One of the strongest earthquakes on August 12, 2021, MW = 8.3, near the South Sandwich Islands, where the South Sandwich Microplate is distinguished, often considered in conjunction with the Scotia Microplate, is considered. It has been established that the territory of the South Sandwich Microplate is characterized by extremely high seismic activity, the maximum values being A4.5 ≈ 3.5–3.7. The highest, A4.5 ≥ 1.0, are in the South Sandwich Islands, the eastern part of the North Scotia Range, along which the Sandwich Microplate borders the South American Plate, and, to a lesser extent, the eastern part of the South Scotia Range, along which the Sandwich Microplate borders the Antarctic Plate. The western boundary of the microplate with the Scotia Plate does not manifest itself in any way in terms of the noticeable A4.5 values recorded here. The aftershock field of the 1st day indicates that the earthquake source is elongated sub longitude, and its length is estimated as approximately 370–380 km. The nature of the aftershock process partially conform obeys the universal laws of Omori and Båth. The regular stage period of 12 days and the decay rate of the number of aftershocks p = 1.2 are comparable with similar parameters obtained earlier for a series of strong earthquakes with MW = 8.0–8.3 in the areas of Sumbawa Island of August 19, 1977; Macquarie Islands of May 23, 1989; and Balleny Islands of March 25, 1998. The strongest aftershock of the earthquake of August 12, 2021, MW = 8.3, was the aftershock that occurred on August 22, 2021 at 21:03, MW = 7.1; thus, the magnitude difference is ∆M = 1.2.

The goal of this paper is to update the information of the Automated Information Management System of the EMERCOM of Russia Unified Emergency Prevention and Response System in order to increase the reliability of the results of seismic risk assessment and ensure the safety of the population in earthquake-prone areas of the Russian Federation. The study area is Stavropol krai, where, according to general seismic zoning (GSZ) and detailed seismic zoning (DSZ), possible earthquake source (PES) zones with Мmax = 5.0, 5.5, Мmax = 6, and Мmax = 7 have been identified. The relevance of this study follows from the activation of seismicity in recent years on the considered area according to the registration by the Geophysical Survey of the Russian Academy of Sciences (GS RAS), network of seismic events within a wide range of magnitudes with М ≥ 1. The scientific novelty is due to the fact that, for the first time in the study of a single region, the results of all stages of the study are presented. Estimates of seismic hazard and parameters of the seismic intensity attenuation equation are refined on the basis of the analysis of moderate events with magnitudes in the range of M = 3.3–4.5 from the beginning of the last century to the present; the seismic risk indicators and possible consequences of scenario events for the most hazardous possible source zones are computed. For the first time, we have conducted a joint analysis of all variables. Methods of computer simulation are used to assess the risk indicators, along with the Extremum GIS developed with the participation of the authors of this article. Estimates of possible damage due to scenario earthquakes with M = 6.0 and M = 5.0 for separate large cities of Stavropol krai are obtained.

ВВЕДЕНИЕАнализ чрезвычайных ситуаций свидетельствует о том, что стихийные бедствия, связанные с опасными природными явлениями и техногенными катастрофами, представляют растущую угрозу безопасности граждан и экономики Российской Федерации.Несмотря на принимаемые меры, ущерб, возникающий при чрезвычайных ситуациях, растет, что свидетельствует об актуальности любых действий, направленных на его снижение.В связи с развитием новых компьютерных технологий появилась возможность сократить этот ущерб за счет совершенствования средств и методов автоматизированного управления спасательными операциями и превентивными мероприятиями.Для повышения эффективности управления На цио нальный центр управления в кризисных ситу а циях (НЦУКС) МЧС России внедряет Автоматизированную информационную управляющую систему (АИУС), обеспечивающую значительное повышение качества принимаемых решений о планировании превентивных мероприятий и мероприятий по оперативному реагированию в случае сильного землетрясения.Для прогноза последствий землетрясений в заблаговременном и оперативном режимах используются методы математического моделирования и калибровка моделей для оценки потерь.Одной из важнейших составных частей АИУС является подсистема оперативно-аналитической работы.Оценка параметров обстановки включена в состав функций этой подсистемы как основная, что призвано обеспечить повышение эффективности управления силами и средствами РСЧС в процессе проведения

