The article presents the methods and results of the magnetotelluric sounding within the Avacha-Koryaksky group of volcanoes. Geoelectrical section was studied within the period range from 0.0001 to 1000 seconds and above. The authors performed a numerical two-dimensional modeling. Initially, we used test models for possible distortions of curves. The analysis of the magnetotelluric parametres allowed us to characterize the geoelectrical inhomogenuities. Curves along the strike and across the strike were used as main curves. Since longitudinal curves are less prone to coast effect, they were used with transverse curves in order to create a geoelectrical model based on a 2D magnetotelluric field numerical modeling. The created geolectrical model has a conductive bed in the upper part of the section that is connected with an igneous-sedimentary cover. The deep part of the model includes near-vertical conductive zones, which denote a zone with deep faults. The paper describes possible nature of the revealed anomalies and provides rough estimation of rock porosity in the conductive zones.

A velocity structure of the lithosphere has been determined in the junction area of the Kuril-Kamchatka and Aleutian island arcs based on travel times of compressional (P) and shear (S) waves excited by regional and volcanotectonic earthquakes using the algorithm of successive anomaly subtraction. We describe deep-seated velocity heterogeneities at different depths in the lithosphere, their relation to tectonics and to seismicity. It is shown that the deep-seated source of magma supply for the Klyuchevskoi volcanic cluster is confined to a junction of deep-seated mantle faults (in map view this occurs at the location where the Kamchatka R. streambed turns eastward). The heterogeneity in question probably has asthenospheric roots. The crustal velocity structure beneath Klyuchevskoi Volcano together with data provided by other geological and geophysical methods (deep seismic sounding, electromagnetic methods, lineament analysis etc.) provides an idea of the model and of a general view of the tectonomagmatic processes going on there.

Data of seismological, gravimetric and electromagnetic study are presented. Main peculiarities of deep-seated structure of the earth's crust and upper mantle to the depth of ~90 km have been revealed. Margins of the lithosphere blocks on ground and water area of the Avacha bay have been established. A complex geologic-geophysical model beneath Avachinsky volcano has been developed. It involves crustal magmatic chamber at depth 15 to 25 km, intrusion overlying it, peripheric chamber at depth ~0 to 2 km, and zone saturated with liquid fluids in Avachinsky graben. Major geodynamic processes, which have been operating in the earth's crust at present, are considered. An important role is given to the crustal permeable zone containing fluids. Recommendations are made for the deep well-drilling in the area of Avachinsky volcano with the aim of searching for geothermal deposits.

Рассматриваются особенности гравитационного поля в районе вулкана М. Семячик. Положительная аномалия Δg, совпадающая с современным конусом, объясняется влиянием периферического магматического очага. Определены размеры и форма этого очага. Его особенностями являются высокое положение верхней кромки и переменная по глубине избыточная плотность 0,5-0,3 г/см3. Отрицательные аномалии объясняются воронками взрыва, параметры которых близки к параметрам кальдеры, образовавшейся при катастрофическом взрыве Кракатау в 1883 г.

Results are presented from gravity, seismic and electromagnetic studies. Main features of the deep structure of the area have been identified. A multidisciplinary geologic-geophysical model has been developed for the crust beneath Avacha Volcano. The model involves a crustal magma chamber at a depth of about 15-25 km, an intrusion that overlies it, and a peripheral chamber under the volcanic cone at 0-2 km depth, as well as a fluid-saturated zone in the Avacha Graben. We discuss possible geodynamic processes that are going on in the crust at present. Importance is attached to the fluid-containing crustal permeable zone. Recommendations are provided for drilling a deep well in the Avacha Graben area to search for a geothermal field.