Current crustal motion and deformation in the Chinese mainland and its surrounding area determined from GPS data

Based on the geodetic data taken from the National GPS Network established by China Climbing Program “Investigation of Crust Motion and Geodynamics in Modern Time”, we derived the movement velocities of the GPS sites. In terms of the power series expansion of a rotation function for horizontal velocities on a spherical surface proposed by Haines and Holt (1993), we computed the horizontal velocity and strain-rate field. We preliminarily studied the appearances and characteristics of the present-day crustal movement and deformation in the Chinese mainland with the computed results. The researches demonstrated: (1) The present-day crustal movement and deformation in the Chinese mainland are being jointly controlled by Indian, Pacific and Philippines Ocean Plates and Siberia-Mongolia block, and these three large plates and block form a situation of tripartite confrontation, but Indian Plate seems to play a leading role; (2) The North-South Earthquake Zone plays an important adjustment role in the present-day crustal movement and deformation process, displaying clear characteristics of demarcation line of tectonics in large areas; (3) There seems to be another adjustment zone along the latitude line approximate N35°, but its characteristics are less obvious than that of the former; (4) Dynamic actions of these three large plates and block on the Chinese mainland are dynamic stable; appearing in stable push-press velocities. These results are generally accorded with the results determined from geology, geophysics, and seismology. By the contrast with seismicities, it appears preliminarily that there is some corresponding relation between intense shear strain zone and future strong seismicity area, but this problem needs further examination of earthquake examples.