Ruzajkin, A. I.

The higher electrical conductivity of rocks in the middle and lower parts of the Earth's crust is generally related to the presence of fluids in rocks. The metamorphic processes of dehydration contribute to release of fluids, above all, water; these processes are also responsible for an increase in rock porosity and fracturing. These processes influence the stressed-strained state of the medium under specific conditions. A probable mechanism of earthquake source formation on the contact of blocks with different rates of dehydration and, consequently, different electrical conductivity is discussed. The spatial positions of electrically conductive and seismically active zones are correlated and definite relations between them are found with special reference to the vast area of the Northern Tien Shan within Kirgizstan and some other regions. The greatest concentration of earthquake sources is observed mainly near the contacts between blocks with contrastingly different electrical conductivity values and on sites with a sharp drop in conductive-layer depths.