Time-varying gravity field model of Sichuan-Yunnan region based on the equivalent mass source model

High-precision time-varying gravity field is an effective way to study the internal mass movement and understanding the spatio-temporal evolution process of the geodynamic system. Compared to the satellite gravity measurement, the repeated terrestrial gravity observation can provide a more high-order signal related to the shallow crust and subsurface. However, the suitable and unified method for gravity model estimation is a key problem for further applications. In this study, we introduce the spherical hexahedron element to simulate the field source mass and forward model the change of gravity field located at the Sichuan-Yunnan region (99–104°E, 23–29°N) in the four epochs from 2015 to 2017. Compared to the experimental results based on Slepian or spherical harmonics frequency domain method, this alternative approach is suitable for constructing the equivalent mass source model of regional-scale gravity data, by introducing the first-order smooth prior condition of gravity time-varying signal to suppress the high-frequency component of the signal. The results can provide a higher spatial resolution reference for regional gravity field modeling in the Sichuan-Yunnan region.