The characteristics of the vertical deflection in the Chinese mainland using GRACE time-varying gravity field

The deflection of the vertical (DOV) reflects the discrepancy between the Earth's actual gravity field and reference models (e.g., WGS84, GRS80). The Chinese mainland exhibits highly complex topography and geomorphology, active crustal deformation, and pronounced spatial heterogeneity in the gravity field, creating an urgent need for large-scale, high-precision analyses of DOV to deepen understanding of regional gravity-field characteristics. We utilize long-term GRACE satellite data, together with the XGM_2019e static gravity model and GRACE RL06 time-varying data, to compute the meridional and prime-vertical components of the DOV (including the contribution of water mass variations) for the period 2002 to 2016 at 3328 grid points across the Chinese mainland. The results show larger DOV variations in western China (±10″) and smaller variations in the eastern region (0–5″), with opposite trends in the meridional and prime vertical components in the east. Three regions with anomalous DOV variations were identified: the Ordos-Taihang Mountains, the Sichuan-Yunnan region, and the Yadong-Gulu fault zone. By constructing an absolute DOV model and comparing it with the GPS velocity field in the corresponding region, the relationships among DOV, geoid morphology, and regional tectonic motions are revealed.