Analysis of Three-Dimensional Seasonal deformation induced by GPS and loading models in Yunnan, China

Seasonal deformation related to mass redistribution on the Earth’s surface can be recorded by continuous global positioning system (GPS) and simulated by surface loading models. In this study, we compared the three-dimensional seasonal deformation from 27 continuous GPS stations and surface loading models in Yunan, China. A good consistency of vertical seasonal variations can be observed between GPS and loading models, while obvious discrepancies exist in the horizontal seasonal deformation between them, especially for the East component. The reduction ratios of the median amplitudes of GPS annual variations obtained with loading corrections are 39.37%，-18.01% and 56.39% for the North, East and Up components respectively. We found that the significant difference in horizontal annual deformation between GPS and loading models is primarily attributed to the discrepancies of GPS annual phases at different stations. Seasonal vectors are employed to discriminate loading at different spatial scales. The results suggests that the large-scale load is concentrated in the southwest of Yunnan, the disordered horizontal annual phase may be related to local-scale mass loading. In addition, after removing the loading deformation from GPS time series, GPS vertical velocity uncertainties are significantly reduced, with the mean reduction ratio about 9%.