A new generalization of Northwest Caucasus seismic hazard data is presented taking into account the influence of paleoseismological studies on the seismic hazard level. An attempt has been made to use data on paleoearthquakes for direct seismic hazard assessment by comparing, in accordance with the recurrence law, the magnitude of a strong earthquake with the estimated number of weak seismic events. A fundamentally new seismotectonic base (map of possible earthquakes source (PES) zones) has been prepared for compiling detailed seismic hazard maps of the region. Based on the map of PES zones, seismic impacts are calculated on a probabilistic basis. On the compiled maps, the northwestern and central segments of the Greater Caucasus look like a seismic hazardous area, where the level of seismic effects reaches 8.5 points on maps A and B. At the same time, compared to data from GSZ-97 maps, the results look more differentiated and overall appreciable decrease the level of seismic hazard in the region. The work is important from a methodological aspect in light of seismic risk management of this densely populated and actively developed Russian territory.

The paper presents the results of a new generalization of seismic hazard data for the northwestern and central sectors of the Greater Caucasus. A fundamentally new model of the seismotectonic basis for the seismic hazard map of the region has been prepared. The model is used to calculate seismic impact on a probabilistic basis. The work included three stages. At the first stage, seismotectonic studies were carried out, as a result of which a seismotectonic model was created and a map of zones of possible earthquake centers was compiled. At the second stage, the seismicity and seismic regime were studied in detail. The third stage calculated the frequency of seismic vibrations of various intensities in the study area based on the parameters of the macroseismic field equation, seismic activity patterns, zones of possible earthquake sources, and the slope of the earthquake frequency of the earthquakes. As a result, seismic hazard maps were compiled. The northwestern and central sectors of the Greater Caucasus look like a seismic hazardous area, where the level of seismic impacts reaches 8.5 on maps A and B. At the same time, compared to the data from the GSZ-97 and GSZ-2015 maps, the results appear more differentiated and generally significantly reduce the level of seismic hazard in the region. The study is important from the methodological aspect in light of seismic risk management of this densely populated and actively developed territory of Russia.

This paper presents the results of a seismic hazard assessment for the Magadan region (quadrangle 58.5°–66.0° N, 143.3°–157.7° E) in terms of macroseismic scale units. The extent of the research corresponds to the regional one (in the terminology framework accepted in Russia, this corresponds to the scale of the detailed seismic zoning (DSZ)). The seismic activity matrix ( A 3.3 ) is obtained and the following main seismicity parameters are estimated: the slope of the recurrence graph, the average thickness of the seismoactive layer, and depth of this layer ( h ); on the basis of the obtained results, when constructing seismic intensity maps, the focal depth we used was h = 10 km. Proceeding from the analysis of comprehensive seismological, tectonic, and geological data, 13 zones of possible earthquake sources (PES zones) with M max = 6.5, 7.0 and 7.5 were distinguished in the Magadan region . Beyond the identified zones, the background seismicity was assumed to be M max = 5.0. The study resulted in obtaining probabilistic seismic hazard maps of the Magadan region in terms of macroseismic scale intensity units, calculated for average recurrence periods of 500, 1000, and 5000 years.

