2013年4月20日芦山地震发生后,围绕芦山地震的发生是否与三峡水库、紫坪铺及瀑布沟等水库蓄水有关的争论较多。但定性的讨论难以给出一个确切的定论。本文拟从定量计算分析讨论三峡、紫坪铺和瀑布沟水库蓄水对芦山地震震源处弹性应力场和孔隙压力场的影响。计算结果初步表明,三峡、紫坪铺及瀑布沟水库蓄水引起芦山地震震源处的弹性应力变化仅为几十Pa;在低渗透系数(扩散系数小于1m²/s)时,3个水库蓄水造成的孔隙压力变化接近于0,对M_s^7.0芦山地震的发生几乎没有影响;当取高渗透扩散系数(10m²/s)时,只有瀑布沟水库蓄水引起震源处孔隙压力增加3.2kPa,库仑应力变化1.9kPa,然而连续延伸100km高渗透率断层基本不可能存在;在选取扩散系数1m²/s时,3个水库若均蓄水100a对M_s^7.0芦山地震震源处孔隙压力也仅仅达到kPa量级。研究结果表明,此次M_s^7.0芦山地震的发生与三峡、紫坪铺、瀑布沟等水库蓄水无关。

After the occurrence of the M_s7.0 Lushan earthquake on April 20, 2013, many media pointed that the occurrence of the Lushan earthquake was related with Three Gorges reservoir or Zipingpu reservoir or Pubugou reservoir, and so on. However, the qualitative arguments cannot give a reasonable conclusion. So, according to the previous studies, the analytic method is adopted to quantitatively analyse the impact of the Three Gorges reservoir, Pubugou reservoir and Zipingpu reservoir on the hypocenter of the M_s7.0 Lushan earthquake. The changes of elastic stresses and pore pressure of each reservoir to the M_s7.0 earthquake are calculated, respectively. The initial results indicated that the elastic stress changes induced by the Three Gorges or Pubugou or Zipingpu reservoirs are only dozens of Pa. When the diffusion coefficient is less than 1m²/s, the pore pressure changes of the hypocenter of the M_s7.0 Lushan earthquake are equal to zero, which means that the impoundment of the three reservoirs had no effect on the M_s7.0 Lushan earthquake. When there is a fault with a high permeability (diffusion coefficient is larger than 10m²/s) and extension of more than 100 km, the pore pressure changes of the hypocenter of the M_s7.0 earthquake could reach 3.2kPa and the coulomb stress change is 1.9 kPa. However, such a fault seems exceedingly unlikely. When a larger appropriate diffusion coefficient (1m²/s) is selected and 100 years filling of all the three reservoirs are supposed, the pore pressure and coulomb stress changes reached only several kPa. So, it can be confirmed that the impoundment of Three Gorges reservoir or Zipingpu reservoir or Pubugou reservoir is irrelevant to the occurrence of the M_s7.0 Lushan earthquake.