Shiveluch volcano: seismicity, deep structure and forecasting eruptions (kamchatka)
ABSTRACT The deep structure, Wadati-Benioff zone (focal zone) geometry and the magma feeding system of Shiveluch volcano are investigated based on 1962–1994 detailed seismic surveillance.A focal zone beneath Shiveluch is dipping at an angle of 70° at depths of 100–200 km. Based on the revealed interrelations between seismicity at depths of 105–120 km and an extrusive phase of its eruptions in 1980 through 1994, it is inferred that primary magmas, periodically feeding the crustal chamber, are melted at depths of at least 100 km. An upsurge of extrusive-explosive activity at the volcano is preceded and accompanied by the increasing number and energy of both volcanic earthquakes beneath the dome and tectonic or volcano-tectonic earthquakes in the zones of NW-striking crustal faults near the volcano.The eruption of April 1993 has been the most powerful since 1964. It was successfully predicted based on interactive use of all seismic data. At the same time the influence of seismicity at depths of 105–120 km under the volcano on the style (and consequently on prediction) of its activity is decisive.
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ABSTRACT: There have been three episodes of lava dome growth at Shiveluch volcano, Kamchatka since the Plinian explosive eruption in 1964. The episodes in 1980–1981, 1993–1995 and 2001–2004 have discharged at least 0.27 km3 of silicic andesite magma. A time-averaged mean extrusion rate of 0.2 m3/s is thus estimated for the last 40 years. Here the 2001–2004 activity is described and compared with the earlier episodes. The recent activity involved three pulses in extrusion rate and a transition to ongoing lava extrusion. Estimated magma temperatures are in the range 830 to 900 °C, with 850 °C as the best estimate, using the plagioclase−amphibole phenocryst assemblage and Fe−Ti oxides. Melt inclusions in amphibole and plagioclase have maximum water contents of 5.1 wt.%, implying a minimum pressure of ∼ 155 MPa for water-saturated conditions. The magma chamber depth is estimated to be about 5–6 km or more, a result consistent with geophysical data. The thicknesses of opx–mt–amph reaction rims on olivine xenocrysts are used to estimate the residence time of olivine crystals in the shallow chamber in the range 2 months to 4 years, suggesting replenishment of deeper magma into the shallow chamber contemporaneous with eruption. The absence of decompression-driven breakdown rims around amphiboles indicates ascent times of less than 7 days. Volcanological observations of the start of the 2001–2004 episode suggest approximately 16 days for the ascent time and a conduit equivalent to a cylinder of diameter approximately 53–71 m. Application of a conduit flow model indicates that the magma chamber was replenished during the 2001–2004 eruption, consistent with the results of olivine reaction rims, and that the chamber has an estimated volume of order 7 km3.Journal of Volcanology and Geothermal Research 07/2006; · 2.19 Impact Factor
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ABSTRACT: A data base for the composition and emission rates of more than 100 thermal manifestations including boiling geothermal systems and 23 volcanoes along the 1900km long Kamchatka–Kuril (KK) arc is presented. These results were used to estimate mean fluxes of volatiles from the KK arc. The fluxes from the KK arc are compared with the fluxes from the best studied Central American (CA) arc and with the compiled literature data on global fluxes. The error ranges and the OUT/IN (in)balance calculations are also discussed. The estimated fluxes of volatiles from volcanic fumaroles and the observed, normalized to the Cl content, fluxes from hydrothermal systems are very close, with the higher hydrothermal flux from Kuril Islands due to a larger number of the acidic Cl–SO4 springs on the Islands and their outflow rates. The total volcanic SO2 flux from the whole KK arc is estimated to be higher than 3000t/d. The measured S and C fluxes from hydrothermal systems are much lower than the volcanic output due to the loss of these components in the upper crust (mineral precipitation). The Cl/3He ratio is inferred to be a stable indicator of the arc setting for hydrothermal and volcanic fluids with a mean value of (2±4)×109. Comparison of the obtained volcano–hydrothermal fluxes with fluxes calculated from the erupted solid volcanic products at Kamchatka and Kurils during Holocene time reveals that the total estimated volatile output from the KK arc is compatible with the total magmatic output if the intruded to erupted ratio is close to 7, i.e. almost the same as assumed for the Central American arc. Calculated fluxes as well as the ratios for OUT/IN fluxes (volcanic+hydrothermal output/slab+mantle input) for CO2, S, H2O, Cl, N2, 4He and 3He from the KK arc normalized to the arc length are in general close to the global estimates. The fractions of CO2 and S in the total volatile output at KK arc derived directly from the mantle wedge are 18% and 16% (mole basis), respectively. Fractions of mantle derived H2O, N2 and Cl are much lower, less that 5% of their output.Geochimica et Cosmochimica Acta 01/2009; 73(4):1067-1094. · 3.88 Impact Factor
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ABSTRACT: We give an overview of the 2005–2011 eruptions of Shiveluch Volcano together with the seismicity and deformations of the lava dome during dome growth. It is shown that the generation of the intracrater intrusive dome proceeded at a variable rate. The maximum discharge of erupted lava reached 0.6 million cubic meters per day. Increased explosive activity preceded periods of intensive growth of the lava dome. We determined the volumes and depths of the magma chambers that supplied magma for large eruptions of the volcano on November 12, 1964, February 28, 2005, and October 27, 2010. We calculated the effective viscosity of the 2007 and 2011 lava flows.Journal of Volcanology and Seismology 7(2). · 0.20 Impact Factor