The tectonic position, seismological characteristics and features of the aftershock process of the source of the strongest Near-Aleutian earthquake on July 17, 2017 on the Commander Islands with Мw = 7.8 are considered. The analysis showed that the seismic source according to the distribution of aftershock epicenters in the form of a linearly elongated narrow zone with a length of about 400 km almost completely occupied the northern slope of the Commander island elevation and was located in the Bering fault zone. It covered the whole of this seismic-generating zone up to the transverse structure to the west of the Near Islands (Attu is.). In accordance with the focal mechanisms solution and the nature of the displacements in the foci of the main shock, the strongest foreshocks and aftershocks, the shift in the source was an almost pure right-sided shift. The aftershock process of the July 17 earthquake developed quite enough inertly for an earthquake of such strength. In addition, it has two features in comparison with the aftershock processes of most of the Kuril-Kamchatka earthquakes: 1) low release of the cumulative scalar seismic moment (M0cum aft), which according to various estimates was from 0.75% to 1.0% of the seismic moment of the main shock (M0me); 2) a very slow increase in the deficit in the release of the seismic moment (M0). At the same time, the duration of the quasi-stationary phase of M0cum release in aftershocks, estimated at about ½ year and covering a significant part of the duration of the entire aftershock process of this earthquake, seems unusually long. These features of the aftershock process of the Middle Aleutian earthquake on July 17, 2017 distinguish it from the aftershock processes characteristic of most strong Kuril-Kamchatka earthquakes. In general, its source can be considered as a transform between the two Benioff zones – Aleutian and Kuril-Kamchatka, and not subduction, that is characterise the last two.

The tectonic position and overall geodynamic setting, as well as the seismological characteristics and peculiarities of the aftershock process, are considered for the source of the strongest Near Aleutian earthquake of July 17, 2017, МW = 7.8, on the Commander Islands. It is shown that in contrast to the eastern segments of the Aleutian island arc, the subduction of the Pacific lithospheric plate beneath the Commander block is not observed. The analysis has shown that, according to the distribution of the aftershock epicenters in the form of a linear elongated narrow zone with a length of about 400 km, the seismic source occupied almost entire northern slope of the Commander Island rise and spread in the Bering fault zone. It spanned the whole of this seismogenic zone up to the transverse structure west of the Near Islands (Attu islands). The focal mechanism solutions and the pattern of displacements in the sources of the main shock, as well as the strongest foreshocks and aftershocks, suggest that the slip in the source was an almost pure right-lateral shear. The aftershock process of the earthquake on July 17 developed quite feebly for an earthquake of this magnitude. Besides, it has two specific features distinguishing it from the aftershock processes of most of the Kuril-Kamchatka earthquakes: (1) a low release of the cumulative scalar seismic moment (M0cum aft), which, according to different estimates, made up from 0.75 to 1.0% of the main-event seismic moment (M0me); and (2) a very slow growth of the deficit in the release of seismic moment (M0). At the same time, the duration of the quasi-stationary phase of the M0cum release in the aftershocks, which is estimated at approximately half-a-year and which took a considerable span of the total length of the aftershock process from this earthquake, appears to be untypically long. These features of the aftershock process of the Near Island Aleutian earthquake of July 17, 2017 distinguish it from the aftershock processes peculiar to most of the strong Kuril–Kamchatka earthquakes. Overall, its source can be considered as a transform one between the two Benioff zones, the Aleutian and Kuril–Kamchatka ones, rather than as a subduction source characteristic of the last two zones.

Рассмотрены тектоническая позиция, сеймологические характеристики и особенности афтерщокового процесса очага сильнейшего Ближне-Алеутского землетрясения 17.07.2017 г. на Командорских островах с М w = 7.8. Проведенный анализ показал, что сейсмический очаг согласно распределению эпицентров афтершоков в виде линейно вытянутой узкой зоны длиной около 400 км практически полностью занял северный склон Командорского островного поднятия и разместился в зоне разлома Беринга. Он охватил всю эту сейсмогенерирующую зону вплоть до поперечной структуры к западу от Ближних островов (о. Атту). В соответствии с решениями фокальных механизмов и характером смещений в очагах главного толчка, сильнейших форшоков и афтершоков подвижка в очаге представляла собой практически чистый правосторонний сдвиг. Афтершоковый процесс землетрясения 17 июля развивался достаточно вяло для землетрясения такой силы. Кроме того, он имеет две особенности в сравнении с афтершоковыми процессами большинства Курило-Камчатских землетрясений: 1) малое высвобождение кумулятивного скалярного сейсмического момента ( M 0 cum aft ), составившее по разным оценкам от 0.75% до 1.0% от сейсмического момента главного толчка ( M 0 me ); 2) очень медленное нарастание дефицита в высвобождении сейсмического момента ( M 0 ). В то же время продолжительность квазистационарной фазы высвобождения M 0 cum в афтершоках, оцененная приблизительно в ½ года и охватившая значительную часть длительности всего афтершокового процесса этого землетрясения, представляется необычно большой. Эти особенности афтершокового процесса Ближне-Алеутского землетрясения 17.07.2017 г. отличают его от афтершоковых процессов, свойственных большинству сильных Курило-Камчатских землетрясений. В целом, его очаг можно рассматривать в качестве трансформного между двумя зонами Беньофа – Алеутской и Курило-Камчатской, а не субдукционного, характерного для двух последних.

