【作者】 滕吉文； 熊绍柏； 尹周勋； 徐忠信； 王香泾； 卢德源；

【Author】 Teng Jiwen Xiong Shaobai Yin Zhouxun (Institute of Geophysics,Chinese Academy of Sciences) Xu Zhongxin Wang Xiangjing (Changchun Geological Institute of China,Changchun,China) Lu Deyuan (Geological Academy of Sciences,Ministry of Geology,Beijing,China)

【机构】 中国科学院地球物理研究所； 长春地质学院； 地质矿产部地质科学院；

【摘要】 为了研究喜马拉雅山脉地区地壳与上地幔的结构和速度分布特征,在西藏高原南部的普莫错和佩古错以湖中水下爆炸、在定结以井中爆炸激发地震波.在普莫错到佩古错长约475 km的近东西向剖面上进行了深部地震探测.经过数据处理和反演计算,发现该区存在六组反射波:t₁、t₂、t₃、t₄、t₅和t₆.这些波分别具有不同的运动学特征,并得到:（1）喜马拉雅山北部地区地壳为成层结构,地壳中存在着低速层,其厚约10 km,层速度为5.6—5.7 km/s.这表明,西藏高原的地热分布及其活动是由于高温地壳介质中存在着熔融或部分熔融.（2）地壳结构和速度分布在横向上是不均匀的,喜马拉雅山北部地带地壳厚度为73-75km,其速度为6.2—6.3 km/s.在特提斯喜马拉雅地带地壳变形强烈.（3）根据射线追踪、理论地震图和反射波震相的识别给出了喜马拉雅山北部地壳-上地幔的初步模型.巨厚地壳的形成是由于印度板块与欧亚板块相碰撞的结果,在此期间地壳中存在着大规模的水平皱缩.此项工作是由中国和法国地球物理学家于1981—1982年共同完成的.更多还原

【Abstract】 In order to study the layered structure and characteristics of the velocity distributions in the crust and upper mantle of the northern part of the Himalayas,we have made detonations in Puma Lake,Peiku Lake,and the Dinggye region.Four seismic record sections were obtained along a 475 km long profile in a nearly E-W direction from Puma Lake to Peiku Lake. Accordingto dataprocessing andinversion,6groups,t₁,t₂,t₃,t₄,t₅,t₆ of reflected phases throuth the crust and upper mantle in the area are obtained.They show different kinematic and dynamic properties.The results of data analysis are as follows: （1） The crust is multilayered and there exists a low velocity layer in the crust.The thickness of the low velocity layer is about few kilometers,and with a layer velocity of 5.6-5.7 km/ s.This indicates that the cause of geothermal distribution and its activity in the Xizang plateau is due to the high temperature in the crustal medium and the existence of melting or partial melting matter in the crust. （2）Structure and velocity of thick crust are horizontally inhomogeneous.The crustal thickness for the north Himalayas is 73-75 km and its velocity,6.2-6.3 km/s.Crustal deformation is very strong in the Tethys Himalaya region. （3）On the basis of results from ray tracing,theoretical seismogram,and phases of reflection waves,a preliminary model of crust and upper mantle in the northern part of the Himalayas is put forward. The extremely thick crust was caused by the result of the collision of the Indian plate against the Eurasian plate.During the process of continuous pressing the horizontal shortening took place on a large scale in the crust.更多还原