Vertical surface displacement of mainland China from GPS using the multisurface function method

Abstract

The annual periodic deformation of Earth’s surface can be obtained indirectly using existing models. However, model reliability is affected by numerous uncertain factors such as indirect observation, inversion algorithms, and other factors. In this study, a model of annual vertical surface displacements of mainland China is built based on the direct observation of deformation by 234 continuous Global Positioning System (GPS) stations and unified data processing using the multisurface function method (referred to as the GPS model). The GPS model shows that the weighted root mean square (WRMS) is reduced for 97% of the GPS stations after applying the model correction. The average, maximum, and minimum reductions in the WRMS are 11.6%, 37.2%, and −3.6%, respectively. The slope of the fit lines are 0.40 and 0.61 for the GPS/SLM and GPS/GRACE annual periodic amplitudes, respectively, while a slope of 0.79 for GPS/GPS model from this paper, showing the advantage of GPS model in the representing of surface displacement. Additionally, the GPS model can accurately reflect the detailed motion characteristics of mainland China, particularly in areas between large and small hydrological changes. The difference between models and GPS observation in mainland China may be related to the leakage errors in the GRACE data processing and large uncertainty in the land water storage in SLM, indicating that GPS model may provide more realistic load estimates in mainland China. The GPS model can accurately describe the annual signal, which will be extremely important for practical applications and geoscience research in the future.