Рассмотрены тектоническая позиция и общая геодинамическая обстановка, а также сейсмологические характеристики и особенности афтершокового процесса очага сильнейшего Ближне-Алеутского землетрясения 17.07.2017 г. на Командорских островах с М W = 7.8. Показано, что в отличие от восточных сегментов Алеутской островной дуги не наблюдается явления субдукции Тихоокеанской литосферной плиты под Командорский блок. Проведенный анализ показал, что сейсмический очаг согласно распределению эпицентров афтершоков в виде линейно вытянутой узкой зоны длиной около 400 км практически полностью занял северный склон Командорского островного поднятия и разместился в зоне разлома Беринга. Он охватил всю эту сейсмогенерирующую зону вплоть до поперечной структуры к западу от Ближних островов (о. Атту). В соответствии решениями фокальных механизмов и характером смещений в очагах главного толчка, сильнейших форшоков и афтершоков подвижка в очаге представляла собой практически чистый правосторонний сдвиг. Афтершоковый процесс землетрясения 17 июля развивался достаточно вяло для землетрясения такой силы. Кроме того, он имеет две особенности в сравнении с афтершоковыми процессами большинства Курило-Камчатских землетрясений: 1) малое высвобождение кумулятивного скалярного сейсмического момента (M 0cum aft ), составившее по разным оценкам от 0.75% до 1.0% от сейсмического момента главного толчка (M 0me ); 2) очень медленное нарастание дефицита в высвобождении сейсмического момента (M 0 ). В то же время продолжительность квазистационарной фазы высвобождения M0cum в афтершоках, оцененной приблизительно в 1/2 года и охватившей значительную часть продолжительности всего афтершокового процесса этого землетрясения, представляется необычно большой. Эти особенности афтершокового процесса Ближне-Алеутского землетрясения 17.07.2017 г. отличают его от афтершоковых процессов, свойственных большинству сильных Курило-Камчатских землетрясений. В целом, его очаг можно рассматривать в качестве трансформного между двумя зонами Беньофа-Алеутской и Курило-Камчатской, а не субдукционного, характерного для двух последних.

This paper discusses the tectonic setting, seismological characteristics, and the aftershock process for the great (MW = 7.8) Near-Islands Aleutian earthquake of July 17, 2017 off the Commander Islands. Our analysis showed that the rupture zone as inferred from the distribution of aftershock epicenters in the shape of an elongate narrow zone approximately 400 km long completely covered the north slope of the Commander Islands uplift and was confined to the Bering Fault. The rupture zone involved this entire earthquake-generating area as far as a transverse structure west of the Near Islands group (Attu Island). The fault-plane solutions and the inferred displacements in the rupture zones of the main shock and of the largest foreshocks and aftershocks revealed the rupture to be a practically pure right lateral movement. The aftershock process of the July 17 earthquake was occurring at rather a sluggish pace for such a large earthquake. In addition, the process involved two other features to distinguish it from the aftershock processes of most Kuril–Kamchatka earthquakes: (1) a low release of the cumulative scalar seismic moment (M0cum aft), which amounted to between 0.75% and 1.0% of the mainshock seismic moment (M0me), according to several estimates; and (2) a very slow increase in the deficit of seismic moment (M0) release. At the same time, the duration of the quasi-stationary phase in the release of M0cum by aftershocks, which is estimated to have lasted approximately half a year and which occupied much of the entire duration of the aftershock process for this earthquake seems to be unusually long. These features in the aftershock process of the Near-Islands Aleutian earthquake of July 17, 2017 distinguish the process from those common to most large Kuril–Kamchatka earthquakes. Overall, the rupture zone can be regarded as a transform feature between two Benioff zones (The Aleutian and the Kuril–Kamchatka ones) rather than as a subduction event, as is typical of the two latter arcs.

