Journal of Volcanology and Seismology最新文献

This paper reviews the results of fundamental importance achieved by the Institute of Volcanology and Seismology (IV&S), Far East Branch (FEB), Russian Academy of Sciences (RAS) for the period 1962‒2021. We consider the most important achievements classified under the following headings: Volcanological research includes petrologic and geochemical features of ejecta by volcanoes in the Kuril–Kamchatka region; the age of volcanoes and the phases of volcanogenic catastrophism in Kamchatka; hydrothermal systems and geothermal reserves of Kamchatka; hydrothermal metasomatism and volcanogenic mineral generation and mineralization; Geophysical research includes the seismology of volcanoes; deformation at active volcanoes; tectonic earthquakes and tsunamis; the internal structure of volcanic systems.

This paper discusses the data of instrumental observations conducted at the Mikhnevo Observatory, at INTERMAGNET observatories, and at the Geophysical Monitoring Center of the Institute of Geosphere Dynamics (IGD), Russian Academy of Sciences (RAS) during the explosive eruption of Hunga Tonga-Hunga Ha’apai Volcano of January 15, 2022. It is shown that the explosion of the volcano produced a series of wave disturbances in the atmosphere, as well as electrical and magnetic variations at large epicentral distances. The atmospheric disturbances were recorded as Lamb waves emitted by a source at the center of the explosion, as well as by a virtual source situated at the antipode. The latter source was formed by convergence and summing of signals propagating on the terrestrial sphere. In addition to primary waves, the recorded phenomena also include secondary and tertiary waves due to multiple passage of the explosion-produced signal around the terrestrial sphere. We evaluated the source energy based on the characteristic frequency in the spectrum of the signal, resulting in the value ~10¹⁸ J, which corresponds to ~200 MT of TNT, when converted to an explosive source. It is shown that a volcanic explosion is accompanied by electrical and magnetic variations both at the time of the explosion and at the time when the recording site receives atmospheric wave disturbances.

This paper is a review of our work, an experimental study and simulation of seismic fields in volcanic structures using vibrators as sources of elastic waves. We review the results of experimental studies of mud volcanoes carried out by the Institute of Computational Mathematics and Mathematical Geophysics (ICM&MG) of the Siberian Branch (SB), Russian Academy of Sciences (RAS); by the Institute of Physics of the Earth (IPE), RAS; and by the Kuban State University in the Taman mud-volcanic province using vibrators. We have carried out mathematical simulation in heterogeneous geophysical media to refine the information on the structure of the object under investigation, as well as on the distinguishing features of the seismic field. We have developed a mathematical approach to deal with the simulation of vibroseismic probing of mud volcanoes with arbitrary geometries incorporating knowledge of deep-seated faults, overlapping layers, and so on. Numerical techniques were used to solve sets of equations in elasticity theory and to develop parallel algorithms, program packages, as well as carrying out numerical experiments in high-performance computational systems. We present results from calculations of the seismic field for the source zone of the Shugo mud volcano. This paper describes 3D and 2D geophysical models developed for this study and the results of simulation for the seismic field of the Karabetova Gora mud volcano and for the Elbrus magmatic volcano. It is shown that the approach developed here using active vibroseismic techniques can be successfully used in practice to refine the seismic field, the deep structure of geophysical models, and to study the effects exerted by the geometry of a magma chamber and by the presence of erupting channels on data acquired by an observation system on the ground surface. These studies prove that vibroseismic sources with high accuracies of periodic excitation can be used to study volcanic structures and to conduct active monitoring of volcanic activity.

This paper reports on new data concerning the chemical and isotopic composition of volcanic gases, the emission of volcanic SO₂ and of soil CO₂ at the active Ebeko Volcano. The volcano erupted in 2009, 2010, 2011, from October 2016 to November 2021. The composition of volcanic gases for 2003–2016, 2021 was obtained by straightforward sampling of the fumaroles. The high-temperature gas (420–529°С) has a composition that is typical of Kuril magmatic gases with an atomic ratio C/S <1 and the concentration of HCl 5–7 mmol/mol; the isotopic composition of the condensates: δD ~ –24, δ¹⁸O = 2.6–4.9. We have identified geochemical precursors of the eruption: increasing concentrations of CO_2, Н₂, SO₂, H₂S, and HCl; decreasing C/S ratio down to values below 1, which is characteristic for magmatic gases at the Kurils; increasing temperature; heavier isotopes of δD and δ¹⁸O in condensates of volcanic vapor; increasing gas flux. The accumulation chamber technique was used to measure a high soil flux of CO₂ in two thermal fields (reaching 10 442 g/m²/day), which exceeds the visible fumarolic output (~50 t/day as against ~40 t/day). The flux of SO₂ from the active crater was measured using a DOAS scanning HC spectrometer in 2020 and in 2021, and was 99 ± 28 and 9 ± 2.7 t/day in gas plumes, and 747 ± 220 and 450 ± 130 t/day in ash plumes, respectively. The decreasing emission of SO₂ in August 2021 is here related to degassing of the magma before the termination of the eruption.

