| 塔里木盆地及邻区岩石圈拆离解耦与盆山格局关系的天然地震分析 |
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| 引用本文： | 李涛,王宗秀.塔里木盆地及邻区岩石圈拆离解耦与盆山格局关系的天然地震分析[J].地学前缘,2005,12(3):125-136. |
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| 作者姓名： | 李涛 王宗秀 |
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| 作者单位： | 中国地震局,地质研究所,北京,100029;中国地质科学院,地质力学研究所,北京,100081 |
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| 基金项目： | 国土资源部国土资源大调查项目 |
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| 摘 要： | 与洋陆俯冲关系不同,在板内汇聚过程中,大陆岩石圈固有的多圈层、多界面结构的特点,使得地块的俯冲变形伴有多圈层顺层拆离解耦的行为,使变形结构复杂化。虽然多圈层界面拆离解耦所引发的地震点群空间分布不像洋陆俯冲关系那么规则完美,但是依据地震群与破裂位置、破裂与岩石圈分层力学特性的依次控制关系,运用深度/频次、平面密度等统计方法,再以各种地球物理实测手段得到的岩石圈结构构造数据作为界面标定依据,还是能够得出诸如拆离解耦的界面深度、界面归属和区域层间变形范围等重要的几何学信息,这些变形几何学、运动学数据是构建大陆岩石圈板内汇聚造山特别是盆山耦合模式时的关键性的依据。文中通过对塔里木盆地及周缘造山带的相关研究,在岩石圈层拆离解耦状态及其与盆山构造格局之间的关系方面得出以下几点认识:(1)塔里木盆地及周缘造山带岩石圈的主拆离解耦层均发育于中地壳,但随各区中地壳的具体深度位置不同而有所差别;(2)塔西南/西昆仑盆山构造耦合关系是构建于岩石圈尺度上的,塔北/南天山盆山耦合关系是构建于地壳尺度上的;(3)地震活动的密集程度及密集带的展布与天山的变形强度、隆升状态和地貌阶段类型的变化规律有着近乎完美的精确匹配关系;(4)塔北/南天山和塔西南/西昆仑对应于岩石圈的强拆离解耦区,塔东北/东天山和塔东南/阿尔金山之间无耦合关系,其边缘带对应于岩石圈弱拆离解耦和无拆离解耦区;(5)塔里木盆地总体上的弱变形状态与其岩石圈弱或未拆离解耦类型占据总面积90%的情形相适应;(6)塔里木地块以驱动、阻挡约束、平移滚筒约束和克拉通过渡等多重“身份”存在于相邻单元“包围”的力学环境中。
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| 关 键 词： | 塔里木盆地 天山 西昆仑 大陆岩石圈 拆离 解耦 盆山耦合 天然地震 |
| 文章编号： | 1005-2321（2005）03-0125-12 |
| 收稿时间： | 2005-03-26 |
| 修稿时间： | 2005-07-15 |
The lithospheric decoupling of the Tarim Basin and surrounding orogenic belts and its relationship with basin-mountain patterns from the analysis of natural earthquake |
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| LI Tao,WANG Zong-xiu.The lithospheric decoupling of the Tarim Basin and surrounding orogenic belts and its relationship with basin-mountain patterns from the analysis of natural earthquake[J].Earth Science Frontiers,2005,12(3):125-136. |
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| Authors: | LI Tao WANG Zong-xiu |
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| Institution: | 1. Institute of Geology, China Seismological Bureau, Beijing 100029. China;2. Institute of Geomechanics .CAGS. Beijing 100081, China |
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| Abstract: | In the process of intraplate convergence of continental lithosphere, parallel-layer detachments commonly occur during the subduction of continental crust, owing to the multi-layer and multi-interface characteristics of the subcontinental lithosphere. This is a different process from the subduction of oceanic crust beneath continents, thereby resulting in more complex deformation patterns. The spatial distribution of epicenters along several interfaces of the detachments is not as regular as that which characterizes the subduction of oceanic crust beneath continents. Nevertheless, taking into consideration earthquake groups, the locations of ruptures, the relationship of ruptures with the multi-layer structure of lithosphere, the density of earthquakes at different depths, and by counting depth vs. frequency of earthquakes, we can identify important geometric patterns. These include the depth to detachments surface, characteristics of interfaces and deformation between layers on regional scale.This information is critical for interpreting the evolution of orogenic structures formed by the intraplate convergence of continental lithosphere, especially the basin-mountain (orogenic belt) dichotomy. In this article, we report our study of the Tarim Basin and the orogenic belts that surround it. This study has enabled us to model the state of continental decoupling and its relationship with basin-orogenic belt tectonic patterns.The salient points of our work are: (1) The main detachments in lithosphere all occur in the middle crust of the Tarim Basin and adjacent orogenic belts; however, these are not the same due to different depths of the middle crust in different areas. (2) The basin-mountain (orogenic belt) dichotomy and coupling between southwestern Tarim and western Kunlun Mountains occurs at the lithospheric scale, whereas the coupling between northern Tarim and southern Tianshan Mountains occurs at the crustal scale. (3) There are good matching relationships among the distribution and density of earthquakes foci and the intensity of deformation, and the state and amount of uplift of Tianshan Mountains, and the associated changes in topographic styles. (4) The northern Tarim Basin-southern Tianshan Mountains (orogen) and southwestern Tarim Basin-western Kunlun Mountains (orogen) boundaries correspond to the strong decoupling zones. But there are no coupling relationships between northeastern Tarim Basin and east Tianshan Mountains, and between southeastern Tarim Basin and Altun Mountains; the boundaries between the basin and the mountains correspond to the weak lithospheric decoupling or no lithospheric decoupling zones. (5) The state of weak deformation of Tarim Basin coincides with the fact that the weak lithospheric decoupling and no decoupling areas reach 90% of the total areal extent of the Tarim Basin. (6) The Tarim block has evolved in a mechanical environment surrounded by adjacent units; it acts as a backstop that blocks horizontal movements. |
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| Keywords: | Tarim Basin Tianshan Mountains western Kunlun Mountains continental lithosphere detachment decoupling basin mountain coupling natural earthquakes |
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