Studies of tectonic destruction of rocks, with lithostatic pressure taken into account, reveal several stages or geotectonic levels of crustal stratification differing in the geometric parameters of fissuring and permeability. The most favorable geological and hydrogeological conditions appear for the formation of earthquake foci at the margins of the downwarping zone, especially in the initial stage of filling of a reservoir. This is confirmed by the fact that most earthquake foci are associated with the marginal sectors of the downwarping zone. Oscillatory motions of the crust caused by the cyclic effect of a water load during reservoir operation cause a periodic burst of seismic activity both at the downwarping periphery and under the reservoir due to the formation of dilatation zones in the crust. The change in the mechanical properties of the medium, especially a decrease in its strength as a result of filling and operation of the reservoir, leads to a premature destruction of rocks and the forming of small focus earthquakes.
USSR Report Earth Sciences JPRS UES
- Pub Date:
- July 1984
- Structural Properties (Geology);
- Water Pressure;
- Earth Crust;