Surface seasonal mass changes and vertical crustal deformation in North China from GPS and GRACE measurements

Abstract

The Earth is an elastic body, and the surface mass loading changes will lead to elastic loading deformation on the surface of the Earth. In this study, we investigated the surface seasonal mass changes and vertical crustal deformation in North China using the data obtained by the techniques of the Global Positioning System (GPS), Gravity Recovery and Climate Experiment (GRACE) and Surface Loading Models (SLMs). The seasonal annual signal and semi-annual signal obtained by the three techniques show strong correlations. The average value of the weighted root-mean-square (WRMS) of the all 30 sites is 58% after deducting the GRACE-obtained vertical deformation from the GPS-derived vertical deformation. However, the consistency of results between GPS and SLMs is not so good, with a 31% mean WRMS reduction, due to the fact that the global SLMs perform not well in North China. The GRACE-measured long-term trend is deducted from the GPS-obtained vertical rates to reveal the crustal displacement caused by the underground factors such as tectonic movement and groundwater in North China. The results show that the rates of stations HECX and TJBH are very large, more than 10 mm/yr, which suggests that the surface subsidence is caused by excessive exploitation of groundwater.