Identification and elimination of non-tectonic crustal deformation caused by land water from GPS time series in the western Yunnan province based on GRACE observations

Based on the data of 13 continuous GPS stations in the western Yunnan province, China, from Crustal Movement Observation Network of China (CMONOC) and the GRACE time-varying gravity field data from Space Geodesy Research Group (GRGS), France, we analyzed the magnitude and characteristics of the non-tectonic crustal deformation variation induced by land water migration in western Yunnan, and discussed the theoretical foundation and model for eliminating the non-tectonic deformation from GPS time series. The result shows that the non-tectonic crustal deformation fluctuation with an annual period in the vertical component of GPS time series is significant in this area, with the maximum as large as 12mm, and about 42% of the fluctuation is from the crustal deformation induced by land water migration. By using the method of Principal Component Analysis (PCA), we got the common mode error (CME) of the GPS network, which correlated with the GRACE land water loading deformation with a coefficient of about 0. 87. When the land water loading deformation is used to correct the GPS error, the root mean square (RMS) of GPS common mode error will reduce by 64%. Therefore, a significant part of GPS common mode error in this area can be eliminated explicitly based on the GRACE time-varying gravity field. However, since GRACE can only effectively detect the overall land water loading deformation with a scope of 400km now, more detailed and specific non-tectonic deformation of individual GPS station is still out of the reach of GRACE.