Based on the seismological, geodynamic, and seismotectonic data on the strongest series of earthquakes in 2009–2017 in Central Italy, which were collected by many researchers, mostly Italian, the tectonic position of these events is determined and the seismic history of the region over more than 2000 years of observations of seismic manifestations in Italy is traced in the context of the strong events of the beginning of the 21st century. The aftershock processes of these earthquakes are investigated and, as a result, the possibility of a series of strong aftershocks of the earthquake of October 30, 2016 (MW = 6.6) is predicted in advance of the actual occurrence of these events on January 18, 2017.

The characteristics of sources of the Gorkha earthquake’s mainshock (April 25, 2015, Nepal) and strongest aftershock are given. Macroseismic data and examples of seismic dislocations are provided. The course of seismic energy release during the aftershock process is analyzed. The data on seismological precursors of the mainshock and the strongest aftershock of May 12, 2015, are presented, which allowed the aftershock to be predicted in a short-term interval.

The characteristics of the foci for the main shock and strongest aftershocks of the Gorkha earthquake of April 25, 2015 in Nepal are described. The macroseismic data and examples of seismic dislocations are discussed. The progression of the release of seismic energy by the aftershock process is analyzed. The data for the geophysical and seismological precursors of the main shock and the strongest aftershock of May 12, 2015 are presented. These data allowed us to formulate the short-term forecast of this event.

Focal zone, basic shock, jerking of strongest aftershocks and progress of seismic energy release during the aftershock process of the earthquake Maule 27.02.2010 (M-W=8,8) in Chile have been analyzed. Macroseismic manifestations, tectonic position of the focus and reconstruction of acting plane position in the focus have been considered. Geophysical treatment of anomalous gravimagnetic disturbances and seismic precursors induced in variations of magnetic field and geoacoustic fields of the Earth during preparation of the basic shock and of three strongest iterative shocks on March 11-16 2010 has been done for the first time. It has been shown that application of present-day cosmic observations, which allow to analyze gravity disturbances (so far only coseismic), reflected on the Earth's surface makes possible to consider the precursors of seismic shocks of the earthquake Maule and other seismic events in a new way. Long-,middle- and short-term approaches to prognostication of strong seismic events both on land and sea have been stated.

The variations in the intensity of the global seismic process during the 20th and beginning of the 21st centuries are analyzed. It is established that the evolution of the global seismic process is marked by a trend of a certain quasi-periodicity in the release of seismic energy. The analysis of the lithospheric seismicity during 113 years has shown that this time interval accommodated three periods of seismic activation separated by two periods of relative seismic quiescence. The global seismicity of the Earth is strongly dominated by the contributions of the earthquakes in the Pacific seismic belt. A considerable effect is also provided by the northeastern margin of the Indian Ocean. The horizontal displacements of the lithospheric plates are probably responsible for the accumulation of stresses in the potential sources of the earthquakes at the interplate contacts and in the orogenic areas inside the continents. The revealed clustering of the earthquakes with M ≥ 8.3 in the narrow time intervals is probably due to the fact that the strongest seismic event that occurs at the beginning of each activation is a trigger which simultaneously causes the relaxation of a few dozen mature potential sources within 10–15 years. This interval of seismic activation is followed by a relatively quiet period of 30–35 years, when the energy for the next activation is accumulated in a series of high-magnitude sources.