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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. [ABSTRACT FROM AUTHOR]

This paper is a study of volcanogenic bentonite. We examine the geological structural settings of the deposits, the paleogeographic environment of sedimentation, structural and textural features of the rocks, and their diagnostic features. We have identified ore-controlling factors in the generation of volcanogenic and hydrothermal bentonite. Comparative analysis has been performed of the original volcanogenic material sampled at deposits in Russia and abroad. The Dash-Salakhly deposit (Republic of Azerbaijan) and a bentonite-bearing province on Sakhalin Island were studied to find how bentonites of different genesis were formed. These studies provide evidence that the composition of the parent material for bentonite varies in a wide range, between basalt and rhyolite. The main factor that controls the generation of bentonite is the type of the sedimentation basin and physicochemical conditions rather than the composition of the parent material. [ABSTRACT FROM AUTHOR]

Rapid and reliable tsunami forecasting for regions close to the epicenter of an undersea earthquake remains an unsolved problem. The only method of rapid tsunami hazard estimation used in Russia is the magnitude criterion. It leads to an unacceptably high percentage of false alarms. One promising new method is the modeling of the earthquake source based on the coseismic displacements recorded at coastal observation sites by Global Navigation Satellite Systems (GNSS). In this paper, we focus on the possibility of using this method for the magnitude 7–8 intraplate earthquakes, for which it is necessary to determine the rupture plane orientation. Based on numerical experiments, we obtained estimates of the accuracy and reliability of the earthquake parameters depending on the magnitude, number and relative positions of GNSS stations. We show that it is possible to determine all the main parameters of the source model of an M ≥ 7.4 earthquake based on the GNSS data, although the accuracy would not be very good. We conclude that it is advisable to use GNSS data in tsunami warning systems, at first in the testing mode. [ABSTRACT FROM AUTHOR]

This paper provides information on the structural setting and ore composition of the Nevenrekan deposit. We provide an account of the regional and local factors of mineralization control. The ore bodies are confined to the junction between regional faults and annular ruptures of a circular subsidence. The geochemical zoning of the ore field is disturbed. We show how geochemical associations are distributed in the ore zones of this deposit. The structural geological and geochemical data, as well as results from a comparison among the Au‒Ag low sulfidation (LS) deposits at the Okhotsk–Chukchi, Uda–Murgali, and Central Kamchatka volcanogenic belts, shows that the mineralization occurred in two phases. The first phase involved the generation of epithermal Au–Ag mineralization, while the second, plutogenic, phase produced intrusion-related gold system that is seen as epidotization and silicification of rocks in the ore field, as well as in the metamorphism of volcanogenic mineralization. The presence of the later mineralization phase associated with granitoids is typical of the Nevenrekan deposit as distinguished from the other Au–Ag (LS) deposits in the Evensk ore region, and makes it similar in this respect to the Karamken, Nyavlenga, and Cirotan deposits. [ABSTRACT FROM AUTHOR]

This paper presents the results from estimating the predictability of the seismicity of Shiveluch Volcano based on the earthquake catalog for the Northern Group of Kamchatka Volcanoes for 1971-1996 and 1999-2013. The mathematical model that we employed is a nonlinear second-order differential equation, while the algorithms of optimization and predictability are ours. The calculations show that seismicity can be successfully predicted for time intervals of a few weeks to a few months during phases of higher activity and for times of between a few months and a few years during phases of lower seismicity. The prediction distances are in excess of the error by factors of 20 to 50 on average. The nonlinearities in both times of higher and lower rates are close to the law of an equilateral hyperbola. We concluded that the predictability of seismicity can possibly be used in an integrated complex to predict extrusive and effusive activity and accompanying explosive activity. The prediction of major bursts of explosive activity related to failure in the existing volcanic edifice requires additional monitoring of the dome structure and the stability of the rocks that make up the dome. [ABSTRACT FROM AUTHOR]

This paper deals with the summit eruptions of 2015-2016, as well as with the 2016 subterminal eruption of Klyuchevskoi. We estimate the dimensions of the depression that was produced by a landfall in the southeastern trough of the volcano. We estimated the volume and area of landfall deposits. The observed volumes of landfalls during the terminal eruptions of 1944‒1945, 1985, and 2016 can vary within 0.006‒0.140 km3. The theoretical volumes can reach 4‒8 km3. We discuss the leading factors that cause landfalls on Klyuchevskoi. These include irreversible creep at depth, the influence of cracks and fissuring in the volcanic cone, as well as the constant intrusive activity of the volcano. Geodetic measurements revealed that the rates of sliding for several individual patches on the slopes varied between 6.7 cm/yr and 19.4 cm/yr. Video and photographic observations were used to estimate the thermal power of stable steam-gas and ash jets, volume of pyroclastics, and the volume of the erupted lava. The thermal power of the steam-gas jets for 2015 was approximately 122 × 106 kW, that of the gas-ash jets was 5.9 × 106 kW. The volume of discharged pyroclastic material was V = 0.00007 km3 for 2015 and V = 0.0003 km3 for 2016. [ABSTRACT FROM AUTHOR]

This paper presents results from a study of lava flows that were discharged by Bezymyannyi Volcano at different times, from old (about 3500 years ago) to recent ones (1985-1989). We provide detailed descriptions of the composition, structure, and petrophysical properties for the main types of constituent rocks, which are andesites and basaltic andesites. It was found that porosity is the leading factor that controls rock properties, while the effects of structural and mineralogical features are less prominent. We demonstrate the variation in the properties of rocks that compose the lava flows in relation to their ages: the older a rock is, the higher its density and strength and the lower its porosity is. [ABSTRACT FROM AUTHOR]

