喜玛拉雅“东构造结”地区特异重力场的探讨  

Specific gravity field of the 'Himalayas east structural knot'

作　　者：王谦身[1] 滕吉文[1] 王光杰[1] 徐亚[1] 张雪梅[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029

出　　处：《地球物理学进展》2007年第1期35-42,共8页Progress in Geophysics

基　　金：国家自然科学基金项目(40434009)资助

摘　　要：跨越中、印、缅三国交界的青藏高原东南的喜玛拉雅“东构造结”地区(92°E^97°E,26°N^30°N)一半以上的面积尚没有重力测点,是重力数据空白区,故无法直接研究其重力场特征与深部地壳结构(构造).本文分析了卫星重力异常的特性,提出应用卫星重力异常作为近似空间重力异常,并作布格改正后,得到的布格重力异常具有与该地区地形高程呈镜像相关的特征,可用以研究深部地壳结构.据三条重力剖面计算得到该地区三个地壳深部结构剖面的结果,给出青藏高原地壳厚度>70 km;喜马拉雅造山带为55 km左右;布拉马普特拉河谷盆地为33~35 km;那加山山脉地区为40~45 km,显示出三者为三个不同的构造单元.同时给出布拉马普特拉构造单元为相对高密度的刚性物质构成,随着印度洋板块向北运移,在碰撞、挤压下,插入青藏高原东南缘一带.导致该地带的强烈构造运动,和频发大、小地震.最后提出了几点认识和建议.More than half of the ＂Himalayas east structural knot＂ area （92°E-97°E, 26°N-30°N） that stretch cross boundaries of China, India and Burma has no ground gravity measuring point yet. Here it is hard to research directly the gravity field characteristic and the deep crustal structure. In this paper, the satellite gravity anomaly data are employed as pseudo free air gravity anomaly to calculate Bouguer gravity anomaly. The calculated Bouguer gravity anomaly exhibits well mirror correlation with the topography altitude of this district. It can be used to research the deep crustal structure. Three profiles of deep crust structure according to three Bouguer gravity anomaly profiles are obtained. In Tibetan plateau the crust thickness is more than 70 km, in orogenic belt of Himalayan mountains it is about 55 km of, in Brahmaputra basin valley it is 33 to 35 km, and in Naga mountain it is 40 to 45 km. Three tectonic units are displayed. The Brahmaputra tectonic unit in ＂east structural knot＂ is composed of high-density matter, moves northward after collision and extrusion by Indian Ocean plate, and then inserts into east margin of Tibetan plateau. This dynamic process results in violent tectonic movement of southeast and northeast edges of Tibetan plateau, in- duces a series of earthquakes frequently. At last, some conclusions are advanced.

关 键 词：喜玛拉雅 东构造结 重力场 深部地壳结构 

分 类 号：P312[天文地球—固体地球物理学]