On the Improvement of Mass Load Inversion With GNSS Horizontal Deformation: A Synthetic Study in Central China

We carry out synthetic experiments of mass load inversion using Global Navigation Satellite System (GNSS) vertical and horizontal displacements in Central China. Using two synthetic mass load models from a checkerboard mass distribution and a more realistic distribution derived from the Gravity Recovery and Climate Experiment (GRACE) observations, the inverted mass changes are determined based on the load theory and then compared with the known mass‐change inputs. We find that the combination of horizontal displacements with the commonly used vertical displacements significantly improves the inversion results when the number of sites is larger than one third of the number of total grids with relatively uniform distribution over the region. Synthetic tests demonstrate that data from the Crustal Movement Observation Network of China, including the total number of GNSS sites, spatial distribution, and precision, are sufficient to infer the annual amplitudes of mass changes in the region with comparable spatial resolution as that of GRACE observations. For the current precision level of the GNSS surface displacements (3.0 mm in the vertical and 1.0 mm in the horizontal components), including horizontal displacements leads to ∼10% improvement in mass inversion, compared to using vertical displacements only. With a higher precision level of 0.50 and 0.17 mm (for vertical and horizontal components, respectively), an improvement of ∼20% can be achieved. Plain Language Summary The Earth's surface deforms due to the pressure variations (mass load changes) from above, such as atmosphere, ocean and land water, and this deformation can be measured by the Global Navigation Satellite System (GNSS) technique. Based on a series of formulae (called mass load theory), which describe the relationship between the Earth's surface deformation and mass load, the mass load changes can be inferred by the surface deformation from GNSS measurements. The GNSS‐observed surface displacements in the vertical direction are widely used to estimate the mass changes, because of the larger signal amplitude compared to that in the horizontal directions. In order to analyze the potential contribution of horizontal deformation to the mass inversion, we do simulative tests using modeled mass changes and surface deformation, and find that the improvement by including the horizontal deformation can reach ∼10% under the current precision of GNSS measurements over the region of Central China. Through