Effectof Seasonal Changesin Water Level in Chirkey Reservoir on the Apparent ResistivityofRocks Kadomskogo Dome, Located in its Vicinity

Abstract

Relevance. The nature of the occurrence of technogenic seismicity in the areas of large reservoirs remains poorly studied due to the lack of new geophysical experimental data, except for seismological ones. At the same time, large-scale long-term monitoring in HPP areas allows us to study the mechanism of the reservoir’s impact on the environment. One of these experiments was conducted in the area of the Chirkeysky reservoir, located in the North Caucasus, for 9.5 years from 1998 to 2007 using the method of dipole electric sensing. Aim. The purpose of this work is to study the geodynamic process of rocks in the area of a large reservoir caused by seasonal fluctuations in its level. Methods. To measure the apparent electrical resistance of a large rock mass, the method of deep dipole electric sounding at a constant current with a measuring dipole distance of 5.6 km was used. Probing was conducted daily. The equipment, a digital receiving station and a 25 kW generator were specially designed for this purpose. Result. As a result of the analysis of the relationship between the data series of the apparent electrical resistance of a large rock mass located in the Northern vicinity of the Chirkeyskaya HPP and seasonal changes in the water level in the reservoir, a connection was established with the period of the maximum rate of filling of the reservoir. The mechanism of seasonal variations in apparent resistance is due to the deformation of rocks under the influence of changing reservoir load. The process of deformation of vertical crack zones located between the dipoles of the measuring unit leads to a change in their conductivity, thereby causing the effect of “shielding” the field of the feeding dipole from the location of the receiving dipole in the studied array. The obtained data show the impact of changes in the seasonal load of the Chirkei reservoir on the environment, activating the manifestation of dangerous geological processes in the reservoir area, the collapse of unstable rock massifs, landslides.