Journal of Volcanology and Seismology最新文献

Simulation of a potential collapse on Koryaksky Volcano showed the most likely direction of movement for a debris avalanche. The periodic fumarolic activation of the volcano provides evidence of the circulation of meteoric waters and of favorable conditions for replacement of the bedrock in the volcanic edifice resulting in landslide deposits. Satellite data were used to study surface ground deformation. The northeastern slopes of Koryaksky are rising relative to the subsiding southwestern slopes. Recalling that Koryaksky volcano stands at a distance of 10 km from Avachinsky Volcano which has produced massive explosive debris deposits during its history, the present study is of utmost urgency. The Elizovo–Petropavlovsk agglomeration (which includes the town of Elizovo and Petropavlovsk-Kamchatsky, as well as adjacent population centers in Elizovo District), which is in immediate vicinity of Koryaksky Volcano, harbors more than a half of all population of Kamchatka, as well as facilities that produce over half of all income in the region. Consequently, the assessment of naturally occurring processes on the volcano with a view to further development of a plan to minimize their negative impact is critically important for the economy of Kamchatka.

The Evevpenta ore occurrence is situated in the northeastern part of the Central Kamchatka volcanic belt (Kamchatka Peninsula, Russia), and lies among andesitic volcanic complexes of the Neogene age. The ore bodies are veins, zones of quartz streaks, and hydrothermal breccias, accompanied by aureoles of argillization which transition into propylites at the periphery. The formation of noble-metal mineralization occurred through two phases: the hypogene (hydrothermal) phase and the hypergene phase. For the hypogene phase we have identified two mineral associations related to noble-metal mineralization: the Central area contains gold—telluride–quartz mineralization, while the Northern area hosts telluride–sulfide–quartz mineralization. The hypergene mineral association with native gold occurs within the Central area only. Based on data relating to the material composition of the ores we show that the Evevpenta ore occurrence is a typical member of epithermal reduction-alkaline or low sulfidation deposits.

This paper is concerned with sublimates sampled in 2013–2020 in the near-crater zone and on the slopes of Alaid Volcano situated in the Kuril island arc. It was found that the near-crater zone contains native metals confined to zones of acidic leaching where the original lavas and tuffs have been transformed into opal-like rocks or rocks that are sharply enriched in hydroxides of trivalent iron. These zones were found to contain native gold, palladium, silver, chrome, copper, zinc and alloys of gold and palladium, copper and zinc, copper and tungsten. The mineral nomenclature in sublimates on the Alaid slopes is broader, while the temperature of their generation is lower. The ore minerals are dominated by copper-containing ones, and sublimates have been found with vanadium-containing minerals that belong to water-containing oxides and to silicates of vanadium. We have identified two genetic types of slope sublimates: (1) minerals that have crystallized from hydrothermal or vapor-hydrothermal solutions near vents of near-surface fumaroles and (2) copper and ferrous colloform formations that were generated by settling from colloidal solutions in shallow water of drying reservoirs, including small and large pools.

This paper examines the Karymsky Volcanic Center to estimate how much volcanic and hydrothermal activity affects the chemical composition of river water. We evaluate the volumes of major and trace elements coming to the Pacific Ocean via the Karymsky River. We assess the quality of river water in compliance with the regulations for potable water, water used for household work, and in fisheries. It is shown that the formation of ion load of the river water mostly occurs by inflow of thermal waters, as well as due to water-soluble complexes of ashes discharged by Karymsky Volcano and coming to the catchment area of the river. The annual volume of dissolved material transported by the river to the Kronotsky Bay of the Pacific Ocean amounts to more than 90 kilotons.

The identification of numerous quasilinear chains of earthquakes in the epicenter field of seismicity in the Baikal region and a study of these chains showed that the chains may include, not only chains of “migrating” earthquakes, but also those arising in a random space–time distribution of earthquakes. The present statistical study of the distribution of interepicenter distances showed that “migrating” chains may be formed within clusters of seismic events, and the distribution has been investigated. We note that chains in earthquake clusters can be identified based on the distribution of time, as well as from the distribution of distances. We have found the formation of earthquake chains in the areas of the following clusters of earthquakes: the Busingol earthquakes of 1976 and 1991; the South Baikal, the Kyakhta, and the Kichera earthquakes in the Tompuda sequence, the Oldongsin and Charuoda clusters. We showed that the chains were formed during the occurrence of these clusters. The areas of concentrated chains of clustered seismicity are found to have a relationship of the positions and directivity of the chains to the strike of fault zones, to near-fault cracks, and to the orientation of nodal planes at earthquake foci.

