中国大陆现今地壳水平运动基本特征

GENERAL CHARACTERISTICS OF THE RECENT HORIZONTAL CRUSTAL MOVEMENT IN CHINESE MAINLAND

介绍利用中国地壳运动观测网络基本网、基准网 1 998年和 2 0 0 0年 GPS观测结果所获得的中国大陆地壳水平运动信息 .简要介绍这两次 GPS观测概况 ,以及用 GAMIT/GLOBK软件对所获得 GPS观测数据的处理及精度分析 .基准网与基本网各年观测结果得到的网内点位精度、水平分量精度平均为 2 mm左右 ,高程分量精度平均为 5 mm左右 ,由两期观测得到的水平位移分量的精度平均为 3 mm左右 .得到的 1 998年 9月初至 2 0 0 0年 6月中旬基本网、基准网中的地壳运动 ,包括以位于东部的一组稳定点为基准的各观测站位移、网内各部分的应变及部分地区的旋转量 .根据所获得的我国大陆较为完整而详细的地壳水平运动图象 ,分析了中国大陆现今地壳运动的主要特征 .在所述观测期间 ,我国东部地区变形较小 ,相对较为稳定 .相对位于东部的稳定点组 ,东北块体向北运动 ,位移量约 1 0 mm;华南块体向东南运动 ,位移量约 9mm.相对东部地区 ,西北部新疆地区以北西向运动为主 ,位移量约 2 6 mm;西南西藏地区以向北运动为主 ,位移量约3 2 mm;西藏东部与云南地区形成非常明显的顺时针旋转构造运动 ,旋转中心位于 2 6 .5°N,95 .5°E,旋转量为 0 .0 0 4 5″,旋转位移平均为 1 2 mm左右 .我国中部南北地震带是一强烈而复杂的变形带 .

In this paper, the horizontal crustal movement obtained from GPS observations in 1998 and 2000 at basic and fiducial stations in the Crustal Movement Observation Network of China (CMONOC) is introduced. A brief introduction of the field observations, the data processing with GAMIT/GLOBK software and the accuracy of the GPS observations are given. In average the accuracy of the results for each year is about 2 mm in the horizontal components and 5 mm in the vertical component, and the average accuracy of horizontal displacements at a station is about 3 mm.The results of crustal movement during the period from early September 1998 to mid June, 2000, including the displacements at each station with datum definition of a group of stable stations of insignificant relative movements among themselves in the eastern part of China, strains in different parts of the network and rotations in some parts, are obtained. Based on the crustal movement maps which are more complete and detailed than previous ones, the general characteristics of the recent crustal movement in Chinese mainland are discussed. During the above mentioned period of observations, the crustal deformation in the eastern part of China was relatively small and quite stable. With reference to a group of stable stations with small relative movement in the eastern part of China, the northeastern China block moved northward for about 10 mm, the southeastern China block moved southeastward for about 9 mm. With reference to the eastern part of China, the northwestern part of China moved northward for about 26 mm, the Tibetan area in southwestern part of China moved mainly northward for about 32 mm. The area in Yunnan and east Tibet showed significant clockwise tectonic rotation of 0.0045″ or average rotational displacement of 12 mm with the rotation center at N26.5° and E95.5°. The North south seismic belt in the middle part of China is a belt of active and complicated deformation. The observation results show that the northward pushing by the Indian plate has still played the dominant role in the crustal movement in Chinese mainland.