【摘要】 迄今为止,长江三峡库首区蓄水对上地壳构造应力场影响的数值模拟研究中存在的最大问题是未考虑地形“峡谷效应”和库水下渗导致“岩石弱化”的影响。利用高精度DEM图和135 m水位蓄水同期重力异常观测资料,首次建立包含地形单元、库水下渗因素等复杂条件下的三峡库首区上地壳三维数值模型。在Marc软件平台上,以优选加载方案进行数值模拟,揭示135 m水位、175 m水位蓄水条件下库首区上地壳构造应力场的动态变化,发现九湾溪、马鹿池、官渡口、牛口等断裂带挟持区出现最大3.5～5.0 MPa的最大主应力降等有利于高角度正断层失稳的应力场变化,预测175 m水位蓄水影响将呈“继承性”发展。首次提出“二次诱发地震”、“水库诱发地震潜在震源”、“叠加潜在震源”的思想,探讨了蓄水对秭归、巴东2个重点区域断裂稳定性、孕震环境及地震危险性的影响。更多还原

【Abstract】 The main problem on simulation of tectonic stress field after reservoir impounding in the head area of the Three Gorges is the influence of“canyon effect” and “rock soften.” For the first time,taking the terrain,water load distribution,infiltration range and the fault units into account,the 3D numerical modeling of the upper crust of the Head Area of the Three Gorges is established on the software platform of Marc to reflect the change of tectonic stress field under the load cases—water lever 175 m and 135 m.From the numerical simulation results,it is discovered that under water level 135 mt,he maximum principal stress descends(3.5-5.0 MPa) is connected with the activities of high angle normal fault and these changes are more obvious under water level 175 m.The idea of“secondary induced earthquake”,“potential induced seismic source in reservoir”and “superposition seismic source”are presented first.Moreover,the effects on the stability of area fault and the seismogenic environment in Zhigui and Badong after impoundment are analyzed.更多还原