of the Tibet block relative to Golmud in the north and south directions is (9.3±4.6)mm/a, the strain velocity of the middle part in the west and east directions is (15.6±6.3)mm/a, reflecting the plateau lateral extruding movement. The Himalayan block is mainly compressing strain, and the middle part of the Tibet block is mainly extending strain. The highest extending and the compressing strain are 0.131×10−6/a and −0.189×10−6/a, respectively.

Global Positioning System (GPS) observations from three measurement campaigns from 1995 to 1999 are used in a study of the tectonic activity and earthquake hazards in North China. These GPS data were firstly processed together with about 13 Global IGS stations using the GAMIT software to get the baseline solutions, then crustal horizontal motion in ITRF97 frame and with respect to Eurasia were obtained based on these baseline solutions and their variance-covariance matrix using the GPS network adjustment software Power ADJ developed by Wuhan University. Using the GPS velocity field we estimate the annual accumulation of strain rate field and annual accumulation of density of strain energy field. These resulting fields show the following: (1) most stations move at a rate of (3-12mm/a)

We have determined approximate average rates of deformation in the Qinghai-Tibet plateau and its margins from the GPS data for last 10 years and the moment tensors from earthquakes between 1900 and 1999. We also determined the strain rate (seismic strain rate) associated with the seismic deformation using 254 Mw≥5.0 earthquakes, and estimated the shortening and extension rates for every block in the area as well. We also estimated the strain rate (geodetic strain rate) by 80 GPS sites' velocity vectors and analyzed characteristic of kinematics by two kinds of strain rates and discussed earthquake potential in the area. As a result, the deformation rates from seismic moment tensors and from GPS velocities are basically agreed with each other. It is feasi-ble to analyze seismic risk by comparing geodetic strain rate with seismic strain rate based on the opinion that strain energy will be released through earthquake. It is concluded that there is no strong earthquake potential (>M7) in the Qinghai Tibet plateau and its margins, but there is earthquake potential (>M5) in middle Tibet in a few years.

基于刚性块体和GPS稳定点组概念，用GPS稳定点组的水平速度值求出了各活动地块及华北亚板块的欧拉运动参数，推证了块体边界上的点相对运动速度矢量公式，通过该公式利用块体欧拉运动参数反演计算分析了地块边界带运动状况；通过块体欧拉运动参数反演计算各GPS观测点的背景运动速度，用观测点的实测运动速度减去各观测点的背景运动速度得出其实际变形值，进一步分析了各地块内部变形情况，并探讨了各活动地块的刚性特征。