This paper deals with the rapid estimation of the hazard posed by strong aftershocks for Kamchatka and the Kuril Islands based on the 12-hour aftershocks, namely, their rate, time of expectation, and maximum magnitude. The data set consists of main shocks and aftershocks as reported in the Catalog of the Kamchatka Branch of the Geophysical Survey, Russian Academy of Sciences (GS RAS) for 1968-2016. We used both the Gutenberg-Richter relation and the Omori-Utsu law to find that the aftershock rates in two time intervals are connected by a relationship of proportionality, with the constant of proportionality being independent of the lowest magnitude of these earthquakes. With this property in mind, we calculated the constants of proportionality for estimating the rate of aftershocks with a magnitude above threshold values based on the data for the first 12 hours after the main shock. We have derived easily remembered rules for estimating the aftershock rates that can be expected for 5 days and for 1 month with magnitudes above a fixed value based on the 12-hour aftershock observations. We also derived empirical regression relations to estimate the magnitude of the largest aftershock that can be expected to occur during 1 year after the main shock and the time of the last aftershock to occur whose magnitude is 5.2 or greater. [ABSTRACT FROM AUTHOR]

This paper discusses results from ongoing research on long-term earthquake prediction for the Kuril-Kamchatka island arc based on the concepts of seismic gaps and the seismic cycle. We developed a forecast for the next 5 years (April 2016 through March 2021) for all segments of the earthquake-generating zone along the Kuril-Kamchatka arc. The 20 segments of the arc were analyzed to develop forecasts of the appropriate phases of the seismic cycle, a normalized parameter of the rate of small earthquakes (A), the magnitudes of moderate earthquakes that are expected with probabilities of 0.8, 0.5, and 0.15, the maximum expected magnitudes, and the probabilities of great (M ≥ 7.7) earthquakes. We discuss the seismic process in the Kuril-Kamchatka earthquake-generating zone before and after the deep-focus May 24, 2013 M 8.3 earthquake in the Sea of Okhotsk. The results corroborate the high seismic hazard in the area of Petropavlovsk-Kamchatskii and the urgent need for continuing with and expanding the ongoing work of seismic retrofitting and seismic safety enhancement. We quote practical results from applications of the method during 30 years. [ABSTRACT FROM AUTHOR]

This paper presents all direct precise leveling measurements of elevations between permanent benchmarks that stand along two lines in the Avacha Geodynamic Test Site from 1962 to 1995. These data are of special importance for future researchers. We show that the vertical strain increases as one approaches the volcanic edifice, while at the same time being oscillatory in character. The fluctuations of benchmark elevations at distances of 6-7 km from the volcano show amplitudes of -4.2 cm to +3.0 cm relative to a benchmark that is 17.4 km distant from the crater. It is hypothesized that the oscillatory character of vertical movements around the volcano is due to the varying influence of crustal stresses on the magma chamber beneath the volcano and these stresses are subject to variation in the subduction zone of the Pacific and Eurasian plates. Under these conditions the magma chamber 'operates' as a natural giant strainmeter. The leveling observations revealed subsidence on the shore of Avacha Bay in the seaport area, probably by as much as over 13 cm at the time of the large earthquake that occurred in November 1971 and whose epicenter was in the Avacha Bay at a distance of approximately 70 km from the city. [ABSTRACT FROM AUTHOR]

This paper is concerned with the geochemical features and conditions of generation for Paleozoic Au-Ag mineralization in the pre-accretionary Kedon (D) volcano-plutonic belt (KVB), which is situated within the Omolon cratonic terrane (Northeast Russia). We present new data on the compositions and concentrations of trace elements and rare-earth elements (REEs) in the host rocks and volcanogenic ores of epithermal Au-Ag fields. The ores are found to be enriched in a wide range of trace elements. The general features of the ores under study include a low level of REE concentrations, an obvious enrichment in light REEs, and considerable variations in europium anomalies, ranging from low negative to low- and strongly positive. Fluid inclusions were studied to show that the ore-forming solutions were hydrocarbonate potassium in composition. The mineral content of the fluid increases toward later, low-temperature phases of the mineralization. We found a tendency of potassium increasing from the earlier oreless quartz to productive quartz going to great depth, as well as a slow decrease in the concentrations of Na, Ca, and Cl. The productive quartz shows direct correlation in Ag-K and a reverse correlation in Ag-Na. The results indicate andesite magmas and meteoric water as the most likely sources of the fluids that have formed epithermal Au-Ag ores in the KVB deposits. [ABSTRACT FROM AUTHOR]

A deep-focus magnitude M 8.3 earthquake occurred off the Kamchatka Peninsula on May 24, 2013. This was named the 'Sea-of-Okhotsk' event. The earthquake has attracted special attention because, among other issues, it was felt uncommonly far from the epicenter, to distances of nearly 10000 km. The present paper reports its felt effects for the area around the epicenter and worldwide. We quote peak acceleration values at many stations in Kamchatka and worldwide as derived from instrumental recordings at digital seismograph stations in the Russian Far East and from those due to the Global Seismographic Network (GSN). We discuss features that are present in the instrumental records of the Sea-of-Okhotsk earthquake. [ABSTRACT FROM AUTHOR]

