Abstract—This paper is concerned with ground deformation and seismicity prior to the Tolbachik Fissure Eruption, which began in Kamchatka on November 27, 2012. Seismic and GPS data were analyzed to reveal synchronous precursory anomalies in crustal deformation and seismicity that lasted approximately 4 months (August to November 2012). The seismic anomaly was a statistically significant increase of seismicity with low energy (mostly KS = 4–6) beneath the Ploskii Tolbachik Volcano edifice at depths of less than 5 km. The rates of seismicity and seismic energy release were exceeded by factors of approximately 40 compared with the
2000–2011 mean values during the 2 to 3 weeks immediately before the eruption. The strain anomalies were observed as movements in the middle of the Klyuchevskoy volcanic group: a radial (relative to the eruption) compression and an extension in the tangential direction. The strain had reached ~ 10^–7 by the beginning of the eruption. The durations of the seismic and strain anomalies were comparable in value (~ 4 months before the eruption), thus providing evidence of a common origin. We can classify them as belonging to the same time scale of precursors (the intermediate�term in the accepted terminology).

Sedimentary and volcanic-sedimentary rocks from natural exposures on the Phu-Qui and Katuik volcanic islands (Vietnam Shelf) have been analyzed for their elemental composition. Mineralogically and petrochemically, sandstone rocks of Phu-Qui Island are petrogenic compounds and refer to subarkose. Judging by the prevalence of quartz and feldspar, by the dominance of sialic association in the heavy mineral fraction as well as by the pattern of major, minor and rare-earth element distribution, the main sources of clasts were intrusive and metamorphic rocks of the mature continental crust, and sedimentation settings correspond to passive continental margins. The Middle Pleistocene volcanic-sedimentary rocks of the Phu-Qui – Katuik group of islands are composed of pyroclastic material of mafic composition close to the basalts from trachybasalt-trachytic and alkaline basaltic series of Vietnam, which possess intraplate characteristics and relate to the existing here extension settings. The sedimentation occurred in subaerial environment near the centers of volcanic eruptions.

The article provides an algorithm for recovery of parameters of ash emissions (total volume and its height distribution) during explosive eruptions. The solution for the corresponding inverse task uses a multiple regression approach with minimal a prior information on the eruption dynamics. As an example, we consider a strong explosive event at Bezymianny Volcano, Kamchatka, on 24.12.2006. The estimations showed that the mass distribution for ash emission with heights was partially controlled by the emission of ash material inside the clouds from pyroclastic flows. This peculiarity was revealed as a bimodal distribution of the emission mass with maximums at the mid tropospheric and low stratospheric heights.

The article describes the alternative mechanisms of earthquakes and volcanic eruptions in which the leading role is played by the deep compact fluid areas. Redistribution of fluid pressure between these areas due to the migration of fluids along fractures and faults can provoke seismic and volcanic activity in the region, as well as determine the different sorts of their interdependence.

The monograph is devoted to the spatio-temporal activation of Holocene volcanism within the Miocene-Quaternary volcanic zone of the Sredinny Range of Kamchatka. The pattern of volcanic activation, grouping elements and periodic pulses of endogenous activity, as well as their chronological relationship with episodes of endogenous activity increasing of the North Pacific. The characteristics of individual volcanic centers and the largest eruptions are provided. Age determinations of eruptions are based on detailed tephrochronological research and extensive radiocarbon dating.
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