中国大陆构造块体的现今活动和变形

在重新对 1998年和 2 0 0 0年的中国地壳运动观测网络基准站和基本站的 2期观测资料进行预处理的基础上 ,得到了ITRF97坐标框架下 ,参考时刻分别为 1998年 9月 5日和 2 0 0 0年 6月 8日 ,分布在全国各主要构造块体上的 79个GPS站的坐标和协方差矩阵。分别以中国岩石圈动力学地图集 (马杏垣 ,1989)中的中国大陆主要构造单元 (称之为亚板块 )和张培震等 ( 2 0 0 2 )给出的中国主要活动块体为格架 ,用笔者提出的 1种推广了的QUAD方法对中国大陆的 2 0个主要构造块体逐个进行判别检验。那些现今无明显相对运动的相邻块体则被归并起来 ,从而确定了活动块体和它们的边界。采用刚体运动 +块体均匀应变 +局部变形的模型作为描述中国大陆构造块体的现今活动和变形的模型。求出了有明显相对运动块体的欧拉运动矢量和块体的整体均匀变形参数、各块体内部的不均匀局部变形以及活动边界的活动方式和强度。在此基础上 ,除了一般地指出中国大陆地壳运动西强东弱的特征之外 ,还对西部主要活动块体和边界活动强弱给出了定量比较结果 ,从而为强震危险区的判别提供了形变背景依据

PRESENT-DAY ACTIVITY AND DEFORMATION OF TECTONIC BLOCKS IN CHINA S CONTINENT

On the basis of carefully pre-processed GPS data observed at reference and basic stations of CMONOC (Crustal Movement Observational Network Of China) in 1998 and 2000, the coordinates in ITRF97 referenced to the epochs of 1998.6808 and 2000.4658 as well as their covariance matrices at 79 GPS stations distributed in the main tectonic blocks over China's continent are derived respectively. Under the tectonic framework of the main tectonic units and the main active blocks of China proposed by MA Xing-yuan et al. and ZHANG Pei-zhen et al., respectively, 20 major tectonic blocks in China's continent are tested and identified one by one by using an extended QUAD (Quasi-Accurate Detection of gross errors) method (HUANG Li-ren, et al., 2002). The adjacent blocks with no significant relative motions to each other are merged into one block. Thereby, the active blocks and their boundaries are identified. A model combining the rigid motion, block uniform strain and local deformation is used to describe the present-day activity and deformation of tectonic blocks in China's continent. The Euler's vector and the entire uniform deformation parameters of the blocks with significant relative motion, as well as the local heterogeneous deformation within the blocks are derived. The pattern and rate of motion on active boundaries are also calculated. Based on the afore-mentioned results, it is pointed out that the crustal motion in China's continent is much stronger in the western part than in the eastern part. In addition, the quantitative comparisons of crustal motion among the main active blocks and boundaries in the western part of China are also given. This result may provide the deformation background for the evaluation of earthquake risk regions.