对水库诱发地震的两点认识

Some Thoughts on Reservoir-Induced Earthquakes

本文重点论述了水库诱发地震所具有的2个突出特点:①诱发地震的强度和频度均高于当地天然地震的正常水平,世界上已经发生的4次6级以上破坏性地震甚至发生在历史地震活动的空白区:②岩溶地区水库可能因库水位的快速上升而使溶洞中封闭部分气体产生气爆型水库诱发地震,但气爆型地震震级(M_L)仅为0.6,气爆震源只发生在浅地表处。三峡工程一期、二期蓄水诱发的地震群,其中M_L0.6级以上地震占74%,M_L1.0级以上地震占36%,震源深度在5—16km范围者占48%。M_L2.1级地震的震源机制解显示为四象限分布,显示系水库诱发的构造地震。这对我国西部大规模水电开发有重要的启示意义。

This paper discusses two characteristics of reservoir-induced earthquakes： 1） Both intensity and frequency of induced earthquakes are higher than that of the natural earthquakes in same region. For example, four induced earthquakes with M≥6.0 even occurred in the areas with very weak historical earthquake activity in the world; 2） The gas explosion in partial confined cave due to fast increase of water level in karst region may also result in induced earthquakes. However, the maximum magnitude of gas explosion induced earthquakes is only ME0.6, and gas explosion usually occurs in near surface of the ground （above 300m）. During the first and the second phase storages of water in the Three Gorges Project on Yangtze River, among more than 2000 micro earthquakes, up to 74% of quakes are with ML≥0.6 and 36% of quakes are with ML≥ 1.0. The depth of 48% quakes is in between 5-16km. Focal mechanism solution of the ML2.7 earthquakes shows the quadrantal distribution, which proves to be a typical example of reservoir-induced structural events.