ИСТИНА

Extensive seismicity data has been generated in the seismically active Koyna-Warna region of Maharashtra, India for the last five decades. Earthquakes continue to occur in the region since early 1960s when the initial construction and impoundment of the Koyna dam began. Several studies were done to explain triggered earthquakes based on seismicity and reservoir water levels, nucleation process, pore pressure changes, seismic and hydrological precursors. Comparative analysis was conducted for the dynamics of reservoir induced seismicity in this seismic area and for annual variations of the water level in reservoirs during the period of 1968-2012. The cyclic variations of water levels cause a cyclic response of seismicity in the seismic area between the Koyna and Warna reservoirs. Temporal changes of amplitudes of annual peaks of seismicity found to be not strong correlated with the water level variations. It is assumed that triggered seismicity in this region is caused by a combination of dynamic and kinetic factors, i.e. accumulation of stresses and water diffusion into the massive. Laboratory equipment and technique allow to model natural triggered seismicity by the initiation of acoustic activity in the loaded sample. The penetration of water from the surface of the sample into the inner part initiates acoustic emission swarms, which migrate to the area of increased stress and results in forming a macrocrack. The revealed features of temporal variations of parameters of the acoustic regime at the stages of excitation and decay of acoustic activity are qualitatively similar to those in the seismic regime. The work is supported by grant RSF-DST 16-047-02003.