Journal of Volcanology and Seismology最新文献

This paper provides a synoptic review of the cycle of studies performed by a team affiliated with the IPE RAS in order to look for new approaches to problems of earthquake physics. The fundamental Omori, Gutenberg–Richter, and Bath laws invariably served as the basis and guiding light during our research for many years. The concept of a triad of tectonic earthquakes as a natural trinity of foreshocks, main shocks and aftershocks is used in the paper to arrange thematic material. We provide a classification for main shocks as part of six types of triad identified experimentally. We list the parameters involved in the three laws for the different triad types. An axiomatic theory is given to describe aftershock evolution. We define new concepts, viz, source deactivation, Omori epoch, and source bifurcation; as well, we introduce the concept of proper time for nonstationary lithosphere processes. Convergence of foreshocks and divergence of aftershocks are mentioned. The general conclusion runs as follows: the Omori, Gutenberg–Richter, and Bath laws provide a reliable basis for experimental and theoretical study of earthquakes. These laws possess deep content, which made itself felt in the possibility of enriching the original formulations of the first discoverers with interesting and important additional statements

We provide data on the major and trace element composition of deep waters in the productive reservoirs beneath the Mutnovsky geothermal field confined to the eponymous active volcano in southern Kamchatka. The goal of the present study was to reveal the key role of deep-seated heat carrier in the formation of gold–silver mineralization taking the Mutnovsky geothermal system as an example. Several significant gold–silver ore deposits lie near the system. It has been found that deep waters are mostly alkaline (pH 8.85–9.74) or near-neutral (pH around 6), as well as chloride–sulfate or sulfate–chloride, potassium–sodic or sodium-potassic waters. The salinity varies in the range 260–4465 mg/L. It has been found that salinity is appreciably higher in alkaline waters than in near-neutral. Among the elements reliably detected, the highest concentrations occur for Br, As, Se, Sr, Ba, Li, Ag, and Zn. The suspended particles found in water samples contain compounds such as poorly soluble iodargyrite AgI, naumannite Ag₂Se, and electrum (Au, Ag). At present these minerals are formed within the areas of deep-seated vapor-dominated hydrothermal fluids belonging to the Mutnovsky field, forming regions of present-day mineral generation. Arsenic, antimony, selenium, and tellurium occur in alkaline environments in mobile water-soluble forms, and chloride ions favor the mobilization of noble metals, e.g., gold and silver, which tend to make polysulfide and chloride complexes. The mobilization of ore elements increases in alkaline environments owing to the formation of hydroxy complexes, so that for this case alkaline waters have the highest ore potential with regard to noble-metal mineralization.

The earthquake size is quantified by seismic centers all over the world in several magnitude scales, which requires to be unified into a preferred scale to infer flawless comparison of earthquake size. The problem has been addressed by numerous researchers and converted earthquake magnitudes mostly into moment magnitude from different magnitude scales as relation among them are overdue. In this study, Simple Linear Regression (SLR), Orthogonal Regression (OR), Gaussian Process Regression (GPR), and Support Vector Regression (SVR) have been employed to find out the best method to correlate different earthquake magnitude scales. The Andaman–Nicobar–Subduction Zone, a part of the Sumatra–Andaman–Subduction–Zone which is capable of producing earthquakes of great magnitudes, has been selected for this study. For this study, earthquake data has been extracted from the International Seismological Centre (ISC) earthquake catalog. The study indicates that moment magnitude can be predicted more accurately using multiple scales than single scale. It has also been found that, the GPR model predicts higher earthquake magnitude values better than other methods. Hence, for conversion of earthquake magnitude into standard scale, use of multiple scales and the GPR method can be beneficial.

The present paper reports a study and refinement of quality parameters for data acquired using the seismological network in the area of the Lena R. delta. The main estimated metrics were chosen to be sensitivity and azimuthal gap between neighboring stations. For assessing scenarios to be used in the deployment of network stations we chose the area where we estimated mean sensitivity as having the highest priority, and mean azimuthal gap. We planned the station locations so as to optimize the network sensitivity with an eye to ensuring that the mean azimuthal gap should be below 180°. This assessment of the current arrangement resulted in the decision to dismantle the SML09 station to transfer the equipment to a more promising location. In addition, we propose a scenario for the deployment of additional stations increasing the mean sensitivity by 0.49 in the area of interest. This would result in the number of recorded earthquakes increasing by a factor of 2.08, as follows from the Gutenberg–Richter relation.

The isotopic K–Ar ages of the volcanoes in the interfluve of the Kozyrevka and Malaya Romanovka rivers in the Sredinny Range of Kamchatka have been determined for the first time. We have identified six phases of activity: the end of the Miocene (5.8–5.5 Ma), the Early Pliocene (4.9–4.5 Ma), the Middle Eopleistocene (1.5–1.4 Ma), the Late Eopleistocene (1.1–1.0 Ma), and the Middle Pleistocene (two phases: 0.6 and 0.4–0.3 Ma). No later volcanism has been recorded in the region. It was found that the start of Quaternary volcanic activity was preceded by a repose period lasting approximately 3 Ma. It was found for the first time that the major fault striking northeast at the northern base of Romanovka Volcano could not have originated before 0.4–0.3 Ma B.P. An analysis of isotopic K–Ar dates suggests that the phases of Quaternary volcanic activity that occurred ∼1.5 and ∼0.3 Ma B.P. were regional in character. Regional activity was less pronounced for the phases ∼1.0 and ∼0.6 Ma B.P. The rocks discharged in the interfluve during the last six million years ranged between basalts and dacites. It was found that the extensive covers and major lava edifices are composed of intermediate and acid rocks, while basalts are confined to small monogenic centers. Overall, the volcanics studied here have chemical compositions that are similar to those of the Late Miocene–Quaternary rocks in the southern Sredinnyi Range. The results of our study alter significantly the previous age estimates for the volcanoes in the area of study at the Sredinnyi range. We suggest that no significant glaciation has occurred in the interfluve of the Kozyrevka and Malaya Romanovka at least during Quaternary time.

