勇,男,1978年生,2005年在中国地震局兰州地震研究所获得构造地质学专业硕士学位,副研究员,现为中国地震局地质研究所在读博士研究生,第四纪地质专业,主要从事活动构造研究,电话:010-62009330,E-mail:cywueq@163.com.
  • 基金资助:

    国家自然科学基金(41102137)和地震动力学国家重点实验室开放基金(LE1413)共同资助

Abstract:

The late-Quaternary deformation characteristics of the boundary fault zones are critical to understanding the crustal deformation of the Tianshan Mountains. Based on remote sensing image interpretation, field surveys, trenching and optically stimulated luminescence dating methods, we obtain the reliable activity evidences of the Maidan Fault in late-Quaternary.
The Maidan Fault is the boundary fault of the Tianshan Mountains and Tarim Basin. The fault, with a total length of 400km and the maximum width about 15~17km, comprises a series of secondary faults. During the late Quaternary, the fault was still very active. The fault dislocated the late-Quaternary landform surfaces, forming obvious scarps on the surfaces. The height of the scarps range several to hundred meters. Trench excavation shows that paleoearthquakes occurred on the faults during late Holocene. The vertical displacement caused by the last paleoearthquake event is above 2m. The different late Quaternary landforms with different vertical displacement heights indicate that several strong earthquake events have occurred on the Maidan Fault since the late Quaternary.
The discovery of activity on the Maidan Fault shows that the deformation does not focus solely on the newly born reverse fault and fold belt. Faults at the root of Kalpin nappe system have also participated in absorbing and partitioning some of the tectonic deformation. This phenomenon may explain why the shortening rate got by geology method of the Kalpin nappe structure is much less than that obtained by GPS. This deformation mode of the Tianshan orogenic belt is obviously different from the piggyback propagation as considered previously. The activities of the Tianshan root faults migrated to the frontal faults of the piedmont nappe, and the root fault activity weakened gradually. But the activity in Kalpin nappe structure does not accord with this mode. The root faults and the frontal faults of the Kalpin nappe structure are all obviously active, which indicates the nappe structure in the southwestern Tianshan is an out-of-sequence, or a non-sequence thrust system. This kind of structure mode brings new challenges to us in constructing seismogenic tectonic models and assessing seismic risk.

Key words: Southwest Tianshan, Maidan Fault, late-Quaternary, tectonic implication

摘要:

利用详细的遥感影像解译、实地调查、探槽开挖以及释光年代学测定的方法对西南天山山前的迈丹断裂东段进行研究, 获得了该断裂晚第四纪以来活动的可靠证据.迈丹断裂东段是一条由多条次级断裂组成的复杂断裂带, 最大宽度可达17km, 晚第四纪以来的活动断错了山前各级地貌面和阶地.探槽开挖表明, 断裂在全新世期间曾发生过断错地表的强震事件, 造成的垂直位错量在2m以上.迈丹断裂晚第四纪以来活动表明, 西南天山地区的构造变形并不完全集中在推覆体前缘新生的逆断裂-背斜带上, 天山根部断裂也吸收了一部分构造变形.这一构造变形模式与已知的北天山前展式的构造变形样式具有明显差异, 柯坪推覆体并不完全遵从断裂新活动不断向盆地方向扩展的特点, 推覆体前缘新生断裂和根部断裂都有较强的活动, 可能是一种无序或反序的构造变形样式.此类构造, 其发震构造模型的建立及强震危险性预测给我们带来新的挑战.

关键词: 西南天山, 迈丹断裂, 晚第四纪, 构造意义

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