This paper considers the data of magnetotelluric sounding (MTS) and gravity and magnetic surveys, as well as other geological information. We describe the methods that were used in making the observations and for interpretation of MTS data. We focus on incorporating the influence of the shift effect and the coast effect. Generalized geoelectric sections are based on mean longitudinal curves, which are less subject to distortion. Transverse curves were used for fault identification. The geoelectric sections include a sedimentary-volcanogenic layer, a high ohmic crust, and a conductive lithosphere layer. They contain faults that were detected from the divergences between oriented MTS curves and other data. The deep-seated faults in the Vyvenka basin have surface expression in the form of seismotectonic discontinuities that extend for 80 and 140 km. It was found that the hypocenters of the Olyutorskii earthquake and its aftershocks were in the crustal layer above the conductive lithosphere layer. Most aftershock hypocenters are typically situated in the area of the deep fault. We discuss a possible origin of the conductive lithosphere layer and of deep faults. [ABSTRACT FROM AUTHOR]

This paper is concerned with results from the interpretation of continuous seismic profiling (CSP) data that were acquired during the 21st cruise of the R/V Pegas in 1980. The data are of relevance for the structure of conical seamounts and sea-hills at the foot of the Sea of Okhotsk margin of the Kuril island arc. The seamounts are extrusive domes (volcanoes) or magmatic diapirs with thick sedimentary caps of contrasting (at the top) and transparent (at the bottom) Cenozoic deposits. They were mostly formed in the Cenozoic, largely during Pliocene to Quaternary time; they resulted from viscous magma being emplaced into the sediments. There are also several small, buried domes with flattened bottoms that were formed by liquid magma being emplaced into the sediments (laccoliths or subvolcanoes). We also touch on questions relating to the terminology, geography, and history of submarine volcanism in the region and its relationship to the Benioff zone. [ABSTRACT FROM AUTHOR]

Work was performed in 2008-2014 on the long-term prediction of great earthquakes at the Kuril-Kamchatka arc based on patterns that are observable in the locations of the rupture zones of great earthquakes (seismic gaps) and in the seismic cycle for such earthquakes. The prediction method has been successfully developed and applied to the region since 1965 (the LTEP method). This paper presents a long-term seismic forecast for the September 2013 to August 2018 period for the Kuril-Kamchatka arc earthquake-generating zone. The forecast predicts the following quantities for 20 constituent segments: phases of the seismic cycle, the normalized rate of small earthquakes A, the magnitudes of moderate-size earthquakes to be expected with probabilities 0.8, 0.5, and 0.15, the maximum possible magnitudes and probabilities of occurrence for great (M ≥ 7.7) earthquakes in the most active depth interval, viz., 0-80 km. We also discuss the seismic process in this region for the 2008-2013 period, namely, the patterns that are observable in the locations of earthquake swarms, the values of and changes in several characteristics of the seismic process in the Kuril-Kamchatka seismic zone during the period 2008-2013, which occurred in relation with great shallow earthquakes beneath the Sea of Okhotsk (July 5, 2008, M = 7.7; August 14, 2012, M = 7.7; May 24, 2013, M = 8.3, and the giant Tohoku earthquake of March 11, 2011 with M = 9.0). The results corroborate the high seismic hazard for the area of Petropavlovsk-Kamchatskii and the urgent necessity of continuing and intensifying the ongoing work on seismic retrofitting and seismic safety. [ABSTRACT FROM AUTHOR]

This paper presents results from a study of variations in short-period shear-wave attenuation in the lithosphere of the Baikal Rift Zone (BRZ). We used earthquake records made at the Ulan-Bator station (ULN) at epicentral distances of ∼400-1300 km. The ratios of maximum amplitudes in the Sn and Pn waves were considered. We show that these ratios are on the whole considerably higher than those in other areas of Central Asia. It was found that zones of low shear wave attenuation coincide with the rupture zones of large earthquakes that occurred during the 19th and 20th centuries. We identified zones of high attenuation where no large (M∼ > 7.0) seismic events have occurred during at least 180 years. The hypothesis we propose is that precursory processes before future large earthquakes may be occurring in these zones. We discuss the question of whether wave attenuation characteristics may be related to seismicity. [ABSTRACT FROM AUTHOR]

The area of western Transbaikalia is characterized by moderate seismic activity. Nevertheless, there is historical and instrumental evidence to show that rather strong seismic events have occurred in the area and caused considerable material damage to the population centers around their epicenters. Seismological knowledge of the region is scant. The earthquake catalogs for the area and for the historical period of time need to be corrected and supplemented. The present paper considers the earthquake of October 9, 1864, which has not been included in any parametric catalog thus far. New primary data that were found in the regional periodic press were used to determine the epicenter and magnitude (M = 5.1) for the event. The earthquake of October 9, 1864 is a 'forgotten' event, but is a significant addition to the catalog for western Transbaikalia. The materials presented here can be used to assess earthquake hazard for the area, as well as to aid in the search for other unknown or 'forgotten' earthquakes. [ABSTRACT FROM AUTHOR]

Kizimen Volcano began to erupt in December 2010. The eruption was preceded by a precursory period of seismicity that lasted for 20 months. This paper discusses the space-time features of the precursory seismicity. We provide a brief description of this explosive and effusive eruption between December 2010 and March 2013. The eruption started with some explosive activity followed by extrusion of a viscous lava flow. The extrusion of viscous andesitic magma and the motion of the lava flow down the slope were accompanied by unusual seismicity in the form of the quasiperiodic occurrence of microearthquakes, the so-called drumbeat phenomenon. It is shown that the occurrence of a drumbeat was first recorded during the extrusion process at the volcano's summit. Subsequently, the drumbeat mode of activity was caused by the front of the viscous lava flow as it was moving down the slope. The dynamic parameters of the microearthquakes varied in accordance with the dimensions of the lava flow front. The motion of the main tongue of the lava flow (March to September 2011) gave rise to drumbeat I with energy classes of microearthquakes K = 3-5.5, while the second tongue, which was smaller than the first, produced drumbeat II with microearthquakes of K < 3 during its motion down the slope. In January 2013 we saw a phenomenon similar to the drumbeat that was recorded at the start of the eruption. This was caused by an obelisk being extruded at the volcano's summit. [ABSTRACT FROM AUTHOR]

