IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

3A2_1B-O10

Room B1

Date/Time: July 23 11:45-12:00

The New Tolbachik Fissure Eruption in Kamchatka, 27.XI 2012-2013. Earthquakes
Preceding the Event and First Estimates of its Duration
Sergey A. Fedotov2 , Alexey L. Sobisevich1 , Lidia B. Slavina1
1

Institute of the Physics of the Earth, Russian Academy of Sciences, Russia, 2 Instiute of Volcanology
and Seismology, Far East Branch, Russian Academy of Sciences, Russia
E-mail: alex@ifz.ru

Magmatic feeding system and mechanisms of activity of the Kliychevskaya Group of Volcanoes (KGV) areconsidered. The KGV is one of the most significant volcanic center in subduction zones. It is located in thenorthern part of the Kuril-Kamchatka volcanic belt and consists of: the Kliychevskoi basaltic stratovolcano (thelargest erupting volcano in Eurasia), the Bezymianny andesite volcano, the basaltic Hawaiian-type Plosky Tolbachik
volcano (PT) with summit caldera, the Tolbachinskaya zone of cinder cones and fissure eruptions (TZ) and theUshkovsky volcano.
In 1975-1976 the Great Tolbachik Fissure Eruption (GTFE) in TZ produced 2.2 km3 of basalts.
Development of the New Tolbachik Fissure Eruption (NTFE) started 27.XI 2012 is analysed, including: the locationof the feeding fissure and the two eruptive centers on it in TZ; effusive nature of eruption with lava flows of liquidalumina basalts produced during the first two months covering an area of more than 27 km2.
Remarkable features of the process of local seismic activation preceding the NTFE are considered. Increase inthe number of earthquakes under PT (at a depth of about 4 km near the peripheral magmatic chamber of PT) has
started in mid-2012 and continued up to the beginning of NTFE. It has culminated during the last two days before
NTFE in the form of a large swarm of small earthquakes that propagated towards to the surface. The swarm was
the forerunner of the impending eruption and highlighted the position and depth of magma origin of the NTFE .
It is demonstrated, that during the first months, until January 20, 2013, NTFE was the large fissure lava eruption,
slowly decreasing over time. Quantities of produced material and duration of such eruptions are subject fortheoretical estimations. The first rough estimates have been given for the NTFE on December 15, 2012 andon January 22, 2013 respectively.
The initial forecast has assumed continuation of the NTFE while the amount of volcanic products will not exceed
the amount of alumina basalts (500 million tons) potentially accumulated in the peripheral magmatic chambers of
the PT volcano. Thus in this case, an exponential decay of the eruptive activity could last up to 110 days.
According to preliminary estimates of volumes of erupted lava in the NTFE, available by mid-January 2013,
the number of produced basalts significantly exceeded the volume of excess magma, potentially located in theperipheral magma chamber of the PT volcano. For the next forecast the redundant magma volume accumulated
up to the NTFE in magmatic systems throughout the KGV (2,100 million tons) has been considered as a possible
upper limit of the volume of eruptive products. In this case, the volume of lava produced by the NTFE may exceed1 km3 and reach the amount of lava erupted in the Southern breakthrough of the GFTE in 1976. Thus, the NTFE
may continue for up to 300 days.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

72