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We analyze the results of geophysical studies of the crust and upper mantle which were carried out in 2000–2013 in the Kamchatka isthmus area. The obtained data reveal obduction (thrusting of suboceanic lithosphere upon the margin of the continental one) in the study area, indicating potentially high seismic hazard in the entire frontal zone of obduction. A comprehensive geological–geophysical model is developed along the profile that passes between Ossora and Tilichiki settlements, along the obduction front. In 2013, strong seismic activation was recorded in the northeastern part of the region; the Il’pyr earthquake was the first in the series. The comparison between modeling results and the real seismic lineament shows that tectonic stresses accumulate on the faults between lithospheric blocks and then release in the form of seismic events, as was recorded in the obduction zone between Ossora and Tilichiki settlements in March–May 2013.

The results of the magnetotelluric (MT) soundings before and after an earthquake are analyzed. The interpretation is based on the longitudinal and transverse MT curves (along and across the strike of the main tectonic elements, respectively). The MT curves are distorted by the ρ- and coast effect. The distortions due to the coast effect are estimated by the testing three-dimensional (3D) model. It is established that the coast effect distortion at the periods up to 1000 s is small and can be disregarded. The divergence of the longitudinal and transverse MT curves, which points to the presence of the deep faults, is thoroughly studied. The inversion of the MTsounding curves is carried out by the REBOCC program of the numerical two-dimensional modeling. This program implements the procedures of elimination of the ρ-effect and the joint inversion of the longitudinal and transverse MT sounding curves. The obtained geoelectrical cross sections provide an insight into the structure of electrical conductivity of the lithosphere before and after the earthquake. The more intense variations in the electric conductivity are observed in the zone of the deep faults. These variations are related to the changes in the porosity and saturation of the rocks by the highly mineralized fluids.

The structure of the Earth’s crust and upper mantle has been estimated by using geologic-geophysical cross-sections developed along two orthogonal geophysical profiles in the area of the Tolmachevsky active magmatic center. Comprehensive geophysical data have revealed the existence of an intrusive massif of predominantly intermediate-medium-felsic composition whose formation is accounted for by the presence of powerful heat flows and local melting sites. A swarm of small earthquakes reported in 1987-1988 was triggered by the advance of magma in the zone of the assumed eruptive fissure. Meteoric waters interact with the high-temperature media through the infiltration zone, which results in intense hydrothermal activity including the formation of steam-hydrothermal occurrences. The area of the proposed intrusive body is a promising zone for a high-temperature geothermal reservoir.

The article discusses the results of the interpretation of magnetotelluric sounding (MTS) data generated in the vicinity of the Mutnov steam hydrothermal deposit during the period from 2004 to 2006. Approaches to an interpretation of magnetotelluric (MT) data in a situation characterized by significant 3D distortions and the coastal effect phenomenon are discussed. The resulting 3D geoelectric model is presented. Based on analysis of the created geoelectric model, the principal geoelectric horizons are characterized, which includes the parameters of the integral conductivity and the morphology of the geoelectric boundaries. Zones of the highest values of the electrical conductivity of the watered tuffaceous sediment horizon have been identified, as well as zones of the maximum lateral electrical conductivity contrasts that are interpreted as discharge zones of hydrotherms. The results of the drilling carried out based on MTS data are presented.