V004-0001
Anatomy of the Bezymianny Volcano (Kamchatka, Russia) just before an Explosive Eruption on 20.12.2017 based on Seismic Tomography, Petrology and Satellite Imaging

Monday, 7 December 2020
Poster
Ivan Koulakov, Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia, Thomas Walter, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany, Pavel Plechov, Fersman Mineralogical Museum, Moscow, Russia, René Mania, Deutsches GeoForschungsZentrum GFZ, Potsdam, Germany, Sergey Z. Smirnov, V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia and Sergey Senyukov, Kamchatkan Branch of Geophysical Survey RAS, Petropavlovsk-Kamchatsky, Russia
Abstract:
Explosive volcanoes are associated with a massive ejection of a huge amount of gases and ash that pose a threat for air traffic and population in surrounding areas. However, subterranean precursors of such eruptions are commonly challenging to identify. On December 20, 2017, a strong explosion occurred at Bezymianny in Kamchatka, one of the most active volcanoes of the World, that ejected an ash plume to the altitude of ~15 km. We used the data recorded by temporary and permanent seismic stations to build 3D distributions of seismic wave velocities in the upper crust corresponding to a few days prior to the eruption. The derived model highlights both a shallow magma chamber and a large high-pressure gas reservoir, which is presumed to be the main driver of this explosion. We further test this hypothesis with petrological analysis that is supporting the interaction of the magma and gas sources. The process of fracturing of shallow layers beneath the volcano edifice in the last days prior to the eruption was investigated based on the seismicity evolution, satellite radar imagery and degassing measurements captured by time-lapse cameras.

Figure caption: Petrological analyses and interpretation of the seismic tomography model. (a and b) BSE images of two types of juvenile material. (a) JM1 porous basaltic andesite with glassy groundmass. (b) JM2 porous andesite with tridymite and glass in groundmass. Pl - plagioclase, Px - pyroxene, Gl - glass, Tr - tridymite, V - vapor bubbles. (c) Schematic image of the plumbing system prior to the eruption. Background is the distributions of the Vp/Vs ratio along the vertical section crossing Bezymianny in the NW-SE direction. Dotted line depicts the area of possible storage and migration of gases. Areas of possible origin of samples JM1 and JM2 are indicated with arrows.

This study is supported by the RSF grant #20-17-00075.

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