S. A. Fedotov

The magmatic system of the Klyuchevskaya group of volcanoes inferred from data on its eruptions, earthquakes, deformation, and deep structure

The study of magmatic plumbing systems of volcanoes (roots of volcanoes) is one of the main tasks facing volcanology. One major object of this research is the Klyuchevskaya group of volcanoes (KGV), in Kamchatka, which is the greatest such group that has been found at any island arc and subduction zone. We summarize the comprehensive research that has been conducted there since 1931. Several conspicuous results derived since the 1960s have been reported, emerging from the study of magma sources, eruptions, earthquakes, deformation, and the deep structure for the KGV. Our discussion of these subjects incorporates the data of physical volcanology relating to the mechanism of volcanic activity and data from petrology as to magma generation. The following five parts can be distinguished in the KGV plumbing system and the associated geophysical model: the source of energy and material at the top of the Pacific Benioff zone at a depth of about 160 km, the region of magma ascent in the asthenosphere, the region of magma storage in the crust-mantle layer at depths of 40–25 km, magma chambers and channelways in the crust, and the bases of volcanic edifices. We discuss and explain the properties of and the relationships between these parts and the mechanisms of volcanic activity and of the KGV plumbing system as they exist today. Methods for calculating magma chambers and conduits, the amount of magma in the system, and its other properties are available.

The peripheral magma chamber of Ploskii Tolbachik, a Kamchatka basaltic volcano: Activity, location and depth, dimensions, and their changes based on magma discharge observations

The Klyuchevskoi group of volcanoes (KGV) in Kamchatka is the most powerful existing island arc and subduction zone volcanic center. The Holocene volcanic activity in the southern part of the KGV is concentrated in a large basaltic volcano, Ploskii Tolbachik (PT), altitude 3085 m and in its Tolbachik zone of cinder cones (TZ), length 70 km, which are similar to Hawaiian-type volcanoes and their rifts. A variety of different basalt types are erupted at a rate of 18 × 106 t/yr.This paper provides information on the PT peripheral magma chamber obtained by several independent methods. We used data on the evolution, eruptions, magma discharge, deformation, and earthquakes in the PT and TZ, as well as calculations that give the size of the PT flow-through magma chamber. The use of seismological and geodetic data places the chamber under the PT summit caldera, gives its transverse size as below 6 km, and the top of the chamber at a depth of 2 km. Our calculations give 4.9–5.8 km for the transverse chamber dimension, 3.2–3.9 km for its vertical dimension, 40–70 km3 for chamber volume, and about 4 km for the depth of chamber center.The information we provide makes the properties of this source of PT and TZ alumina-rich basalts clear, as well as those of the entire KGV complex plumbing system.

On the eruptions, deformation, and seismicity of Klyuchevskoy Volcano, Kamchatka in 1986–2005 and the mechanisms of its activity

The eruptions, seismicity, and deformations, the properties of the magma feeding, and the mechanism of the activity of Klyuchevskoy, a giant basaltic volcano in Kamchatka, are considered. Twenty-eight author’s papers on the above subjects, published from 1985 to 2006, are reviewed. The activity of Klyuchevskoy the adventive and summit eruptions of Klyuchevskoy from 1986 to 2005 is described. The seismicity of Klyuchevskoy from 1986 to 2005 and its relation to eruptions are considered. It was inferred from geodetic measurements that the center of the magmatic pressure beneath the volcano moved in the depth range from 3 to 25 km during the period from 1979 to 2005. Based on previously developed models and observations from 1986 to 2005, the main properties of the Klyuchevskoy magma feeding system and the magma ascent in five major parts of the system are described and characterized: near the top of the plunging Pacific plate (with a depth of approximately 160 km), in the asthenosphere (160 to 40 km), in the region of the intermediate magma chamber where the magmas coming from below are accumulated (40 to 20 km), in the crust (20 to 5 km), and in the upper part of the system (from a depth of 5 km under the volcanic edifice to the crater at an altitude of 4.75 km). A comparison between the outputs from the summit and adventive eruptions on Klyuchevskoy as functions of time for the period from 1978 to 2005 shows that the probability of adventive eruptions should increase in the future.