Mutnovsky Volcano is characterized by predominantly magmatic activity for the last 4 thousand years in the northern sector where the Mutnovsky geothermal field lies. Magmatic activity is identified using the Frac-Digger method based on seismic data as reported by the KB FRC UGS RAS. The most significant sequence of shallow dikes striking northeast has been manifested at the surface by blowing two-phase geothermal wells. Dike emplacement in March 2024 was synchronized with a hydrothermal explosion producing a crater of volume reaching 0.36 million m³ at the place of well 022 (Crater 022+). Unaltered fragments due to the explosion indicate a lithoclastic character in the gas-enriched head of the dike. The bottom of the explosion crater is a hydrothermally altered (opal, zeolite) 160 × 75 m² in area. The mechanism of the hydrothermal explosion is treated as resulting from hydraulic fracturing by means of a shallow dike, with subsequent increase in pressure in the shallow geothermal reservoir near the well with a closed wellhead control-valve.

Tephra of two generations has been identified in sediments of the numerous lakes lying from the coast of the Sea of Okhotsk in the south as far as the Indigirka River basin in the north. Tephra of different ages differs in area of occurrence, and in petromagnetic, geochemical, mineralogical, and thermomagnetic characteristics, thus enabling reliable identification in sections. The accumulation of lower tephra was due to an eruption that formed the caldera of Lake Kurilskoe in Kamchatka about 7600 B.P. It has been found in all lakes where sedimentation was occurring at that time. The character of tephra occurrence was controlled by the distance to the source, by morphologic and hydrodynamic parameters of the lakes, as well as by post-sedimentation processes. The tephra has a rhyolitic composition with silica concentrations of 75.6–75.9%; it is low-magnetic. The magnetic particles are mostly pseudo-single-domain ones. The tephra is dominated by titanomagnetites with mean concentrations of titanium within ∼3.6–6.5 wt %. The upper tephra only occurs in the northern Okhotsk region. It shows high magnetic properties and is dominated by low-titanium titanomagnetites (Ti = 2.6–3.2 wt %). The magnetic particles are pseudo-single-domain to multidomain (closer to multidomain). The magnetic susceptibility of the tephra layers, which is an order higher than that of the host sediments, is its leading distinctive feature. The tephra has a rhyodacitic composition with silica concentrations of 70.2–70.5%. Its age is about 3000 years. The tephra interbeds in lake sediments are important chronological and correlative markers of the Holocene.

This study is concerned with the mineralogical and petrochemical composition of the gabbro sampled on the Esmeralda submarine volcano in the southern Mariana island arc. The dredging was carried out during the 4th and 5th cruises of the research vessel Vulkanolog. It has been found that the gabbro, which belongs to the tholeiitic series, are strongly fractionated rocks, unlike the gabbroids dredged in basins of the southern Mariana island arc system. It is shown that this gabbro typically contains higher concentrations of iron. This higher concentration of iron is confirmed by high concentrations of iron in pyroxenes and plagioclase, which enables us to classify the bulk of dredged gabbro as belonging to the association of arc ferruginous tholeiites. Low concentrations of high charge and heavy rare-earth elements relative to MORB, as well as their interelement relationships, imply the formation of primary melts from a source in a depleted mantle. The enrichment of gabbro in large-ion lithophile elements provides evidence that the magma genesis not only involved high-temperature residual melt, but was also significantly affected by low-temperature fluid components.

This paper presents the results of a study of sublimates (mineral deposits from volcanic gases) that have been collected in silica tubes placed at high-temperature vents in the Eastern Fumarolic Field of Avachinsky Volcano, Kamchatka in 2013–2023. The ICP-MS and ICP-AES methods were used to obtain the concentration distributions for 62 elements throughout the tube lengths, i.e., along the temperature gradient. A total of 35 sublimate phases corresponding to naturally occurring minerals have been identified, in addition to 7 sublimate phases for which there are no naturally occurring analogues, or they are still unknown. The overall mineral sequence with decreasing temperature is as follows: Na and K halogenides; Na, K, and Ca sulphates; sulfides; As–S amorphous glass, and Tl, Pb, and Bi halogenides. The most abundant phases are As–S glass, SiO₂ (cristobalite), NaCl, KCl, Na₂SO₄‒K₂SO₄; rare phases: KCdCl₃, K₂Pb(SO₄)₂, Tl(I, Cl, Br), Pb₂Tl(Cl, I, Br)₅, PbTl₃(Cl, I, Br)₅, Pb(Cl, I, Br)₂, Tl₃BiI₆, ReS₂, the sulfides of Pb–Zn–Cd–In and AgI.