Journal of Volcanology and Seismology最新文献

Archeological, archeoseismological, historical, and macroseismic studies were conducted in the Samanid Mausoleum and in the Magoki-Attori mosque identifying the presence of various seismic deformations in the walls of these ancient buildings. These include dips, bulging, collapses and rotations of structural elements around the vertical axis, as well as cracks of various origins. These seismic damage and collapses were caused by past large earthquakes: 1390 and those in the 19th century; there are other signs of damage whose ages and location are still to be determined. The aniceint sources of seismic oscillations lay south of Bukhara, the Gazli earthquakes occurred north of the town. The data we obtained indicate probable strong earthquakes occurring in the Bukhara region once per a few hundred years. Local seismic intensity caused by near earthquakes can reach values I_l = 8‒9 intensity units. There is an effect that enhances the earthquake impact; this concerns settling processes developing in unconsolidated soils where Bukhara stands, as well as a high groundwater level. The source of these seismic events is the Gazli–Karatag fragment of the South Tien-Shan seismic zone, as e.g., faults of adyr folds growing near the town.

This paper is concerned with the study of microseismic motion in the upper crustal layer as inferred from in situ data recorded by laser interferometric instruments and a broadband seismometer during the passage of typhoons in 2018 through 2020. Our analysis has revealed a relationship between the periods of microseisms as recorded by the laser strainmeter and sea swell as recorded by a laser meter of hydrosphere pressure variations.

This paper considers the conditions of formation for the epithermal Au–Ag mineralization at the Televeem volcano dome rise (VDR) lying in the Central Chukchi sector of the Okhotsk–Chukchi Volcanogenic Belt (OChVB). New data are provided for the composition, distribution, and concentrations of rare elements, including REE, in epithermal ores, and the PТ parameters of ore-forming fluids. Appreciable enrichment of REE samples, the dominance of light lanthanoids over heavy ones, very low Eu/Sm ratios (( ll 1)), slightly inclined near-chondrite distribution patterns with well-pronounced europium minima, are all typical features for the VDR epithermal ore-forming system. The values of Ce/Ce* vary between low negative and moderately positive (between 0.81 and 1.38), while the Eu/Eu* ratio varies between 0.28 and 0.7, which provides evidence of oxidating conditions prevalent during the mineralization. The results of thermal and cryometric studies of fluid inclusions in quartz have revealed that the ore-forming fluid contained chlorides of Na, Mg, and K, the epithermal mineralization was deposited by homogeneous hydrothermal fluids with salt concentrations (0.3–6.2 wt %-equi. NaCl), the fluid had density 0.60–0.87 g/cm³, the temperatures were 203 to 343°C, the pressure of water vapor varied between 40 and 140 bars. The geochemical data and the PТ parameters of the ore-forming fluids showed that the mineralization was of the low sulfidation epithermal class. These data indicate andesitic magmas and meteoric waters as the most likely sources of the fluids. The information provided in this paper is of practical importance for regional metallogenetic prediction, for the search for and evaluation of epithermal Au‒Ag deposits.

The eastern branch of Icelandic rifts includes the Northern and the Eastern Rift Zones whose morphologies are rather different; this is determined by different period of their formation, as well as by the structural and kinematic position relative to the Reykjanes and Kolbeinsey spreading ridges, the rift zones of the western branch, and the center of the Icelandic plume. The Northern Rift Zone includes both mature central volcanoes containing long fissure swarms, and embryonic edifices within the latter ones. The Eastern Rift Zone contains large conic and shield edifices of central volcanoes and comparatively young fissure swarms. We sought to reveal the present-day tectonic structure and geodynamic processes by morphometric analysis that included examination of variation for five parameters of fault scarps along the striking of the rift zones. The present-day propagation of the Northern Rift Zone is northward; the propagation does not occur throughout the entire length of volcanic systems, but focuses on individual fault groups. The present-day structural rearrangement of the Northern Rift Zone implies a gradual simplification of its tectonics, resulting in the formation of an en-echelon structure that includes several short segments of volcanic systems. At the same time, tectono-magmatic activity gradually concentrates in the western part of the rift zone. The Eastern Rift Zone divides into two separate branches having similar parameters of tectono-magmatic activity, with no signs of an ongoing structural rearrangement being observed at present, even though the western branch is recedes southwards. In addition, a relationship has been identified between the parameters of the fault scarps and the rheologic properties of the crust: in the conditions of higher magmatism and a shallower magma chamber, it is observed shorter and high-density fault groups of small amplitude, and frequent seismic activity.

This paper reports the results of laboratory experiments in the interaction of meteoric water and distilled water with the Shiveluch ash discharged during the eruption of April 11–13, 2023. The water extracts obtained using a variety of methods made it possible to simulate naturally occurring situations in which ash falls in a water environment and is washed by atmospheric precipitation. It has been found that the salt complex of Shiveluch Volcano contains a well-soluble component, viz, sodium chloride, magnesium salts, and a poorly soluble component consisting of calcium sulfate. The water extracts of fresh ashes contain high (relative to the concentration in the rocks of Shiveluch edifice) concentrations of volatiles (boron and selenium), as well as calcium, copper, and rare earth elements. The level of rock relationships was observed in some alkaline (Li, Na, K, Sr), high-charge (Y, Pb), and transitional (Zn, Ni, Co, Mn) elements. The transfer ratios for the other elements are very low, including rock-forming ones (Fe, Al, Si, Ti). Water extracts having ash–water ratios of ∼1 : 10 contain higher concentrations of fluoride ions reaching 3 MAC (maximum allowable content) and of sulfate ions reaching 2 MAC relative to the maximum allowable concentrations in objects of household-drinking and cultural water use. Ash that is washed by atmospheric precipitation loses its toxic potential during a few months. Stagnant water bodies favor accumulation of soluble components of volcanic origin, because water extracts show exceedance of safe parameter values in several heavy metals, the water–ash system is a dynamic one. The highest exceedance of maximum allowable content have been found for aluminum, manganese, copper, and cadmium. Also, volcanic ash can be a source of prolonged supply to drinking water of mixtures that are subject to regulations because they affect the quality of potable water.

