李满^1,2,,
肖骑彬^1,2,,,
喻国^1,2
1. 中国地震局地质研究所, 北京 100029
2. 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

基金项目: 国家自然科学基金（41974091，41274080，40974042），中国地震局地质研究所所长基金（IGCEA1907），地震动力学国家重点实验室课题（LED2016A03）资助


详细信息

作者简介: 李满, 男, 1994年生, 中国地震局地质研究所硕士研究生, 主要从事大地电磁测深研究.E-mail:liman2458@163.com

通讯作者: 肖骑彬, 男, 1974年生, 研究员.E-mail:xqbchina@sina.com

中图分类号: P319;P313

收稿日期:2020-04-14
修回日期:2020-07-29
上线日期:2020-11-05

Electrical structure of the Altyn Tagh fault at the Changma section and its tectonic significance

LI Man^1,2,,
XIAO QiBin^1,2,,,
YU Guo^1,2
1. Institute of Geology, China Earthquake Administration, Beijing 100029, China
2. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China


More Information

Corresponding author: XIAO QiBin,E-mail:xqbchina@sina.com

MSC: P319;P313

--> Received Date: 14 April 2020
Revised Date: 29 July 2020
Available Online: 05 November 2020


摘要
摘要:阿尔金断裂带东段走滑速率沿断裂走向方向存在明显的流失现象，有关阿尔金断裂带的影响范围及走滑速率变化的机制需要有更多的深部结构证据来提供支撑.本文以阿尔金断裂带昌马段为窗口，获取了4条横穿阿尔金断裂带及相邻地区的大地电磁测深剖面.二维电性剖面显示在阿尔金断裂带北侧中上地壳以连续的高阻体为主，而南侧祁连山内部的深部电性结构在横向上有较为复杂的变化.这一点与区域构造背景相对应，即北侧的塔里木盆地东缘依然具有较好的整体性，南侧的祁连山是青藏高原北缘生长的最前端，变形强烈.在断裂带的结构特征上，阿尔金断裂带沿走向方向的切割深度在昌马盆地西侧发生了显著的降低，与阿尔金断裂带相对应的电性边界在这里向南偏移了约15 km，对应F18断裂，并与昌马盆地相接.祁连山北部的断裂带，包括昌马断裂、旱峡—大黄沟断裂总体呈现出低角度南倾的样式，切过高阻异常体的顶部.虽然昌马盆地可以起到连接断裂带的阶区的作用，将部分阿尔金断裂的走滑分量转移到盆地南侧的昌马断裂上，但是昌马断裂的走滑速率从西向东是增加的，东侧的走滑速率甚至大于阿尔金断裂沿走向方向的流失分量.我们认为在青藏高原北部主要断裂带的活动还是受印度—欧亚板块碰撞引起的远程挤压效应的影响，包括阿尔金断裂以及祁连山内部系列断层都处于斜向挤压应力环境.在这种基本构造模式下，阿尔金断裂、断裂F18、昌马盆地、昌马断裂构成了一个局部的走滑速率分解-转换-吸收体系，对局部应力状态产生影响.
关键词: 大地电磁测深/
二维电性结构/
走滑速率分解/
阿尔金断裂带/
青藏北缘

Abstract:At the eastern segment of the Altyn Tagh fault, the loss in strike-slip rate along the fault trace has been observed. As for the influence of the Altyn Tagh fault and the mechanism for variations in its strike-slip rates, additional evidences of the deep structure are needed. In this article, the Changma section of the Altyn Tagh fault is taken as a window for discussing the proposed problems. The magnetotelluric (MT) data along four profiles across the Altyn Tagh fault and the adjacent areas have been collected. The two-dimensional (2D) electrical resistivity model of each profile is obtained with a mature 2D inversion technique. In the electrical resistivity profiles, the mid-upper crust north to the Altyn Tagh fault is dominated by continuous high-resistivity bodies; while the electrical resistivity structure inside the Qilian Shan is complex with different anomalies in lateral direction. This general image is consistent with the regional tectonic setting. That is, the eastern margin of the Tarim Basin is in good integrity; while the Qilian Shan, as the leading edge of the growth of the northern Tibetan Plateau, is experiencing strong deformation. The electrical resistivity structure also reveals the variations of the faults in space. The cutting depth of the Altyn Tagh fault decreases significantly along its strike direction in the west of the Changma basin. The Altyn Tagh fault imaged as the resistivity contrast offsets southward about 15 km here, corresponding to a fault F18 and connecting with the Changma basin. The faults inside the north part of the Qilian Shan, including the Changma fault and the Hanxia-Dahuanggou fault, are generally in south and low-angle dipping direction. These faults cut through the top of high-resistivity anomalies. The Changma basin can act as a step-over bridging the faults here, so the strike-slip component of the Altyn Tagh fault is partly transferred to the Changma fault at the south side of the basin. Nevertheless, the Changma fault shows increasing strike-slip rate from west to east, the strike slip rate on the east section of this fault is even greater than the loss amount of the Altyn Tagh fault along its strike direction. Therefore, we consider that the major faults at the northern Tibetan Plateau are accommodating the compression strain by the remote effect of the India-Eurasia collision. The Altyn Tagh fault and the active faults inside the Qilian Shan are under transpression setting. Under this basic tectonic mode, the Altyn Tagh fault, F18, Changma basin, and the Changma fault constitute a local decomposition-conversion-accommodation system for the strike-slip rate; this system only affects local stress.
Key words:Magnetotellurics/
Two-dimensional electrical structure/
Decomposition of strike-slip rate/
Altyn Tagh fault/
Northern Tibetan plateau



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