A Long-term earthquake forecast for the Kuril-Kamchatka Island arc for the period 2006–2011 and a successful forecast of the MS = 8.2 middle kuril earthquake of November 15, 2006

Results are reported from continuous long-term earthquake prediction work for the Kuril-Kamchatka island arc using the patterns of seismic gaps and the seismic cycle. A five-year forecast (April 2006 to April 2011) for all portions of the Kuril-Kamchatka seismogenic zone is presented. According to this, the most likely locations of future M ≥ 7.7 earthquakes include the Petropavlovsk-Kamchatskii area where the probability of an M ≥ 7.7 earthquake causing ground motions of intensity VII to IX in the town of Petropavlovsk-Kamchatskii is 48% for 2006–2011, and the area of Onekotan I. and the Middle Kuril Islands where the probability of an M ≥ 7.7 earthquake was estimated as 26.7%. The forecast was fulfilled on November 15, 2006, when an Ms= 8.2, Mw = 8.3 earthquake occurred in the Middle Kuril Islands area. An updated long-term forecast is presented for the Kuril-Kamchatka arc for the period from November 2006 to October 2011. These forecasts provide good reasons to enhance seismic safety by strengthening buildings and structures in Kamchatka.

A long-term earthquake forecast for the Kuril-Kamchatka arc for the period from September 2011 to August 2016. The likely location, time, and evolution of the next great earthquake with M ≥ 7.7 in Kamchatka

We consider the results from the ongoing 2010–2011 work on long-term earthquake prediction for the Kuril-Kamchatka arc based on the pattern of seismic gaps and the seismic cycle. We develop a forecast for the next 5 years, from September 2011 to August 2016, for all segments of the Kuril-Kamchatka arc earthquake-generating zone. For 20 segments we predict the appropriate phases of the seismic cycle, the normalized rate of small earthquakes (A10), the magnitudes of moderate earthquakes to be expected with probability 0.8, 0.5, and 0.15, and the maximum possible magnitudes and probability of occurrence for great (M ≥ 7.7) earthquakes. This study serves as another confirmation that it is entirely necessary to continue the work in seismic retrofitting in the area of Petropavlovsk-Kamchatskii.Independent additional estimates of the likely location, time, and evolution of the next M ≥ 7.7 earthquake in Kamchatka were obtained by considering same-type scenarios in the evolution of foreshock sequences, main shocks, and aftershocks for the last three great earthquakes in Kamchatka: November 22, 1969; December 15, 1971, and December 5, 1997.The giant Tohoku earthquake of March 11, 2011 (Mw = 9, M = 8.9) filled the seismic gap as identified in our 2005 forecast for northeastern Japan.

A long-term earthquake forecast for the Kuril-Kamchatka arc for the period from September 2010 to August 2015 and the reliability of previous forecasts, as well as their applications

We describe results from the ongoing 2008–2010 work on long-term earthquake prediction for the Kuril-Kamchatka arc based on the patterns of seismic gaps and the seismic cycle. We provide a forecast for the next 5 years, September 2010 to August 2015, specified for all segments of the earthquake-generating Kuril-Kamchatka arc zone. For 20 segments we predict the phases of the seismic cycle, the normalized rate of small earthquakes (A10), the magnitudes of moderate earthquakes to be expected with probabilities of 0.8, 0.5, and 0.15, the maximum possible magnitudes, and the probabilities of great (M ≥ 7.7) earthquakes. It is shown that the forecast given for the previous 5 years, from September 2005 to September 2010, was found to be accurate. We report the measures that were taken for seismic safety and retrofitting based on these forecasts.

