Surface vertical displacements and level plane changes in the front reservoir area caused by filling the Three Gorges Reservoir

摘要

On the basis of the results of geological surveys and seismic prospecting in the Three Gorges area, two Earth models are constructed which are appropriate to the crustal structure in the front Three Gorges Reservoir area. Utilizing load-induced deformation theory, we model the surface vertical displacements and level plane changes in the area caused by increased water loads of the reservoir. The two quantities are needed to determine height changes on the Earth's surface. The numerical results demonstrate that the heights will be significantly changed as the reservoir fills up. For example, when the reservoir water level reaches an elevation of 175 m, the crust subsides by 1.0 similar to 48.3 mm, the level plane uplifts by 1.1 similar to 7.5 mm, and the height falls by 2.1 similar to 45.0 mm. Accordingly, our results provide the reliable corrected values for discriminating between the earthquake-related crustal motion and the height changes that occur due to reservoir impoundment. Moreover, if the height data previously observed in the area need to be used for engineering surveys after the reservoir is filled, they must be corrected. [References: 14]