This paper presents the main results from the development of the detailed seismological observation system in Kamchatka and the information on the system as of 2011. We describe the networks of seismological stations, the systems for the acquisition, storage, and processing of seismological observations and their technical, methodological, and software support. We discuss the basic characteristics of the recording channels and the system as a whole. We present the information resources of the Kamchatka seismological data bank that provide for basic research in earth sciences. In 2011, the system of seismological observation in Kamchatka was a specialized network for acquisition (recording), storage, transmission, and processing of seismic and geophysical data that provides support for the effective monitoring of seismic and volcanic activities, as well as tsunami warning. [ABSTRACT FROM AUTHOR]

This paper describes the activities of the Kamchatka Branch of the Russian Expert Council on Earthquake Prediction, Assessment of Seismic Hazard and Risk (KB REC) over a 14 year period. We provide brief information on how the KB REC functions, the methods that are used for earthquake prediction in expert assessments, forecasts, and precursors of M ≥ 6.0 Kamchatka earthquakes for the 1998-2011 period. The efficiency of prediction using several methods is estimated. [ABSTRACT FROM AUTHOR]

This paper presents a set of seismicity parameters that are estimated at the Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences based on the regional catalog data with the purpose of routine monitoring of the current seismic situation in the region. The focus is on the identification of changes in the seismic regime (seismic quiescences and seismicity increases) in earth volumes adjacent to the maturing rupture zone of a large earthquake. The techniques we use include estimation of the seismicity level for the region using the SOUS'09 scale; calculation of the variations in the slope of the recurrence relation, identification of statistically significant anomalies in the slope using the Z test, and calculation of the seismic activity A; monitoring the RTL parameter and variations in the area of seismogenic ruptures; using the Z test to detect areas of statistically significant decreases in the rate of seismicity; and identification of earthquake clusters. We furnish examples of such anomalies in these seismicity parameters prior to large earthquakes in Kamchatka. [ABSTRACT FROM AUTHOR]

This paper considers the geoecological impacts of eruptions on Karymskii Volcano and the Tokareva crater for the 1996-2008 period, which resulted in changes in (a) the relief around these edifices, (b) the discharge and composition of water in the Karymskii River and other streams in the area, and (c) the discharge and composition of gases in thermal springs. It was found that the concentration of CH previously had been abnormally high in free gases that emanate from the new Piipovskii Springs and an explanation is provided of the decrease in their concentration over time. We detected variations in the radon activity, OARn (Bq/m), in free gases that are released in the Karymskii caldera hydrothermal occurrences; the variations are consistent with those in the eruptive activity of Karymskii Volcano in 2005-2006. We describe permafrost rocks in the Karymskii caldera that favor the generation of a cryolithic zone. [ABSTRACT FROM AUTHOR]

An earthquake of magnitude M = 5.8 occurred in the upper reaches of the Uanga and Pogibi rivers in northwestern Sakhalin at 9 h 44 min WT on March 16, 2010. The event is the largest for the northwestern part of the island during the entire history of instrumental seismological observations that have been conducted on Sakhalin since 1905. A macroseismic study showed that the earthquake was felt in much of northern Sakhalin and the Amur River area. This paper presents the results from a detailed study of the seismicity in the rupture zone, the space-time distribution of aftershocks, and their relationships to the active fault zones that exist in northern Sakhalin. Some new results were obtained that concern the interrelationships between the focal mechanism and the present-day geodynamic setting. [ABSTRACT FROM AUTHOR]

Kamchatka is one of the most active volcanic regions on the planet. Large explosive volcanic eruptions, in which the ash elevates up to 8-15 km above sea level, occur here every 1.5 years. Study of eruptions precursors in order to reduce a volcanic risk for the population is an urgent problem of Volcanology. The available precursor of strong explosive eruptions of volcanoes, identified from satellite data (thermal anomaly), as well as examples of successful prediction of eruptions using this precursor, are represented in this paper. [ABSTRACT FROM AUTHOR]

This paper is a study of variations in the behavior and physico-chemical characteristics of solutions in the geyser that formed in 2008 in the place of a pulsating spring in Uzon Caldera. We describe the features of this geyser's activity in 2009 and 2010. Overheating of water is for the first time described, rising to reach100.13°C at the mouth of a geyser during an eruption. We discuss the compositions of the solutions and free gases in the geyser, the possible source depths of the solutions, and the causes of geyser generation. [ABSTRACT FROM AUTHOR]

This paper considers oil-and-gas provinces and the epochs of hydrocarbon generation in Kamchatka. We distinguish the following epochs of hydrocarbon generation: the Early Mesozoic, the Early Cretaceous, the Late Cretaceous, the Early Paleogene, the Late Paleogene, the Miocene, and the Pliocene-Quaternary. We emphasize the fact that all gas generation epochs were related to deep processes, including volcanism and hydrothermal activity. [ABSTRACT FROM AUTHOR]

