Journal of Volcanology and Seismology最新文献

This paper considers the propagation of ash during the paroxysmal eruption of Sheveluch Volcano which occurred April 10–13, 2023, and its impact on the water resources of the affected area. We characterize ash thicknesses at various population centers and describe the grain-size composition of the ash. We show that the propagation of ash plumes is primarily driven by the eruption dynamics, but atmospheric circulation actually controls the spatial distribution of deposit thickness. The water-soluble salts contained in the ash and the dynamics of their washing out under natural conditions have been determined. The water-soluble part of fresh ash is dominated by calcium and magnesium sulfates, sodium chloride, with minor amounts of chlorides and fluorides of aluminum, potassium, and ammonium. The first substances to be washed out from ashes are well-soluble chlorides, to be followed by sulfates. As time goes on, the total concentration of soluble salts is decreasing, and their qualitative composition changes: hydrogen carbonates of calcium, magnesium, and sodium begin to dominate. Several months after the eruption, the impact of the ashfall on water resources of the settlements, including open springs at the ground surface, was leveled out.

The Tonga-Kermadec subduction zone lies between the Pacific and Australian plates. The location shows the highest rate of subduction for the Pacific plate and a dominant tension. Two great earthquakes occurred in the region in 2006 and 2009 whose magnitudes were M_w = 8.0 and 8.1. There are about 170 islands around the Tonga subduction zone; these islands are volcanic centers that have been regularly in eruption during the last several decades. The present study presents the results from the determination of time-dependent variations in the slope of the recurrence curve (the b-value) at the Tonga subduction zone during 2005–2022, and depth-dependent variations in b. The time-dependent variations in b reflect the general tendency of great earthquakes occurring upon the background of lower b-values in the surface layer only, at depths of 0–100 km. The comparison between the depth-dependent variations in b and the tectonic model for the Toga subduction zone implies the hypothesis that lower b-values may reflect greater stresses in the upper part of the plunging plate due to its bending. Higher b-values seem to be connected to tensional mechanisms. A region of higher b-values at depths of 90–100 km has been identified for the Tonga subduction zone, as well as for other subduction zones, which can be related to the presence of a magmatic front at these depths, which is related to active volcanism.

This paper is concerned with the distribution of heat flow in the Baikal Rift Zone, the Shanxi-Liaohe Rift, the Jordan Rift, and in the Orly (Storoya) Trough in the northern Svalbard plate, as well as in the rift zone of Iceland. One notes an asymmetry in heat flow about the rift axial line compared with adjacent areas upon the background of its higher value. The origin of this asymmetry is due, not only to differences in the permeability of the faults in the sides of the rift structure, but also to planet-wide factors, in particular, the Coriolis force. The north–south rift structures considered here are situated in the northern hemisphere; their eastern flanksshow increased heat flow compared with the western flanks, and this is in agreement with the Coriolis force vector in the Earth’s northern hemisphere. The geothermal asymmetry in oceanic crustal divergent zones as noted previously is also seen in pull-apart structures of continental rift zones.

This work is concerned with classification and study of the composition and properties of hydrothermal zeolites from the Yagodninskoe deposit, (Kamchatka) which were formed in volcanic rocks. The study involved X-ray phase analysis and X-ray fluorescence, optical and scanning electron microscopy. We determined specific syrface AREA the pore size distribution, as well as cation exchange capacity in zeolites. The study resulted in the identification of four main rock types at the deposit: the original unaltered perlites, zeolites rock, zeolitized tuffs, as well as poorly zeolitized tuff breccias. The Content of zeolite group minerals reaches 70%. The minerals mostly include clinoptilolite and, to a lesser degree, mordenite, stilbite, and heulandite. The zeolites are of the alkaline type, with the cation exchange capacity equal to 205.9 mg-equi/100 g. It has been found that these zeolites were mostly formed from perlites and tuff breccias. It is pointed out that the Yagodninskoe zeolites are high quality minerals, and make a promising object of further exploration.