The present paper gives a scale of earthquake energy class K^F that is to standardize the relevant data based on the existing scales: M_S, M_W, mb, K_S, among many others. The conceptual novelty of the scale we propose consists in shifting the emphasis from seismometric issues that are traditional in such cases, which are concerned with the recording of seismic waves, as well as with issues arising in discussions of their generation and propagation, toward an effective use of basic energy properties of the seismic process (the Gutenberg–Richter law). In the most general case, this approach can significantly simplify the development of regression relations between different earthquake size scales, but the most promising problem consists in developing a single generalized scale. A particular solution of the problem is presented as the development of such a scale for earthquakes of Kamchatka. The K^F scale rests on the energy class (K_{{S1.2}}^{{F68}}) proposed by S.A. Fedotov (K_S at the Kamchatka Branch (KB) of the National Seismological Centre, Geophysical Survey, Russian Academy of Sciences (NSC GS RAS) and on the generally accepted mb magnitude (ISC).

This study is concerned with deviations of the rate of vertical crustal movements based on data of broadband seismic stations from the theoretical values of earth tides. The deviations were compared with information on meteorological conditions at station sites. It is shown that the deviations reach half the daily variations in tidal amplitude and rate of change during rains. Our hypothesis is that the phenomenon can be explained by the Rehbinder effect.

The paper addresses megacrysts of “bubbly” kaersutite found among mantle xenoliths in the Al Ghab plateau basalts, northwestern Syria. The xenoliths as all xenoliths worldwide are represented by two series: green spinel peridotites (mainly lherzolites) and cross-cutting veins rocks of “black series” (mainly kaersutite hornblendites and kaersutite clinopyroxenites). It is believed that the parental melts/fluids of the “black series” were formed under decompressional fluid-assisted melting of the plume’s spinel peridotites at the late stages of development of the plume-related magmatic systems. “Bubbly” kaersutite megacrysts are fragments of pegmatoid varieties of the “black series” rocks. They represent monocrystals up to 10 cm long, which contain numerous relatively large cavities partially filled with volcanic dust. It is shown that the “bubbly” structure of these megacrysts is explained by their crystallization during retrograde boiling of parental melt/fluid in the mantle plume head at a pressure of 9–10 kbar. The oval cavities initially represented bubbles of high-density carbon dioxide entrapped by growing crystals. These bubbles were likely degassed during eruption and CO₂ has been partially preserved only in some microscopic bubbles. It was also shown that the parental melt contained small suspended drops of fluid-saturated high-Fe liquid, which were likely derived through liquid immiscibility before retrograde boiling of the melt/fluid.

This paper presents data on the activity of Shiveluch Volcano (56.6° N, 161.4° E) during the new 2001‒2021 eruptive cycle. We analyze the growth of new extrusive features, provide information on the large explosive eruptions and their impact, discuss a plausible scenario for catastrophic eruptions in the near future. Continuous 4-year video observations of Shiveluch emissions resulted in assessment of its thermal power and pyroclastic material volume based on the emissions of steam–gas jets.

We used data acquired during field surveys conducted over the years to study the macro component and micro component composition of water in Lake Zelenoe in the Troitsky Crater of active Maly Semyachik Volcano. We showed that the lake contains ultra-acid (pH < 1) water of sulfate–chloride composition with mineral concentrations between 8 and 42 g/L, depending on the state of the volcano. The anion composition of this lake is formed by inflow and subsequent dissolution of acid volcanic gases in an aquifer horizon situated immediately below the lake. The cation composition of the water is controlled by practically congruent dissolution of host rocks. A long period of repose was followed in 2008 by a new phase in the hydrothermal activity of the volcano lasting until today. Upon the background of a constantly increasing volume we observed increasing concentrations of main macro components (SO₄, Cl, Al, Fe), and of mineral content in general.

The early post-eruptive activity is described on the Third Cone, one of the New Tolbachik volcanoes, formed during the eruption at the Northern Breakthrough during the Great Tolbachik Fissure Eruption, which occurred in Kamchatka in 1975–1976. Changes in temperature, exhalation mineral generation, and rock alteration in the fumarole areas of the northern and southern craters of the Third Cone are characterized.