No 2 (2019)

Hydrogeoseismological Research in Kamchatka: 1977–2017
Kopylova G.N., Boldina S.V.

Abstract

This paper is concerned with the main stages in the setting-up and technical development of a system specializing in physical and chemical parameters of groundwater at a network of wells and springs in the Petropavlovsk Geodynamic Test Area, Kamchatka. The focus is on a description of hydrogeochemical and hydrogeodynamic precursors to Kamchatka earthquakes (Мw = 6.6‒7.8) that occur a few weeks to a few months before a seismic event, manifesting themselves in anomalous changes in chemical composition and groundwater level. The precursors are discussed in application to their use at specialized councils on earthquake prediction. It is shown that the system of automated observation of groundwater parameters at wells as developed at the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences (KB GS RAS) is capable of identifying hydrogeodynamic precursors of water-level in near real time and of providing, in some particular cases, quantitative estimates of pre-seismic and coseismic deformation of water-saturated rocks. This can be useful in geophysical monitoring and intermediate-term prediction of strong earthquakes for the Kamchatka region.

Вулканология и сейсмология. 2019;(2):3-20
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Using the Paratunsky geothermal field to provide heating for Kamchatka
Kiryukhin A.V., Zhuravlev N.B.

Abstract

The Paratunsky geothermal field has been in operation since 1964, mostly in a self-flowing mode, with a discharge rate of approximately 250 kg/s of thermal water at temperatures of 70–90°С (47 Mw, with the waste water having a temperature of 35°С). The water drawn from the field is used for local heating, spa heating, and for greeneries in the villages of Paratunsky and Termal’nyi (3000 residents). The potential market of thermal energy in Kamchatka includes Petropavlovsk-Kamchatskii (180000 residents), Elizovo (39 000), and Vilyuchinsk (22 000). The heat consumption in the centralized heating systems for Petropavlovsk-Kamchatskii is 1 623 000 GCal per annum (216 Mw). A thermohydrodynamic model developed previously is used to show that the Paratunsky geothermal reservoir can be operated in a sustainable mode using submersible pumps at an extraction rate of as much as 1375 kg/s, causing a moderate decrease in pressure (by no more than 8 bars) and temperature (by no more than 4°С) in the reservoir. Additional geothermal sources of heat energy may include the Verkhne-Paratunsky and Mutnovsky geothermal fields.

Вулканология и сейсмология. 2019;(2):21-33
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Volcanism and geochemistry of soil and vegetation cover of Kamchatka. Communication 1. Geochemical features of volcanic surface ashes
Zakharikhina L.V., Litvinenko Y.S.

Abstract

Common geochemical features of volcanic near-surface ashes of Kamchatka (ashes located under the surface organogenic soil horizons) are their depletion by most chemical elements in comparison with average indicators for volcanic rocks of corresponding composition and relative enrichment of a limited range of elements, mainly typomorphic for main rocks (P, Mg V, Cr, Cu, Zn, Zr, Sb). Against the background of small variations in the contents of chemical elements in the ashes of different areas of the peninsula, the range of their priority elements is determined by their petrochemical composition. The active activity of the Northern group of volcanoes of Kamchatka causes a relatively high content of mobile forms of elements in the near-surface ashes of the Northern province in comparison with the ashes of the southern part of the peninsula.

Вулканология и сейсмология. 2019;(2):34-44
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Evolution of gas hydrates accumulation in zones of submarine mud volcanoes
Sobisevich A.L., Suetnova E.I., Zhostkov R.A.

Abstract

The article examines the processes of evolution of gas hydrate accumulations, related to submarine mud volcanoes. A mathematical model and the results of numerical modeling of the accumulation of gas hydrates in the seabed in the deep structures of underwater mud volcanoes are presented.

Numerical analysis of the influence held feeder layer depth and pressure therein to the evolution of gas hydrate saturation confined to deep water mud volcanoes were performed. Modeling quantitatively showed that hydrate saturation in areas of underwater mud volcanoes is not constant and its evolution depends on the geophysical properties of the bottom medium (temperature gradient, porosity, permeability, physical properties of sediments) and the depth of the supply reservoir and pressure in it, and the rate of hydrate accumulation in tens and hundreds times the rate of hydrate accumulation in the sedimentary basins of passive continental margin.

Вулканология и сейсмология. 2019;(2):45-51
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Earthquake july 17, 2017, Mw = 7.8 near the Komandorsky islands and strong seismic manifestations in the western segment of Aleut island arc
Lutikov A.I., Rogozhin E.A., Donzova G.Y., Zhukovez V.N.

Abstract

The tectonic position, seismological characteristics and features of the aftershock process of the source of the strongest Near-Aleutian earthquake on July 17, 2017 on the Commander Islands with Мw = 7.8 are considered. The analysis showed that the seismic source according to the distribution of aftershock epicenters in the form of a linearly elongated narrow zone with a length of about 400 km almost completely occupied the northern slope of the Commander island elevation and was located in the Bering fault zone. It covered the whole of this seismic-generating zone up to the transverse structure to the west of the Near Islands (Attu is.). In accordance with the focal mechanisms solution and the nature of the displacements in the foci of the main shock, the strongest foreshocks and aftershocks, the shift in the source was an almost pure right-sided shift. The aftershock process of the July 17 earthquake developed quite enough inertly for an earthquake of such strength. In addition, it has two features in comparison with the aftershock processes of most of the Kuril-Kamchatka earthquakes: 1) low release of the cumulative scalar seismic moment (M0cum aft), which according to various estimates was from 0.75% to 1.0% of the seismic moment of the main shock (M0me); 2) a very slow increase in the deficit in the release of the seismic moment (M0). At the same time, the duration of the quasi-stationary phase of M0cum release in aftershocks, estimated at about ½ year and covering a significant part of the duration of the entire aftershock process of this earthquake, seems unusually long. These features of the aftershock process of the Middle Aleutian earthquake on July 17, 2017 distinguish it from the aftershock processes characteristic of most strong Kuril-Kamchatka earthquakes. In general, its source can be considered as a transform between the two Benioff zones – Aleutian and Kuril-Kamchatka, and not subduction, that is characterise the last two.

Вулканология и сейсмология. 2019;(2):52-66
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Global statistics of aftershocks following large earthquakes: independence of times and magnitudes
Baranov S.V., Shebalin P.N.

Abstract

This paper considers the global statistics of times of largest aftershocks relative to the times of the corresponding main shocks. A large data set was used to show that the time-dependent distribution of largest aftershocks obeys a power law distribution. This is analogous to the Omori law for the sequence of all after- shocks. It is also shown that the times of the second, etc., largest aftershocks obey the same distribution. Thereby, we have confirmed the hypothesis that the times and magnitudes in an aftershock sequence are independent and make a good case for the Reasenberg-Jones representation of the aftershock process as a superposition of the Omori-Utsu law and the Gutenberg–Richter relation. Events that are smaller than the largest in an aftershock sequence show no delay relative to the largest event; this rejects the idea of the after- shock process as a direct failure cascade involving gradual transitions from larger to lesser scales, which imposes certain restrictions on the widely popular stochastic models of aftershock generation as branching processes. The above result is important in practice for prediction of aftershock activity and for assessing the hazard of large aftershocks.

Вулканология и сейсмология. 2019;(2):67-76
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