| 汶川—映秀MS8.0地震的发震断裂带和形成的深层动力学响应 |
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| 引用本文： | 滕吉文,皮娇龙,杨辉,闫雅芬,张永谦,阮小敏,胡国泽.汶川—映秀MS8.0地震的发震断裂带和形成的深层动力学响应[J].地球物理学报,2014,57(2):392-403. |
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| 作者姓名： | 滕吉文 皮娇龙 杨辉 闫雅芬 张永谦 阮小敏 胡国泽 |
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| 作者单位： | 中国科学院地质与地球物理研究所, 北京 100029 |
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| 基金项目： | 华北克拉通破坏重大研究计划项目(90914012);国家重点基础研究发展规划项目(973项目)“汶川主余震序列的特点和发生机理研究”(2008CB425701);汶川地震断裂带科学钻探(2008)项目联合资助 |
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| 摘 要： | 在印度洋板块与欧亚板块的碰撞-挤压作用下，不仅形成了喜马拉雅弧形山造山带，而且导致其东部弧顶—东构造结似一尖楔沿NNE方向插入青藏高原的东北缘.造成了巴颜喀拉块体和龙门山断裂系深、浅部构造强烈活动和变形，并导致高原腹地壳、幔物质以大型走滑断裂为通道边界向E-ES方向运移.2008年5月12日汶川—映秀MS8.0地震就发生在这相对活动的巴颜喀拉块体与相对稳定的四川盆地之间的龙门山断裂系辖区内.基于该区深部壳、幔结构和主震（MS8.0）与7万多次余震震中位置与震源深度的展布研究表明，汶川—映秀MS8.0地震的发震断裂不是震中在地表投影位置附近，而是龙门山断裂系3条以不同角度西倾、且向下在15±5 km深处汇聚的断裂带CF.该发震断裂带不是一条简单的线性断裂带，而是一半径为5 km左右的柱状震源体，沿NE向展布.在青藏高原东北缘深部物质向东与向东南运动过程中地壳各层整体逐渐抬升，且在龙门山断裂系地带为减薄的转折部位，而地壳低速层却在这里尖灭.在两陆-陆板块碰撞力系作用下，壳、幔介质以上地壳底部低速层（深20±5 km）为上滑移面，并与上地壳解耦，而在深处则以岩石圈底部漂曳的软流层顶部（深100±10 km）为下滑移，故下地壳和上地幔盖层物质才能同步运动.它们在四川盆地高速“刚性”壳、幔物质阻隔下，龙门山断裂系的3条向下汇聚的断裂带与下地壳和上地幔盖层物质同步沿龙门山断裂系的断层面向上逆冲，当向上与向下同步运动的固态壳、幔介质二者在15±5 km深处强烈碰撞时激发了这次MS8.0地震和一系列强余震的发生和发展.基于上述可见，对强烈地震孕育，发生和发展的深部介质与构造环境，深部物质与能量的交换、运移和深层动力过程的研究乃核心所在.
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| 关 键 词： | 汶川—映秀MS8.0地震 发震断裂 上、下滑动面 下地壳和上地幔盖层物质同步运动 深层动力过程 |
| 收稿时间： | 2013-04-06 |
Wenchuan-Yingxiu MS8.0 earthquake seismogenic faults and deep dynamic response |
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| TENG Ji-Wen;PI Jiao-Long;YANG Hui;YAN Ya-Fen;ZHANG Yong-Qian;RUAN Xiao-Min;HU Guo-Ze.Wenchuan-Yingxiu MS8.0 earthquake seismogenic faults and deep dynamic response[J].Chinese Journal of Geophysics,2014,57(2):392-403. |
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| Authors: | TENG Ji-Wen;PI Jiao-Long;YANG Hui;YAN Ya-Fen;ZHANG Yong-Qian;RUAN Xiao-Min;HU Guo-Ze |
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| Institution: | Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China |
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| Abstract: | It is obvious that the India-Eurasia collision has formed the giant arc-like Himalayan belt. At the eastern Himalayan syntaxis, the Indian subcontinent plunges into the Tibetan plateau in NNE direction. Not only resulted in the Bayan Har block and Longmenshan fault system strong tectonic activity and deformation, but also resulted in the material of the hinterland of the plateau crust and upper mantle in the E-ES direction of migration to large strike-slip fault boundary for the channel. The Wenchuan-Yingxiu MS8.0 earthquake of 2008, occurred on the Longmenshan fault system which lies in between the relative activities of the Bayan Har block and relatively stable Sichuan Basin. In the light of the structure of the crust and upper mantle and the distribution of the epicenter and focal depth of the main shock and its more than 70000 aftershaks, the seismogenic fault of Wenchuan-Yingxiu MS8.0 earthquake is not the pojection position of the epicenter in surface. Three westly-vergent thrust faults seen on the surface in the Longmenshan extend downward at different angles and converge at depth 15±5 km, so it produced the convergence fracture (CF). Therefore this shear fault zone is the real triggering seismic fault which is responsible for the MS8.0 event. It is actually a column-shaped source body striking in NE with radius 5 km centered at depth 15±5 km. In the process of deep material eastward and southeastern movement, the whole curst gradually rising and the Longmenshan fault system thinned then crust low velocity layer pinched in the northeastern margin of Qinghai-Tibet Plateau. There are two detachment interfaces at depth in this region, one is the low-velocity layer at depth 20~25 km in the upper and middle crust, the other is the top of the astheonsphere. Along these two interfaces, the materials of the lower crust and the lid in the upper mantle simultaneously transfer toward east. Due to the covering strata hinder of the deep rigid substance below the Sichuan basin, the material of the lower crust and upper mantle moves upward (thrusts) at a steep angle along the Longmenshan. Under the intense exchange of matter and energy, the source medium ruptures suddenly at a large scale to release a huge amount of elastic strain, resulting in the Wenchuan MS8.0 earthquake. Based on the above, it is the key that we study the strong earthquake preparation, occurrence and development for deep environment of medium and structure and deep material and energy exchange, migration and deep dynamic process. |
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| Keywords: | Wenchuan-Yingxiu MS8 0 earthquake Seismogenic fault Upper and lower sliding surface The lower crust and upper mantle material synchronous motion Deep dynamic response |
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