Investigating crustal vertical deformation in the Sichuan-Yunnan region using GNSS and environmental loading models

Abstract To obtain the vertical component of crustal tectonic movement in the Sichuan-Yunnan region, non-tectonic deformations induced by environmental loading and common mode errors must be removed from GNSS vertical displacements. Based on GNSS data and corresponding Hydrological Loading (HYDL) deformation data from 48 continuous stations in the Sichuan-Yunnan region from January 2012 to June 2023, this study systematically analyzes the quantitative relationship and temporal variation characteristics between GNSS vertical displacements and HYDL deformation. Additionally, wavelet analysis is employed to investigate the time-frequency periodic characteristics of both time series. The results indicate that the average correlation coefficient between GNSS vertical displacements and HYDL deformation is 0.62. After removing the HYDL deformation from the GNSS vertical displacements, the root mean square (RMS) decreases by an average of 33.98 %. Wavelet analysis further reveals that most stations exhibit consistent variations at the annual cycle scale, demonstrating that HYDL deformation is a crucial controlling factor for the annual variations in GNSS. The vertical velocity field obtained after correcting for both hydrological loading and common mode errors indicates that the entire Sichuan-Yunnan region is generally uplifting at a rate of 0.16–2.41 mm/a. These findings demonstrate that environmental loading correction is of significant importance for recovering the true vertical tectonic deformation in the Sichuan-Yunnan region, providing a reliable basis for high-precision monitoring of regional vertical crustal movements.