Horizontal strain field in the Chinese mainland and its surrounding areas

In this paper, two kinds of equations of block elastic motion are established. One is the equation of rotation in the entire block and homogeneous, strain, and the other is the equation of rotation in the entire block and linear strain. Using the velocities of GPS sites located in the Western Region, Qinghai-Xizang and North China blocks, these two kinds of elastic motion equations and the rigid motion equation are tested statistically for their unbiasedness and validity to simulate the site velocities of the blocks. The results indicate that the equation with rotation in the entire block and linear strain is the optimal model to describe the block motion. Dividing the Chinese mainland into 10 blocks, the rotation and strain parameters of each block are estimated using the equation with rotation in the entire block and linear strain, and the velocities of GPS sites on the blocks. Then, the strain parameters of 1005 sites in the Chinese mainland and its surrounding areas are calculated with the spacing of P x P, and the strain field in Chinese mainland and the surrounding areas is obtained. The basic characteristics of the strain field are also analyzed. The direction of the principal, compressive strain obtained in the paper is well consistent with the principal compressive stress axes derived by the geological and seismological methods (except for South China block).