Comprehensive Understanding of the Zipingpu Reservoir to the MS8.0 Wenchuan Earthquake

Abstract

AbstractSince the 12 May 2008 Wenchuan earthquake, whether this massive event was triggered by the impoundment of the nearby Zipingpu reservoir has attracted wide attention in international academic community. In addition to qualitative discussions, many scholars have made calculations on this issue. However, due to the different results, they draw very different conclusions. In this paper, we take the disputes from different teams in the quantitative calculation of Zipingpu reservoir as the starting point. Based on the basic principle of quantitative calculation of the stress changes after the impoundment of the reservoir, we analyze all kinds of influence factors to find out the key factors during the numerical simulation. The results show that the calculation methods, dimension of models, diffusion model, diffusion coefficient and focal mechanism are the main factors that resulted in the differences, especially the diffusion coefficient of the fractured rock mass. The Coulomb failure stress changes of the epicenter of the Wenchuan earthquake attained from the 2D model is about 3 times of that of the 3D model. And it is not reasonable that only considering the fault permeability or homogeneous isotropic rock mass permeability. The different focal mechanisms also could dramatically affect the Coulomb failure stress changes, of which the differences can research 2∼7 times. And the differences of Coulomb failure stress changes can reach several hundred times when selecting different diffusion coefficients. According to existing research that the magnitude of Coulomb failure stress change is about several kPa, we can not rule out the possibility that the Zipingpu reservoir may trigger the Wenchuan earthquake. However, for the background stress is not clear and Coulomb failure stress change is too small, we are not sure there must be a connection between the reservoir and earthquake. In the future work, we should target on the basis of field surveys and indoor experiments, improve the model and develop high‐performance simulation. Based on these calculation methods, we can compare more typical reservoir‐triggered earthquakes with different mechanisms both in China and elsewhere in the world to explore the mechanism of reservoir‐induced earthquakes.