A typical model of the source of a tsunami ('macroseismic source') is suggested for use in approximate estimation of maximum tsunami height using straightforward numerical modeling. In this paper the model is tested using three actual events: the 1952 North Kuril Is., 1971 Moneron, and 1994 Shikotan earthquakes, which excited considerable tsunamis at Russia's Far East coasts. Comparison of the maximum tsunami runup values as obtained in numerical experiments with observations of actual tsunamis showed that the numerical model proposed here is suitable for crude estimation of tsunami runup and tsunami waiting times for coastal population centers in the near zone of a tsunami source. [ABSTRACT FROM AUTHOR]

This paper is concerned with the Earth's electromagnetic field, a deep geoelectrical section, and the dynamics of earth conductivity. This analysis is based on MTS curves along directions that to a first approximation go along and across southern Kamchatka. It is shown that the longitudinal and transverse MTS curves are subject to the influence of local and regional geoelectrical inhomogeneities. The coast effect was studied by 3-D numerical modeling. The patterns we have found were used for interpretation of generalized MTS curves. The resulting parameters of the geoelectrical section were refined by reducing the longitudinal curve to the standard curve of apparent resistivity. The results from this interpretation are to be refined as more geoelectrical information is forthcoming. The dynamics of lithospheric conductivity were studied from data acquired during the 2005-2008 monitoring of magnetotelluric impedance in the range of periods between several hundred and several thousand seconds. The basis for the analysis was assumed to be the transverse impedance and its phase. The latter was found to exhibit anomalous bay fluctuations that might have been related to earthquakes. A possible origin of these anomalies is discussed. [ABSTRACT FROM AUTHOR]

We have studied the geological structure, material composition of the ores, and the age of the Nizhny Birkachan volcanogenic gold–silver deposit discovered recently. The ore bodies consist of veins and vein-streak zones of adularia-carbonate-quartz composition; they lie in granodiorite porphyries with U‒Pb zircon age (ID-TIMS) equal to 335 ± 2 Ma. The ores are low sulfide, low silver (Au/Ag = 1–2), with pyrite dominating the ore minerals. The Ag minerals are tennantite, Ag sulfide, native gold and silver, and hessite. From an ore vein we obtained an adularia-based 40Ar/39Ar age equal to 169 ± 4 Ma, which reflects the rejuvenation of the isotopic argon system after the emplacement of a dike of unaltered Jurassic basites that cuts through the ore body. The Nizhny Birkachan deposit has a geological structure and ore composition that are very similar to those of other Au-Ag deposits at the Kedon volcano-plutonic belt such as Kubaka and Birkachan; it was also formed in the age span 290–335 Ma. [ABSTRACT FROM AUTHOR]

In recent decades Bezymianny Volcano, Kamchatka, one of the most threatening volcanic objects of Russia, has produced an average of 1–2 short-lived, but strong, explosive–effusive eruptions per year. The most reliable source of data for identifying a precursory situation before such an eruption seems to be seismicity, with continuous data being supplied by the Kamchatka seismicity monitoring system. The formalized method developed by the present author for predicting Bezymianny eruptions based on a statistical estimation of seismicity level (SESL'09) has performed satisfactorily in real time as well, with the precursory processes before all the eight eruptions of Bezymianny in 2015–2020 being detected. Revision of all characteristics the method involves (efficiency, reliability, and validity) showed that they remained stable when new data were added. The prediction method was supplemented with a new parameter, lead time, which provides a formal procedure to estimate the expectation time for a prediction to come true. [ABSTRACT FROM AUTHOR]

This study is concerned with the structure and composition of a sheet of Cenozoic alkaline basaltoids (basanites and trachybasalts) in the upper reaches of the Kedon River, in the Kedon Uplift of the Omolon Massif. Mineralogical and geochemical data provide evidence of an intraplate, poorly differentiated type of magmas. Geochronologic isotope data (40Ar/39Ar and K-Ar methods) indicate a Late Miocene age for the eruptions in the time span between 9 and 7 ± 1 Ma. The magma source contained a considerable percentage of pyroxenites and, judging from the isotopic composition of Sr, Nd, and Pb volcanics, it is similar to the PREMA mantle component that is also characteristic for other Cenozoic alkaline basalt occurrences in Northeast Asia. The potential temperature of the mantle beneath the volcanic area is similar, judging from theoretical calculations, to the mean value of an unexcited mantle, and is consistent with the scenario of lithospheric extension initiated by remote tectonic events. [ABSTRACT FROM AUTHOR]

This study is concerned with the material composition of the ores and the ore-bearing rocks of the Nevenrekan Au–Ag deposit. We provide a petrographic description of the rocks and their metasomatic alterations within the ore field, as well as structural and textural features of the ores. Two hypogenetic phases have been identified in the mineralization. The first, epithermal, volcanogenic phase consisted in the formation of adularia–carbonate–quartz veins and host-rock metasomatites of quartz–hydromica composition, of polysulfide and gold–sulfosalt mineralization, of extensive kaolinization regions, which gives way to chlorization and carbonatization with increasing depth. The contact action of a granitoidal pluton during the second phase gave rise to Te-, Bi-, and Sn-bearing mineral parageneses, silicification, epidotization, and sericite–quartz alterations of the host rocks. We showed the sequence of formation for paragenetic associations of minerals. Our inference is that the deposit is a multiformation feature with no analogues within the Evensky ore region. The age of epithermal mineralization as determined by the 40Ar/39Ar technique using the adularia in ore veins was 79.4 ± 1.0 Ma, which is consistent with the age of several major epithermal gold–silver deposits in the Okhotsk–Chukchi volcano-plutonic belt. [ABSTRACT FROM AUTHOR]

