Comprehensive Understanding of the Zipingpu Reservoir to the M_S8.0 Wenchuan Earthquake

Abstract

Since 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.

A Comprehensive Numerical Model for Reservoir-Induced Earthquake Risk Assessment

“…Our approach employs a two-dimensional model to simulate the alterations in elastic stress and fluid pore pressure caused by water loading. It is worth noting that the twodimensional model does magnify the calculation results, with values approximately two to four times higher than those of the three-dimensional model [19]. The limitation of the two-dimensional model lies in its consideration of changes in only two dimensions, effectively setting the third dimension to infinity.…”

“…Notably, the Aswan reservoir-triggered M L 5.7 earthquake in 1981 was assessed through finite element modeling, demonstrating increased pore pressure and Coulomb failure stress [14]. It is under debate whether the May 2008 Ms 8.0 Wenchuan earthquake and the abnormal seismicity prior to it were caused by the impoundment of the nearby Zipingpu Reservoir [15][16][17][18][19]. Tao et al [20] employed a three-dimensional numerical model to simulate the pore pressure and stress, proposing that the Zipingpu Reservoir's impoundment in China altered the regional tectonic stress field before the Wenchuan earthquake, although others think the link between the Zipingpu Reservoir and Entropy 2023, 25, 1383 2 of 10 the Wenchuan earthquake is low [18].…”

Influence of the Three Gorges Reservoir Impoundment on Xiannvshan Fault Activity

“…Ma et al [16] took fault activity as an earthquake-inducing factor and used the grey clustering method to predict and evaluate the reservoir earthquakes in the Three Gorges region of the Yangtze River. Cheng et al [17] studied the relationship between the Zipingpu reservoir and the Wenchuan earthquake by calculating the relevant characteristics of the fault under the reservoir impoundment. Shi and Cao [18] calculated the fault Coulomb stress state in the Longmen Mountain area by using the improved Coulomb stress calculation method and pointed out the shortcomings of the traditional calculation method.…”