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.

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.

Рассмотрены методика и результаты магнитотеллурического зондирования в модификациях АМТЗ и МТЗ. Аудиомагнитотеллурическое зондирование (АМТЗ) было проведено впервые в районе современного извержения Толбачинского вулкана. Результаты анализа магнитотеллурических параметров свидетельствуют, что геоэлектрическую среду, в связи с региональным разломом, можно аппроксимировать в виде двумерно-неоднородной модели. В качестве основных для интерпретации приняты продольная и поперечная кривые зондирований. Совместный анализ этих кривых и псевдоразрезов фаз импеданса свидетельствуют о геоэлектрической неоднородности среды в районе прорыва магматических расплавов им. С.И. Набоко. По данным бимодальной инверсии кривых АМТЗ получен геоэлектрический разрез, содержащий проводящую неоднородность, связываемую с разломом, по которому флюиды поступают к дневной поверхности. Наряду с АМТЗ для изучения глубинной электропроводности использованы МТЗ в расширенном диапазоне, по которым выделяется коровая проводящая аномалия на глубинах 15–35 км. По данным АМТЗ, МТЗ и другой геолого-геофизической информации составлена концептуальная модель района, характеризующая возможную природу аномальных зон. Даны приближенные оценки пористости пород в разломной зоне, по которой магматические расплавы поступали в вышележащие толщи в районе прорыва им. С.И. Набоко.

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.

Long-term investigations in the Ushkovsky Volcano caldera were completed in June 1998 using deep drilling of the crater glacier filling the Gorshkov summit cone. A 212-m ice core containing 354 bands of volcanic ash was obtained. The possibility of using an analysis of these data in paleovolcanic reconstructions of the northern volcano group is discussed.