Interpretation of Gravity Changes at the Dongchuan Station

High-precision time-varying terrestrial absolute gravity observations provide a powerful tool for investigating mass redistribution processes within the Earth’s interior and at its surface. The southeastern margin of the Tibetan Plateau is a tectonically active region with frequent strong earthquakes, making accurate interpretation of local gravity observations critically important for earthquake prevention and disaster mitigation. Based on four epochs of absolute gravity measurements acquired using FG5(X) gravimeters at the Dongchuan station from 2017 to 2022, combined with co-located continuous GNSS vertical deformation data, a GLDAS Noah Land Surface Model, high-resolution remote sensing imagery, and forward numerical modeling, we performed quantitative corrections for crustal deformation and hydrological effects and analyzed the residual gravity variations. The results show that gravity change at the Dongchuan station exhibited an overall increasing trend with a maximum amplitude of 8.2 μGal during 2017–2022. While the 2017–2019 gravity changes were consistent with the combined effect of crustal vertical deformation and hydrological loading within uncertainty, a positive residual anomaly of several microGal remained after 2019, which was attributed to mass redistribution caused by nearby anthropogenic activities. This study confirms that the 2017–2022 Dongchuan observations meet the requirements for milliGal-level static gravity field research, with the 2017–2019 data suitable for time-varying gravity studies, while the post-2019 data require that gravity variations induced by anthropogenic activities in the vicinity of the station be accounted for when applied to such studies. Additionally, time-series high-resolution remote sensing can effectively identify hundred-meter-scale gravity disturbance sources near observatories, providing valuable support for gravity data interpretation and quality control.