We review empirical data and theoretical relationships to derive equations which relate the upper boundary of maximum earthquake magnitude to the volume of fluids injected by pumping water and supercritical СО₂, as well as to magmatic activity preceding volcanic eruptions. The equations can be used to predict triggered seismicity occurring during the extraction of shale gas and oil, to develop systems for extraction of geothermal energy and for burial of supercritical СО₂, as well as to assess the volumes of magma injected before eruptions of volcanoes.

This paper provides information on the volumes of ejecta discharged by lateral and summit eruptions during the period from 1932 to 1989. We show that the volumes of ejecta from lateral eruptions were larger than those of the summit eruptions for the period. We examine subsequent variations in the character of eruptions. Lateral and summit eruptions had been occurring on the volcano from 1932 to 1989, and summit eruptions alone from 1990 to 2016. Changes occurred in 2016 with the resumption of lateral eruptions on the volcano’s slopes. We note one characteristic feature, namely, all summit eruptions terminated in collapse events in the central crater. The collapse structures are characterized. The formation of the collapse structures is related to changes in the density and volume of magma as it was ascending to the ground surface. Data are provided relating to the summit eruptions of 2019–2021 and on the 2021 lateral eruption named after G.S. Gorshkov. New data are presented showing changes in the morphology of the summit crater during eruptions and collapses in the crater after the eruptions.

This paper reports results from a study of two new genetic types of diamond discovered in Kamchatka. These diamonds were formed under extra-mantle conditions, as can be inferred from the fact that there is no indication of post-crystallization annealing with the formation of aggregated nitrogen defects in them. The first of these types is defined by us as volcanic-atmoelectrogenic. This is formed directly in a volcanic ash-gas cloud due to deep-seated methane released by atmospheric electric discharges. The second genetic type of diamonds is formed at depth within a magmatic-pneumatolytic-hydrothermal ore deposit, and can be defined as the explosive-tuffisite type. The industrial potential of these types enables us to assert the discovery of a new diamondiferous province, i.e., the Kamchatka Province.

Areas where large shallow earthquakes can occur in the future are identified by considering characteristics of the attenuation field of short period shear waves in the lithosphere. A total of over 360 records of earthquakes at depths of 0–33 km have been processed; these earthquakes were recorded at the PET station from two regions enclosed in the coordinates 45.0°–50.5° N and 54.0°–56.5° N (for the sake of brevity these regions will be referred to in what follows as the southern and the northern region, respectively). In addition, for comparison purposes we used records of earthquakes made at the KGB station from the area between 52° and 54° N. We used a method based on the ratio of peak amplitudes of Sn and Pn waves. It was found that the overall attenuation in the lithosphere of the northern region is much greater than that for the southern. At the same time we note that the attenuation in both of these areas is below that in northeastern Japan. The relatively lower attenuation occurs in the rupture zones of the great earthquakes occurring in 1952 (M_w = 9.0) and in 1963 (M_w = 8.6), that is, at least 60 years ago in the southern region, while the higher attenuation occurs in the rupture zones of recent events, 1997 (M_w = 7.8), 2006 (M_w = 8.3), and 2018 (M_w = 7.3). These data are consistent with the previous inferences, namely, that typical large earthquakes in subduction zones occur in earth volumes with higher concentrations of fluids in the uppermost mantle. Following large and great earthquakes, deep fluids are rising during a few decades, producing a decrease in the attenuation of the uppermost mantle. We have identified zones of high attenuation where large (M_w ≥ 7.7) earthquakes occurred long ago. We hypothesize that active precursory processes are occurring in these zones (primarily in the Avacha Bay and east of it) before large earthquakes.

This paper summarizes available original data and material from the literature concerning our geological and geophysical knowledge of the Esmeralda submarine volcano situated at the Mariana island arc. An advanced study of the rocks dredged during the 4th and 5th cruises of the Vulkanolog research vessel yielded new information on silicate and trace element compositions of the rocks that compose the volcano. It was found that the volcanic edifice under study is composed of five rock types: basalts, basaltic andesites, dacites, gabbro, and basanites. For the first time we recovered samples of dacite and basanite that provide evidence of a broader petrochemical diversity of the Esmeralda submarine volcano compared to what has been thought previously. All dredged rocks show slightly higher concentrations of incoherent elements LILE and HFSE. Our studies enable us to classify the bulk of the dredged rocks as belonging to the association of arc ferrous tholeiites (IAB, IAT), with the composition of a single sample of alkaline basalt (basanite) plotting in the field of alkaline oceanic island basalts (OIB, OIA). The higher concentration of iron in plagioclase phenocrysts confirms the fact that the rocks are part of the high-iron tholeiitic association.