| 西藏高原当雄-亚东地带地壳与上地幔结构和速度分布的爆炸地震研究 |
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| 作者单位： | 中国科学院地球物理研究所 |
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| 摘 要： | 本文概述了在西藏高原长达450公里左右的南北向测线上取得九次湖中水下爆炸地震记录的处理结果。通过数字处理、拟合和反演等计算,得出了该地区地壳与上地幔的成层结构和速度分布。 结果表明,该区整个沉积岩层厚约3-5公里,雅鲁藏布江以北到当雄地带,地壳巨厚达70-73公里;江南地区为68-45公里,并逐渐向南翘起。在成层地壳介质中发现下地壳中存在低速层,厚约10公里,速度为5.64公里/秒。分析认为,高原地形与巨厚地壳的形成是印度洋板块与欧亚板块碰撞以及长期挤压和内部物质运移的结果。
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| 关 键 词： | 爆炸地震 当雄 西藏高原 测线 上地幔结构 地带地 首波 速度分布 雅鲁藏布江 地壳与上地幔 |
| 收稿时间： | 1980-02-01 |
EXPLOSION SEISMIC STUDY FOR VELOCITY DISTRIBUTION AND STRUCTURE OF THE CRUST AND UPPER MANTLE FROM DAMXUNG TO YADONG OF XIZANG PLATEAU |
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| Authors: | Institute of Geophysics Academia Sinica |
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| Abstract: | In order to study the layered structures and characteristics of the velocity distributions in the crust and upper mantle of the Xizang plateau region we have carried out explosions in the Lakes of Yarzhoyum, Pomu and Nam. Nine seismic records were obtained along a profile 430 km long in a nearly N-S direction.Six groups of phases of seismic waves through the crust and upper mantle in the area are observed which show different kinematic and dynamic properties.The result shows that the crust and upper mantle of Xizang plateau are stratified. Here the thickness of the sedimentary layer is from 4 to 5 km. The crustal structures along the two sides of Yarlung Zangbo river are different. The crustal thickness from the north of the river to Damxung region is from 70 to 73 km and the interfaces in the crust are essentially plane. Compared with that of the northern part, the crust of the southern part of the river is thinner. From the river to Yadong belt the crustal thickness is from 68 to 45 km. The crust of Xizang plateau consists also of high and low velocities layers. There is a low velocity layer in the lower crust and its thickness is 10 km, and its velocity 5.67 km/sec. A composite cross section and a model of the crust is given.The northern boundary of the collision zone of the two plates is quite clear cut and every layer in the crust is upwarping towards south. It shows that the formation of a thick crust and the uplift of the plateau are due to the results of a long period of compression, deformation, and crustal shortening by folding in a large scale. |
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