Simulating changes of gravity and Coulomb stress caused by the impoundment of the Baihetan hydropower station

The Baihetan hydropower station is the second largest hydropower station under construction in China. The changes of gravity and Coulomb stress caused by the impoundment process are very important for the study of water storage change and potential earthquake triggering in this area. This paper calculates the isostatic gravity anomaly field in the vicinity of the hydropower station reservoir area. The results show that the area is basically in an isostatic state and relatively stable. Then the elevation data of the Baihetan reservoir area is used to simulate the gravity changes caused by the impoundment process and Gravity Recovery and Climate Experiment Follow-on(GRACE-FO) satellite observations. Furthermore, the results are compared with GRACE-FO actual observation data. The simulation results show that the gravity changes caused by the impoundment are of a milligal magnitude, and the universal gravitation is the main cause of gravity changes in the impoundment process, which is two orders of magnitude greater than the elastic deformation result. The simulated GRACE-FO gravity changes show that the satellite observation gravity changes caused by the impoundment are of a microgal magnitude, and the GRACE-FO may observe the gravity changes of the impoundment of Baihetan hydropower station. Finally, the load theory is used to calculate the internal stress changes in the crust caused by the impoundment. The Coulomb stress changes of in the northern section of the Xiaojiang fault zone are calculated simultaneously. The result indicates that the Coulomb stress changes are greater than 0.01 MPa in the two areas south and north of Qiaojia. The possibility of triggering an earthquake in this area needs to be closely monitored.