This paper presents quantitative estimate of the influence of near-bottom pressure due to wind waves and sea swell on the upper crustal layer based on data recorded by a laser meter of hydrosphere pressure variations and by two laser strainmeters. The processing and analysis of these data revealed that the coefficient expressing the transformation of near-bottom pressure in the shelf area of the Japan Sea due to marine wave processes into elastic oscillations of the crust is dependent on the periods of progressive sea waves.

This paper proposes a novel method for describing earthquake waveforms based on the transformation of seismic waveforms to mesofluctuations (MSF). These cumulative MSF representations ignore high-frequency (fine-scale) oscillations but effectively preserve the waveform envelope and enable accurate detection of the onset, amplitude, and decay duration of P- and S-waves. These key features serve as the foundation for the architecture of the proposed neural network RSNet (Russian Seismic Net) designed for automatic detection of body wave onsets (P- and S-phases) using computed mesofluctuation metrics. In contrast to existing neural network models that rely on raw three-component seismograms, the proposed method operates on reduced and intermediate-scale (mesoscale) metric representations derived from mesofluctuation analysis – specifically, signal range and its first derivative. This approach enhances interpretability and robustness under noise, while reducing the dimensionality of the input data. The model was trained and validated using the STEAD database, which includes over 1 million labeled seismograms. The mean absolute error (MAE) of wave onset detection was 0.04 s for P-waves and 0.13 s for S-waves. When benchmarked against phase picks generated by the PhaseNet neural network, the MAE for S-waves decreased to 0.10 s. These results are comparable to the accuracy of the state-of-the-art neural-network models, while RSNet offers distinct advantages in interpretability and resilience to external noise factors.

This paper is concerned with the present state of the thermal fields in the near-summit part of the active Ebeko Volcano on Paramushir Island (Kuril Islands). We show the area of occurrence, the discharge, and the chemical composition of the main types of water manifestations (pots, lake, springs). All thermal occurrences on the volcano resulted from interaction between volcanic gases on the one hand and the surface and underground waters circulating at small depths on the other; the thermal occurrences have low pH (<3), Cl–SO₄ (SO₄–Cl) composition in a wide range of temperatures (between 10 and 98°C) and salinity (between 1 and 100 g/L). Based on continuous multiyear observations of the evolution of chemical composition in thermal waters we estimated the response of volcanic events to the state of the hydrothermal system. We showed that changes in the chemical composition of Lake Goryachee are related to changes in the intensity (going as far complete decay) of hydrothermal activity in the Middle Crater. The phreatomagmatic eruption beginning in 2016 might have provoked the resumption of deep fluid flow into the lake, resulting in increased concentrations of Cl^– in the water. The pots in the Northeastern Field are the most sensitive to events occurring on the volcano. All periods of increased activity are recorded in the varying concentrations of ({text{SO}}_{4}^{{2 - }}) and Cl^– and in the relationships between the two after the increase in activity began. However, even the largest pots periodically become steam–gas jets, which impedes regular geochemical monitoring.

Integrated geological and structural geophysical studies have shown that the South Kambalny Central Thermal Field was formed in the crater of a cone belonging to a Pliocene–Pleistocene volcano at the Kambalny Range. A geothermal reservoir has been identified beneath the thermal field; this is a rock volume rich in aqueous and steam-gas fluids. The center of the thermal field contains a zone of less dense rocks which controls the flow of ascending alkaline metal-bearing brine and is interpreted as the vent of a crater. We studied the structure of a sequence of hydrothermal clays and argillized, zeolitized, and carbonized bedrock basaltic andesites that form the base of the clay sequence. We provide a detailed characterization of newly formed mineral compounds in deposits of three types: siliceous sediments occurring along the periphery of the thermal field; carbonate concretions at the base of the hydrothermal clay sequence; and altered basaltic andesites. We have provided a substantiation: the hydrothermal mineralization, including ore mineralization, is an indicator of the influence of the deep-seated alkaline metal-bearing fluid on the zone of vapor-rich hydrothermal fluids. It is hypothesized that the sources of ore compounds, as well as of nitrogen and phosphorus, may be due to basite intrusions identified in the southern group of thermal fields in the Kambalny volcanic range.

A fresh eruption of the Yuzhno-Sakhalinsky mud volcano on Sakhalin Island was detected when the volcano was visited in late May 2011. The eruption was surveyed and described, data on ground movements were used to develop a model for the eruption source. Much later, when Landsat 5 and Landsat 7 satellite images were analyzed, it was found that the eruption occurred in the time interval between 19 and 211 hours after the Tohoku earthquake, Northeast Japan. The epicentral distance (on the order of 10³ km) and the magnitude (M = 9.0–9.1) of that earthquake satisfy the well-known relationships which are used to find the triggering threshold, i.e., the possibility for an earthquake to serve as a trigger to start the eruption of a mud volcano. It was therefore concluded that the eruption of the Yuzhno-Sakhalinsky mud volcano can have been a response to the Tohoku earthquake. If that was the case, then this would be the first reliably recorded and carefully studied response of a mud volcano to an earthquake at that great distance.