Horizontal Strain Field in Chinese Mainland and the Surrounding Areas

AbstractIn the paper, two kinds of equations of block elastic motion are established: the equation with rotation in the entire block and homogeneous strain and the equation with 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, both the elastic motion equations and the rigid motion equation are tested statistically for their unbiasedness and validity to simulate the site velocity of the block. The tested results indicate that the equation with rotation in the entire block and linear strain is the optimal model to describe the block motion; the equation with rotation in the entire block and homogeneous strain ranks the second; and the model of the block rigid rotation is the third. 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 points in Chinese mainland and the surrounding areas are calculated with the spacing of 1° × 1°, and the strain field in Chinese mainland and the surrounding areas has been obtained. The basic characteristics of strain field in Chinese mainland and the surrounding areas are also analyzed in the paper. The direction of the principal compressive strain obtained by the method in the paper is well consistent with the principal compressive stress axes derived by the geological and seismological methods (except for South China block). The strain field has a very close relation with the main fault zones, and all the main fault zones of the block boundaries are the gradient zones with high‐level first shear strain rate. The fault zone is the result from the adjustment of strain‐stress field.