Surface gravity and deformation effects of water storage changes in China's Three Gorges Reservoir constrained by modeled results and in situ measurements

摘要

The water impoundment of China's Three Gorges Reservoir (TGR), with the largest dam in the world, makes a large mass concentrated and thus influences the surface gravity field and crustal deformation field. In the TGR area, water impoundment began in 2003, and the Earth is responding to the ongoing changes of water storage. These responses can be investigated using the gravimeter and the GPS. In this paper, using a water load model derived from Digital Elevation Model (DEM) data and elastic loading Green's function, we modeled the surface gravity and displacement changes in the front area of TGR caused by water storage variations. Predictive results are compared with the measurements derived from absolute gravity by A10, continuous gravity by gPhone and GPS time series at the sites of front area in TGR. The observations agree well with the prediction spatially and temporally. The quantitative comparison and analysis indicate that the ground gravity and the vertical displacement are more sensitive to water storage changes than the horizontal displacement. The predictions from the water load model are consistent with the in situ measurements reported in this work and therefore can be utilized for water effect corrections for exacting the further signals related to lithospheric dynamics and geological hazards, such as abnormal deformation of active faults and landslides.