Journal of Volcanology and Seismology最新文献

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.

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.

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.