We have carried out a correlation analysis to study relationships between the trace element (TE) composition of mud-volcanic and carbon dioxide fluids in the Greater Caucasus on the one hand and the chemical composition of upper, middle, and lower crust, as well as various kinds of biota on the other hand. It has turned out to be possible to relate the roots of the associated fluid flows with definite stages of the Earth’s crust, as well as to point out, in several cases, the kind of the dominant original organic matter. The roots of both carbon dioxide fluids and mud-volcanic fluids were shown to reside in the middle crust. We have compared correlative relationships for deep-seated fluids in the Caucasus with those for oils in several major oil-gas basins in Russia and in the fluid systems of Kamchatka.

We analyzed published datasets relating to the composition of glasses from melt inclusions in minerals of volcanics from the Eastern Volcanic Belt and Sredinny Range of Kamchatka. A significant difference was found between the distribution of silica concentration in the rocks and melts: intermediate and basic compositions are most common among the rocks, whereas the glasses in melt inclusions are predominantly acidic. The distribution of major and trace elements was analyzed. It was shown that the contents of some elements are environment-specific (e.g., Nb and light REEs). We identified trace element ratios in melts that most strongly correlate with the geodynamic setting.

The estimation of the degree of tectonic fragmentation for upper lithosphere following the method of Yu.V. Nechaev (2010) is based on calculations of specific lineament lengths. We used data for three regions—Northwest Caucasus, the Voronezh Anteclise, and the Malko–Petropavlovsk zone in Kamchatka—to test whether other morphometric parameters could be used: specific lengths of “weak” zones, elongation lines and water streams, as well as relief curvature. Their anomalies are confined to seismic areas and to areas of hydrothermal and magmatic activity. We show that the most information is provided by 3D models of tectonic fragmentation that incorporate specific lengths of “weak” zones and water stream lengths.

Sulfur-containing ejecta of Plinian-type eruptions can be transported to great distances in gas pores of ash particles. The mean concentration of sulfur in the rhyolite tephra of the ca. 1500 BP Opala eruption is 310 ppm. The maximum concentration can reach 800 ppm. We have found a relationship between sulfur concentration in bulk samples and grain-size composition: sulfur is mostly found in the 0.25‒0.50 mm fraction consisting of elongate ash particles with elongate gas pores 1.0‒10.0 µm long. The most likely cause why sulfur concentration depends on the structure of ash particles consists in the fact that sulfur compounds of the water-soluble complex are preserved inside gas pores; sulfur-containing compounds that have been sorbed on the surface of ash particles were removed by precipitation during the time the tephra resided in continental settings. When ash particles that contain sulfur compounds on the inner surface of gas pores come into bottom sediments during Plinian-type eruptions like that on Opala Volcano ca. 1500 BP, that can affect the geochemistry of lithogeny and rearrange the mineral phases that are sensitive to the presence of oxide-sensitive agents in the sedimentary sequence during diagenesis.

We provide the derivation of Båth’s law from Gutenberg-Richter’s law with a simple deduction through Zipf distribution for a set of data exhibiting power law scaling. It turns out that D, the difference between the magnitude of the mainshock and that of the largest aftershock (or the second largest event in the mainshock-aftershock sequence) has positive correlation with the magnitude of the mainshock. The parameters of the aftershock sequence subject to analysis, including number of samples, cutoff magnitude, and b‑value, also contribute to D and its uncertainty. The uncertainty of D is even larger associated with the ‘dragon king’ events which are the statistical outlier of the power law scaling.

This paper describes a new method for automatic preparation of a noisy seismic record for further analysis using expert information systems. The method is based on seismogram fingerprints, which, due to their concise but informative pattern, allow the development of a reliable algorithm for finding important noise characteristics. The search for the optimal cutoff frequency for a high-pass filter is especially important under conditions of partial overlap of the signal and noise spectra, when the latter have high intensity. It is precisely this difficult case that this study aims to address. The article analyzes the methodology developed here in application to several hundred records of regional earthquakes and explosions. The analysis showed that reliable results can be achieved in more than 90% of the cases. In addition, the defects and limitations of the method are mentioned, which are logical consequences of its advantages. The Appendix to this article contains a detailed description of the algorithm underlying the method.