Deformation in the Three Gorges Reservoir after the first impoundment determined by GPS measurements

Abstract A 6 year long GPS observation (1998—2003) indicates that crustal deformation in the Three Gorges area is less active at a marginally measurable rate of 0—5 mm/a relative to stable South China block. However, the impounding water in June 2003 has induced transient displacement at the Three Gorges dam and the emerging reservoir. GPS measurements after the first stage of water filling of the reservoir demonstrate that vertical subsidence close by the impoundment is located in the segment of the reservoir from Maoping to Xiangxi. The water loading-inducted deformation dimishes rapidly with the distance from banks of the reservoir. The overall pattern of transient deformation is consistent with the simulation result of Farrell, and is attributed to the elastic response of upper lithosphere crust to overlying water reservoir. ∗Supported by National Natural Sciences Foundation of China (Grant Nos.40274007 and 40304002), Seismological Union Fund of Chinese Seismological Bureau (103030, 602015), the Minis...