Effects of crustal interface variations in Three Gorges area on vertical deformation due to impoundment events

摘要

On the basis of the results of geological survey and seismic prospecting in the Three Gorges area, the elastic earth model is constructed with lateral heterogeneities in the depths of crusal interfaces, which is more appropriate to the realistic crustal structure than a laterally homogeneous one. The finite element method is used to simulate the surface vertical deformation caused by increased water loads of the reservoir associated with the filling events for the two types of models. The numerical results show that the differences for the two models are large enough to be resolved by modern geodetic measurements. For example, for homogeneous earth model when the water level is 135m high (filling event in 2003), the largest vertical displacement is 27.7mm. However, for heterogeneities model the largest vertical displacement is 24.6mm. The difference is as large as 3.1 mm. This demonstrates that the effects of lateral heterogeneities in the depths of crustal interfaces should not be neglected but must be considered in the future study of loading process in the area.