This paper reviews the Kamchatka seismicity for a 50-year period of observation. These data were used to carry out a regionalization of Kamchatka's seismic volume and adjacent areas. In all, ten zones were identified with differing activities and origins of seismicity. A comparative analysis was carried out for the seismicity in the more active zones. We found significant differences between the structures of the southern and the northern segment in the Kamchatka part of the Kuril-Kamchatka subduction zone. Seismological data corroborated a relationship between the subduction zone and the underthrusting of the Pacific plate under the Eurasian plate. These data from the 50-year period of observation helped identify a new Koryak seismic belt that encompasses the northwestern coast of the Bering Sea. We provide a brief review of macroseismic effects due to the most significant earthquakes for the 1962-2010 period. [ABSTRACT FROM AUTHOR]

This paper discusses observations of varying tectonic forces in the Kamchatka volcanic belt around the Avacha Bay using a geomechanical sensor. These observations are used to infer an estimate of the earthquake hazard to Petropavlovsk-Kamchatskii. [ABSTRACT FROM AUTHOR]

Numerous summit and parasitic eruptions of moderate potassium magnesian and high-alumina basalts and basaltic andesites, their mineralogic and geochemical features, and the composition of in situ chilled melt inclusions in the olivine of cinder lapilli discharged by Klyuchevskoi Volcano all provide evidence of the presence of magma chambers beneath the volcano. This is also supported by a dualism in the variation of CaO and Al2O3 concentrations in olivine and clinopyroxene during crystallization. The mineralogic features in the high-alumina basalts that were discharged by all parasitic eruptions of Klyuchevskoi provide evidence of magnesian magma being emplaced from a deeper chamber into a shallow high-alumina chamber. The distribution of incoherent elements in the volcano’s magnesian and aluminiferous rocks shows that they came from a single mantle source. The geochemical and mineralogic data are in good agreement with the results of geophysical surveys that concern the structure and properties of the lithosphere beneath Klyuchevskoi. [ABSTRACT FROM AUTHOR]

We studied the distribution of tephra deposits discharged by the basaltic (52-54% SiO) explosive eruption of 1973 on Tyatya Volcano (Kunashir I., Kuril Islands). We made maps showing lines of equal tephra thickness (isopachs) and lines of maximum size of pyroclastic particles (isopleths). These data were used to find the parameters of explosive activity using the standard techniques for each of the two phases of this eruption separately. The first, phreatomagmatic, phase discharged 0.008 km of tephra during the generation of maars on the volcano's northern slope. The tephra mostly consisted of fragmented host rocks with admixtures of fragments of low vesiculated juvenile basalt. The phase lasted 20 hours, the rate of pyroclastic discharge was 2 × 10 kg/s; the eruptive plume reached heights of 4-6 km with wind speeds within 10 m/s. The second, magmatic, phase discharged 0.07 km of tephra during the generation of the Otvazhnyi scoria cone on the volcano's southeastern slope. The tephra mostly consisted of juvenile basaltic scoria. The highly explosive Plinian part of this phase lasted 36 hours, the rate of pyroclastic discharge was 8 × 10 kg/s; the eruptive plume reached heights of 6-8 km with wind speeds of 10-20 m/s. The total tephra volume discharged by the eruption was approximately 0.08 km; the total amount of ejected pyroclastic material (including the resulting monogenic edifices) was 0.11 km; the volume of erupted magma was 0.05 km (the conversion was based on 2800 kg/m density); the volcanic explosivity index, or VEI, was 3. The production rate of the Tyatya plumbing system is estimated as 3 × 10 m magma per annum. [ABSTRACT FROM AUTHOR]

This study is concerned with numerical simulation of the strain due to glaciation and glacial melting, when a magma zone (a layer containing inclusions of magma and magma cumulates) is present at the crust-mantle boundary. According to analytical solutions of this problem that involves viscous relaxation of an uncompensated depression at the place of the molten glacier, the depth to the zone of increased shear stresses beneath the depression is proportional to its width, while the relaxation duration is proportional to viscosity of the lithosphere and is a few thousand years. These fundamental estimates are corroborated by our numerical simulation. According to it, the magma zone at the Moho boundary shields the zone of increased shear stresses, limiting it from below. The maximum values (12-25 MPa) with glacial thickness 500-1000 m are reached at the top of this layer of low viscosity. The directions of maximum compression (s) as calculated for the time after the melting indicate that the magma that rises along dikes is displaced from the center of the magma lens toward its periphery. It is found that glacial unloading makes the dipping faults in the crust above the low-viscosity layer attractors for the rising magma. Glacial unloading accelerates, by factors of a few times, the magma generation in the mantle that occurs following the mechanism of adiabatic decompression, as well as facilitating the accumulation of mantle fluids in the zone of increased shear stresses at the boundary of the low viscosity layer. The magma traverses this deep fluid collector and increases the intensity and explosivity of eruptions at the beginning of an interglacial period. Our numerical simulation results are in general agreement with published data on Early Holocene volcanic eruptions that occurred after the second phase of the Late Pleistocene glaciation in Kamchatka. [ABSTRACT FROM AUTHOR]

