We present the results of time-dependent local earthquake tomography for the Kluchevskoy group of volcanoes in Kamchatka, Russia. We consider the time period from 1999 to 2009, which covers several stages of activity of Kluchevskoy and Bezymianny volcanoes. The results are supported by synthetic tests that recover a common 3D model based on data corresponding to different time windows. Throughout the period, we observe a robust feature below 25 km depth with anomalously high Vp/Vs values (up to 2.2). We interpret this feature as a channel bringing deep mantle materials with high fluid and melt content to the bottom of the crust. This mantle channel directly or indirectly determines the activity of all volcanoes of the Kluchevskoy group. In the crust, we model complex structure that varies over time. During the pre-eruptive period, we detected two levels of potential magma storage: one in the middle crust at 10–12 km depth and one close to the surface just below Kluchevskoy volcano. In 2005, a year of powerful eruptions of Kluchevskoy and Besymiyanny volcanoes, we observe a general increase in Vp/Vs throughout the crust. In the relaxation period following the eruption, the Vp/Vs values are generally low, and no strong anomalous zones in the crust are observed. We propose that very rapid variations in Vp/Vs are most likely due to abrupt changes in the stress and deformation states, which cause fracturing and the active transport of fluids. These fluids drive more fracturing in a positive feedback system that ultimately leads to eruption. We envision the magma reservoirs beneath the Kluchevskoy group as sponge-structured volumes that may quickly change the content of the molten phases as fluids pulse rapidly through the system.

This paper presents results from a study of lava flows that were discharged by Bezymyannyi Volcano at different times, from old (about 3500 years ago) to recent ones (1985–1989). We provide detailed descriptions of the composition, structure, and petrophysical properties for the main types of constituent rocks, which are andesites and basaltic andesites. It was found that porosity is the leading factor that controls rock properties, while the effects of structural and mineralogical features are less prominent. We demonstrate the variation in the properties of rocks that compose the lava flows in relation to their ages: the older a rock is, the higher its density and strength and the lower its porosity is.

This is the first petrophysical study of extrusive rocks (dacites to andesites) discharged by Bezymianny Volcano. We provide a comparative description of properties for extrusive rocks in accordance with identified age groups. We show the dynamics in the variation of extrusive rock properties in relation to their ages, with the result that the older a rock the higher are its density, strength, and elastic parameters. Rocks petrophysical features are compared between extrusive domes and lava flows. We argue for petrophysical properties to be applicable for deriving more accurate results for the genesis of rocks having similar petrophysical properties, in particular, rocks of extrusive and effusive origin.

This paper presents the results of visual observations, particle-size analysis, seismological observations, and acoustic measurements carried out during a small-magnitude eruption of Bezymyannyi in June 1986. A mlodel is proposed for the mechanism of the eruption. A specific character of the eruption is explained by a deeper localization of a gas-rich aagia portion in the conduit,