三峡水库诱发地震监测

Induced Earthquake Monttoring of the Three Gorges Reservoir

三峡工程于1993年开工，1997年11月8日大江截流，2009年9月15日启动175m试验性蓄水；2009年全部工程竣工投产。三峡水库已初步形成，全长660km，宽1．041．5km，总水域面积1048km2。随着蓄水位上升，库容及水域面积加大，发生水库诱发地震的可能性也将加大。根据最大历史地震震级并适当加权，确定库区最大可信地震为6级左右。在仙女山和九湾溪断裂一带（距坝址为18km）存在诱发地震的可能，震级Ms=5．0～5．8级。对坝址所受影响烈度为Ⅵ度，不会对按烈度Ⅶ度设防的枢纽主要建筑物构成直接威胁。三峡水库蓄水运行后，地震频次与强度虽有所增加，但地震活动仍保持在三峡地区原有弱地震活动本底状态。必须加强对三峡水库诱发地震的监测，预防地震及地质灾害，确保工程建设及运行安全。

The Three Gorges Project （TGP） has been commenced in 1993. The Yangtze main channel was closured on Nov. 8 1997. The experimental water storage to 175 m started on Sep. 15 2009, and the whole project was completed in the ending of 2009. The TGP reservoir is constructed for now with the length of 660kin, width of 1.0-1.5km, and the total area of 1048 km2. With the increase of water table, the reservoir capacity and water area are enlarged, and the possibility of induced earthquake increased. According to the magnitude records of historical maximum earthquake and properly weighted, it defined the maximum reliable earthquake of TG reservoir about ML6 magnitude, existed the probability of ML5.0-5.8 induced earthquake around the Xiannvshan and Jiuwanxi fault zone （18 km upstream of the dam）. However, the highest intensity around the dam site would not exceed Degree VI, whereas the main structures of TGP were designed with an anti-seismic intensity of Degree VII, hence the reservoir-induced earthquake would not form direct threat to TGP main structures. After the impoundment and operation of TG reservoir, the frequency and intensity of earthquake has been increased in some extent, yet the earthquake activities at TG region still kept in an original weak earthquake activities status. We should strengthen the TG reservoir induced earthquake monitoring and forecast, prevent the earthquake and geological calamity, ensure the safety of dam construction and operation, form the harmonious society as well as guarantee the long term security.