Detection of Changes of the Earth's Volume and Geometry by Using GPS and VLBI Data

Based on the coordinates, velocities and their error estimations of GPS and VLBI stations in 2003, using Delaunay arithmetic to form series of triangles to approach the surface of the Earth, the Earth's area, volume and their changes were studied. And using stations through plate motion model interpolation, the feasibility of this detection method was verified. The results show that geodetic and interpolated data give the consistent conclusion: if taking the equator as the boundary, the northern hemisphere of the Earth is undergoing compressive deformation, and the southern hemisphere is undergoing extensional deformation; If taking the longitude line of 0° – 180° as the boundary, the east hemisphere is undergoing compressive deformation, while the west hemisphere is extended; If taking the longitude line of 90° – 270° as the boundary, the Pacific hemisphere is undergoing compressive deformation, and the Atlantic hemisphere is undergoing extensional deformation. The deformation patterns indicate that the Earth is still undergoing asymmetrical deformation. Based on the combined data of GPS and VLBI, we calculated the rate of volume changing to be up to –1.5937×10 12 m 3 ·a −1 , corresponding to the Earth radius decreasing by 3~4mm every year, which indicates that the Earth is undergoing compressive deformation as a whole.