We report determinations of the focal mechanisms for Sakhalin earthquakes during 2006 through 2015 by two different methods: the polarity of first motions using the FOCMEC program and the inversion of waveforms using the ISOLA program. We show that the resulting moment tensor solutions fairly well fit the tectonic crustal stresses for Sakhalin as determined by previous workers. We have examined the component of the moment tensor that involves a linear dipole. This is at its maximum in areas of active mud volcanism and industrial activities in oil-and-gas fields. [ABSTRACT FROM AUTHOR]

A comparative analysis of the concentrations of major oxides, trace elements, and the Nd/Nd ratios in representative sequences of volcanic and subvolcanic rocks in the western and eastern Vitim Upland has revealed petrogenetic groups with different relationships among components from lithosphere and sublithosphere sources. It is hypothesized that the initial 16-14-Ma eruptions of picrobasalts and Mg basanites in the east of the upland resulted from high-temperature melting, hence, the melting of sublithospheric peridotite and lithospheric Mg-pyroxenite mantle material with mildly and strongly depleted isotope compositions of Nd relative to the value in the primitive mantle (0.512638). The broad range of varying lava compositions in the 14-9 Ma time span was caused by 'passive' rifting in the west of the upland and by 'active' rifting in the east. The 'passive' rifting manifested itself in the melting of lithospheric material with some admixture of material from the underlying asthenosphere, while the 'active' rifting lifted deep-lying mantle material. The structural rearrangement that has been occurring in the Baikal Rift System during the last 9 Ma resulted in stopping the rifting in the area of study. Relaxation, flattening and thinning of the lithosphere beneath the east part of the system during the 1.1-0.6 Ma time span caused magma effusion with values of Nd/Nd that are typical of a moderately depleted asthenospheric source contaminated with deeper mildly depleted mantle material. [ABSTRACT FROM AUTHOR]

The seismic moment tensor (SMT) was computed for the source of the deep-focus Sea of Okhotsk earthquake of May 24, 2013 ( M = 8.3) based on two kinds of regional data: (1) coseismic displacements at GNNS stations; and (2) three-component broadband seismograms (in this case we also estimated the depth of the equivalent point source and rupture duration along with the SMT). These computations were done independently for each of the two data sets. In the first of these cases we computed the SMT using simulated static displacements due to elementary dipoles as based on the ak135 spherical earth model. In the second case we used synthetic broadband seismograms as computed for a layered, elastic, isotropic, half-space model. Both of the two inversions were carried out by original methods for calculating the simulated data. The SMT determinations that are based on the two data sets are consistent with each other and with determinations from other publications. [ABSTRACT FROM AUTHOR]

We propose a method for calculating the total mass and grain-size composition of the ash that enters the atmosphere during explosive eruptions based on direct numerical modeling of transport and precipitation of ash particles and measurements of deposited mass in the ashfall area. The solution reduces to an overdetermined problem in a single parameter, viz., discharge rate as estimated by least squares from the minimal prior information on wind field structure and discharge heights. The example we consider in this study is the explosive event of January 13, 2011 on Kizimen Volcano accompanied by emission of pyroclastic products to heights of 6-9 km a.s.l. with subsequent propagation of the downwind plume to distances on the order of a few hundred kilometers. The ultimate estimate for the emitted volume (0.68-1.67 million tons) is in overall agreement with calculations made using the isopach method along with the Fedotov nomogram based on data on the eruptive cloud height and wind velocity. It is shown that meso-scale (2-200 km) atmospheric disturbances above mountains exert the controlling influence on the conditions of transfer/deposition of ash particles; this influence should be taken into account in order to derive correct estimates for emission mass and the role of wind-caused gravity differentiation of ash material during the formation of volcanogenic deposits. [ABSTRACT FROM AUTHOR]

The results of magnetotelluric and magnetovariational studies in the Uzon caldera are considered. An analysis of magnetotelluric parameters yielded the required method of interpretation. The MTS curves were interpreted in the framework of a 2D model using the REBOCC program. Geoelectric cross sections of the caldera were constructed along two orthogonal lines. Anomalies of high electrical conductivity were identified in the sediments and in the basement and were found to be confined to the locations of geothermal springs. The higher conductivity of these anomalies is here related to the presence of highly mineralized hydrothermal solutions. Electrical conductivity was used for an approximate estimation of porosity in the sediments and basement. A subvertical zone of higher porosity was identified at depths of 1.5-3.5 km in the caldera with a connection to the channelways of fluids rising into the sediments. It is hypothesized that highly mineralized solutions are diluted with vadose water in that zone and come through fissures onto the ground surface in the form of hot springs. The totality of these data suggested a conceptual model to characterize the main features in the generation of hydrothermal springs in the Uzon caldera. [ABSTRACT FROM AUTHOR]

This study makes use of spectral models for tectonic earthquakes in application to volcano-tectonic (VT) and deep-focus long period volcanic (DL) earthquakes. For these earthquakes we adjusted the parameters of source spectra, and simultaneously, the medium where seismic waves propagate. We derived preliminary results to characterize the models of source spectra for volcanic earthquakes that occur on Klyuchevskoi Volcano. This method can also be used to estimate the attenuation parameters of seismic waves, which are important for the assessment of stress and strain in a volcanic medium. [ABSTRACT FROM AUTHOR]

The southeastern part of the North Asia craton was found to contain several circular basite-hyperbasite plutons with associated commercial platinoid placers. An analysis of geodynamic models for the formation of the region and materials of seismic tomography showed that the subduction processes that were active in the Asia-Pacific convergence zone during Mesozoic time generated a stagnant oceanic slab in the transitional mantle zone. The NE and SW boundaries of the slab appear to be coincident with transform faults. The projection of the transform fault that bounds the slab on the north-northeast coincides with the Konder-Feklistov metallogenic belt that was identified previously and its Aldan (Inagli) segment. The high platinoid potential of the circular massifs in the belt is explained by the effects of lower-mantle derivates on ascending upper-mantle plumes. [ABSTRACT FROM AUTHOR]