On the possibility of using heat stored in the magma chamber of the Avachinsky volcano and the surrounding rock for heat and power supply

The results of geological and geophysical studies, including recent ones, which make it possible to verify the existence of a liquid magma chamber below the Avachinsky volcano on Kamchatka, and to estimate the chamber depth and approximate dimensions, are analyzed. The heat stored in the host rock heated by the volcanic magma chamber from the time of chamber origination to the present is estimated, taking variable chamber dimensions during the process of evolution into account. The geological-geophysical prerequisites for using the thermal energy of the heated rock which surrounds the magma chamber to supply heat and power to Petropavlovsk-Kamchatskii are analyzed. The creation of an underground geothermal circulation system (fracture heat exchanger) using deep boreholes is proposed.

A geomechanical interpretation of the local seismicity related to eruptions and renewed activity on Tolbachik, Koryakskii, and Avacha Volcanoes, Kamchatka, in 2008–2012

The local seismicity during the 2012–2013 eruption of Tolbachik Volcano and the 2008–2009 steam–gas eruption of Koryakskii Volcano is here considered as resulting from injections of magma that produced dikes, sills, and renewed activity at preexisting faults. We identified plane-oriented earthquake clusters in order to reveal the above zones using earthquake catalogs made at the Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS). Subsequent space–time analysis of these observations lends itself to the following interpretation. The November 27, 2012 Tolbachik lava eruption was preceded by an injection of magma resulting in a series of dikes trending west-northwestward in the range of absolute depths between–4 and +3 km in a zone situated southeast of the Ploskii Tolbachik Volcano edifice. The dikes penetrated into a nearly horizontal permeable zone at an absolute depth of approximately zero, producing sills and emplacing a magma-conducting dike along the top of the zone of cinder cones (the dip angle is 50° toward the azimuth 300°) 5.5 km from the epicenter of the initial magma injection. The summit steam–gas eruption of Koryakskii Volcano in 2008–2009 was preceded by magma filling a crustal chamber (the top of the chamber is at–3 km absolute depth; the chamber is 2.5 km across) close to the southwestern base of Koryakskii. Further, magma injection in a nearly north–south zone (7.5 by 2.5 km), the absolute depth between–2 and–5 km) in the north sector of Koryakskii Volcano was occurring concurrently with the summit steam–gas eruption. The injection of magma into the cone of Avacha Volcano (2010) produced sills (at altitudes between +1600 and +1900 m) and dikes (mostly striking northwest).

Detailed Seismological Investigations in Kamchatka during the 1961-2011 Period: Main Results

On November 1, 2011 it was 50 years since the beginning of detailed seismological investigations in Kamchatka. The Kamchatka regional network of seis mic stations was set up in 1961 by the Pacific Seismic Expedition (abbr. PSE, see a list of abbreviations at the end of the main text), IPE, USSR Acad. Sci. as a joint venture with the Multidisciplinary Geological and Geophysical Observatory SB USSR Acad. Sci. and directed by S.A. Fedotov, Head of the PSE.

Aftershocks and the rupture zone of the MS = 8.2, November 15, 2006 Middle Kuril Is. Earthquake and a long-term earthquake forecast for the Kuril-Kamchatka arc for the period from April 2008 to March 2013

Results are reported from the ongoing 2007–2008 work using the method of long-term earthquake prediction for the Kuril-Kamchatka arc based on the patterns of seismic gaps and the seismic cycle. This method was successful in predicting the MS = 8.2 Simushir I. (Middle Kuril Is.) earthquake occurring in the Simushir I. area on November 15, 2006. An MS = 8.1 earthquake occurred in the same area on January 13, 2007. We consider the evolution of the seismic process and determine the common rupture region of the two earthquakes. The sequence of M ≥ 6.0 aftershocks and forecasts for these are given. We provide a long-term forecast for the earthquake-generating zone of the Kuril-Kamchatka arc for the next five years, April 2008 to March 2013. Explanations are given for the method of calculation and prediction. The probable locations of future M ≥ 7.7 earthquakes are specified. For all segments of the earthquake-generating zone we predict the expected phases of the seismic cycle, the rate of low-magnitude seismicity (A10), the magnitudes of moderate-sized earthquakes to be expected, with probabilities of 0.8, 0.5, and 0.15, their maximum possible magnitudes, and the probabilities of occurrence of great (M ≥ 7.7) earthquakes. The results of these forecasts are used to enhance seismic safety.