This paper describes a large landslide that occurred on Zheltovsky Volcano in summer 2012. The article describes main features of the volcanic edifice and considers parameters of the landslide. The landslide was likely caused by the altered rocks in the summit area as well as water infiltration during snow melting. No significant seismic or meteorological events had been registered immediately prior to the landslide. This example shows that large landslides at the volcanic edifices may occur without catastrophic precursors, which makes the hazard assessment more difficult. The paper is based exclusively on the remote sensing data most of which are available online from open sources.

New isotope-geochemical data for Jurassic-Cretaceous volcanic rocks from Streltsovkaya caldera allowed us to reveal the existence of several sources of the melts from which caldera igneous rocks were formed. Mantle melts (basalts and trachybasalts) were melted from mantle garnet lherzolites characterized by εNd(T) = -0.9 — 3.4, ISr(T) = 0.7056-0.707, Zr/Nb = 14-30, Nb/U = 4-8, Th/Ta = 5-15. The Streltsovskaya caldera magmatism began 160 million years ago. Apparently, it was genetically related to the onset of stretching in China and Mongolia. The mantle region from which were melted the late Jurassic-early Cretaceous melts in the Streltsov caldera, Bolshoj Khingan belt, Eastern China, southern Mongolia by isotope-geochemical characteristics can be combined into a single domain that differs from other mantle domains in China.

We use SESL’09 technique for a unified estimation of seismicity level in a given space-time regions. The application of the distribution function of radiated seismic energy permits the formalization of qualitative description of seismicity. We present the results from statistical estimations of seismicity level before the 2000- 2012 Bezymianny Volcano eruptions. The state of seismicity was describes by the monogram, constructed according the SESL’09 technique. By processing the Klyuchevskoy volcano group seismic catalog, we estimated variations of seismicity and detected background level. Statistically significant variations of the seismicity level preceded the eruptions were detected and discussed.

По данным микросейсмического зондирования построена глубинная модель среды под районом Узон-Гейзерной вулкано-тектонической депрессии и прилежащего к ней вулканического массива Кихпиныч (Камчатка) до глубины 30 км. Для этого была осуществлена регистрация естественного фонового микросейсмического поля переносными широкополосными сейсмометрами Guralp CMG-6TD в точках специально спланированной наблюдательной сети: в 60-ти точках вдоль трех профилей общей длиной около 28 км. Выявленные структурные неоднородности проинтерпретированы с учетом известных ранее результатов геологических, геолого-морфологических и петрологических исследований. Идентифицирована и пространственно локализована область малоглубинного закристаллизовавшегося магматического очага под депрессией. Выявлены области предположительной концентрации базальтовых расплавов, с которыми может быть связана наблюдающаяся в последние ~ 15 лет локальная геодинамическая активизация исследуемого района: периферический магматический очаг вулканического массива Кихпиныч на глубине 5-12 км, более глубокая (15-20 км) магматическая камера. Получено согласие геометрии обнаруженных глубинных структур с локальной микросейсмичностью и моделью современного магматического внедрения в верхние горизонты коры, разработанной по данным спутниковой интерферометрии.

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.