The Kekuknai massif was formed in the course of tectono-magmatic activity that involved the origin of a shield volcano and a caldera depression with associated emplacement of extrusions that terminated in intense post-caldera areal volcanism. The mineralogical compositions of the massif's rocks have been considered in detail. The use of previously known and newly developed indicator properties of rock-forming minerals allowed the reconstruction of the general picture of the magmatic melt evolution and conditions of rock crystallization (various fluid and water saturation levels, as well as the oxidation state of the system). Essentially island-arc or intraplate characteristics of the massif's rock compositions are found at different stages of development of a single fluid-magmatic system. Decompression evolution of the parent deep-seated basanitic magma occurred via occurrence in intermediate magma chambers of daughter magmas of trachybasalt (pre-caldera stage) or hawaiite (areal volcanism) composition. Subsequent emanate-magmatic differentiation of these melts, combined with crystallization differentiation under changing P-T-conditions, resulted in the formation of the entire diversity of the Kekuknai rocks. [ABSTRACT FROM AUTHOR]

We discuss the interpretation method and results of magnetotelluric soundings in combination with other geological and geophysical data. The interpretation method was developed by studying possible distortions in MTS curves using 3D-numerical modeling of the magnetotelluric field. Deep conductivity was studied by using longitudinal MTS curves below a period of 400 s, which are nearly unaffected by the induction effect due to marine electrical currents. Transverse curves were used to obtain more detail for the geoelectric model. Inversion of average longitudinal MTS curves resulted in a geoelectric section of the lithosphere down to a depth of 60 km. Anomalies of high conductivity in the lithosphere were detected and were found to produce certain effects in gravity and seismic velocities. MTS and seismic tomography data were used to determine the possible origin of the high conductivity anomaly and to estimate rock porosity and the concentration of magma melts. [ABSTRACT FROM AUTHOR]

Seismological Observations in Kamchatka were significantly improved due to the installation of new telemetered seismic stations near active volcanoes and the implementation of modern digital technologies for data transmission, acquisition, and processing in 1996-1998. This qualitative leap forward made it possible, not only to create an effective system for monitoring Kamchatka volcanoes and for timely and reliable assessment of the state of these volcanoes, but also to draw conclusions about volcanic hazard. The experience that was gained allowed us to make successful short-term forecasts for eight moderate explosive eruptions on Bezymyannyi Volcano of the ten that have occurred in 2004-2010, successful intermediate-term forecasts of evolving activity on Klyuchevskoi Volcano in three cases, as well as providing a successful forecast of an explosive eruption on Kizimen Volcano. [ABSTRACT FROM AUTHOR]

A summary is given and some physical properties and chemistry are described for new natural compounds of seven different classes from the deposits of fumaroles of the Great Tolbachik Fissure Eruption (1975-1976, Kamchatka), which were determined on the basis of mineralogical and crystal chemistry studies. [ABSTRACT FROM AUTHOR]

Seismicity is generally treated as an example of self-organized criticality. One alternative to this treatment may possibly be furnished by a model of seismicity that is thought of as a set of episodes of avalanching relaxation that occur randomly on a set of metastable subsystems. This model is defined by the parameter r, which specifies the hierarchical divisibility of the block structure of the medium, and by the parameter p, which specifies the probability for the incipient relaxation of a metastable state to continue. These two parameters together define the modeled value of the slope of the recurrence curve, or b-value, thus determining the mode of seismicity occurrence. This model is used to describe the seismicity in southern Sakhalin Island. In this modeling, the coefficient of hierarchical divisibility r in the block structure of the medium was assumed to be stationary and the disequilibrium parameter p was assumed to describe time-dependent variations of seismicity. We calculated models for the spatial variability of r and the time variability of p. We found abnormal growth in p during the Gornozavodsk earthquake (2006, M = 5.6) and the Nevel'sk earthquake (2007, M = 6.2). At present, we report values of p that are high (and increasing over time) in the wide area of the Poyasok isthmus. The results derived here are compared with other ideas on seismicity and with the experience that was previously gained in the area of earthquake prediction. [ABSTRACT FROM AUTHOR]

The data on geology, petrography, mineralogy and petrochemistry for Kamen volcano in the Central Kamchatka Depression are presented. A study of the volcano's rocks and comparison with rocks of neighboring active volcanoes of the Klyuchevskoy group allow the establishment of some relationships. The rocks and minerals of Kamen and Ploskie Sopky volcanoes show systematic differences in the chemistry of rocks and minerals such that they obviously could not be formed from the same primary melts. The rocks of dykes and Kamen stratovolcano on one hand and the rocks of the Klyuchevskoy Volcano on the other hand form differently directed trends on petrochemical diagrams and differ in their compositions of rock-forming minerals, such they also could not originate from the same primary melts. The lavas of the monogenetic cones of Kamen volcano and moderately magnesian basalts of Klyuchevskoy volcano are derivates of the same melts, i.e., the cones situated on the slopes of Kamen are cones of Klyuchevskoy. The rocks of Kamen and Bezymianny stratovolcanoes form a single narrow trend in all petrochemical diagrams in which the lavas of Bezymianny volcano show a silica-rich part, thus indicating a genetic relationship between these two volcanoes. [ABSTRACT FROM AUTHOR]