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For the first time, a numerical comparison of the General Seismic Zoning (GSZ) maps with the effect of earthquakes that actually occurred after the publication of the maps was carried out. The area of zones of expected intensity on the GSZ map is compared with the area of isoseists from actual earthquakes. It turned out that the isoseist area is on average by an order less than expected according to the GSZ. This paper describes possible reasons for such an overestimation and proposes ways to improve seismic hazard assessments. [ABSTRACT FROM AUTHOR]

The paper presents the results of modeling the stress–strain state of the epicentral zone of the strong crustal Hanshin–Awaji earthquake, which occurred in the area of Kobe (Japan) on January 17, 1995, with a magnitude M of 6.9. In this work the author's method for modelling and analyzing the stress–strain state of the epicentral zones of crustal earthquakes was used. The geological, tectonic, and seismological data for the earthquake region are used as input data and boundary conditions for modeling. In this work it is shown that the main rupture arising at the origin of the earthquake is generated in a zone of high stress intensity at a certain ratio of the main tectonic stresses and propagates through areas of anomalously high stress concentration, causing maximum displacements in these zones. The results provide new insights into the focal mechanism of an earthquake, aimed at predicting the location and magnitude of strong crustal earthquakes in earthquake-prone areas. [ABSTRACT FROM AUTHOR]

This paper discusses the influence of high-energy electromagnetic pulses of magnetohydrodynamic generators used as transmitters when carrying out deep electrical sounding of the crust in the Garm region, Tajikistan, and North Tian Shan on the rate of seismotectonic strains in these two most seismically active regions of Central Asia. Variations of seismotectonic strains in the Garm region for 36 years of observations and in the North Tian Shan region for 22 years are considered. It has been shown for both regions that the impact of electromagnetic pulses increases the rate of seismotectonic strains 10–20 times, which leads to additional release of elastic stresses in the crust by 0.4–1.7 bar, thereby reducing the probability of the occurrence of strong earthquakes. Spatial variations of the strain rate during irradiation have been studied, and the correlation between the variations and the level of the stress in the crust has been identified. It has been shown that the variation of the strain rate during irradiation can be used as a criterion for active monitoring of the strained condition of the environment in order to forecast the locations and times of strong earthquakes. [ABSTRACT FROM AUTHOR]

comparison between values of thermal flux and the deep temperatures calculated by them and the depths of earthquake sources in three areas of the Baikal Rift Zone is made. It has been shown that during transit from the Baikal depression to the adjacent mountain massif, the thermal flux decreases almost 2–3 times. The corresponding deep temperatures decrease to a similar degree. The available data for these areas on earthquake depths show that their lower boundary both beneath the depression and the massif is located at almost the same depth, which is about 20 km. In this paper, the conclusion is made that the cause of the absence of an interrelation between thermal and seismic fields lies in the discrepancy between the measured values of thermal flux and its deep values. This discrepancy arises because conductive heat transfer in the upper part of the Earth’s crust, up to 5–10 km depth, is highly distorted by heat-and-mass transfer of ground waters. In the middle part of the crust, the difference in temperatures beneath depressions and ridges is leveled horizontally, which is reflected in almost the same depth for the basement of the seismogenerating layer beneath these main rift structures. [ABSTRACT FROM AUTHOR]

Studies have been conducted on the variations of microseismic noise recorded by broadband and short-period seismic stations in the area of South Baikal before and after the large December 9, 2020 Kudara earthquake with Mw = 5.6. Ten days before the earthquake, there was a gradual increase of oscillation amplitudes in the frequency range from 0.01 to 0.1 Hz, with an increasing background observed also during 4 days after the main shock (period from December 1, 2020 to January 12, 2021). The maximum amplitude increase is 19.5 against the background. During this time, there were recorded 48 aftershocks. The analysis of direction of particle motion in seismic waves over the reporting period showed an abrupt change in the orientation of oscillations, which is fully consistent with the azimuth for the main shock epicenter. The analysis of seismograms over the next period (from December 13) did not show similar effects in the microseismic noise field. Apparently, the microseismic noise field reflected the process of slow faulting before the earthquake and after the main shock with subsequent attenuation. [ABSTRACT FROM AUTHOR]

The results of study of the emanation response to large seismic events within the Baikal region for a year are study. In the course of this study, monitoring of the radioactivity of underground waters in the Southern Baikal region was organized and a set of the most significant earthquakes was identified. The radii of the influence zones of these seismic events were calculated, and these zones were grouped in accordance with their spatial position relative to the sampling station. Three types of emanation responses to seismic events have been identified, one of which reflects the emanation field response not to the event itself, but to the process of its preparation; i.e., it is a precursor effect. The grouping of seismic events in terms of their distance from the sampling station virtually coincides with how the events are grouped based on the type of emanation response. The results obtained show that the identification of short-term emanation precursors of strong earthquakes within the Baikal region is possible if a seismic event is strong enough and if a monitoring station is located within the zone of influence of the event. [ABSTRACT FROM AUTHOR]

On the basis of the data on perturbations in the Earth's atmosphere recorded before and after 52 significant earthquakes that occurred during the period from 1997 to 2018 in the Asian region, it is shown that the amplitudes of internal gravity waves that originated from seismically active regions can be used at the saturation threshold level for a short-term indication of upcoming seismic events. [ABSTRACT FROM AUTHOR]

This report continues a series of works by the authors on earthquake-prone areas recognition by the algorithmic system FCAZ. For the first time, successive earthquake-prone areas recognition for several magnitude thresholds in the same seismic region is conducted. This can be done by iteratively narrowing the set of recognition objects of the FCAZ system. Earthquake-prone areas for a given magnitude threshold are recognized within zones already recognized as dangerous for a smaller threshold magnitude. The reproducibility of the study is ensured by the fact that at all stages the recognition algorithm remains unchanged. Earthquakeprone areas with magnitude thresholds of М ≥ 5.5, М ≥ 5.75, and М ≥ 6.0 in the Baikal-Transbaikal region are studied successively. [ABSTRACT FROM AUTHOR]

The article presents study on generation of low frequency microseisms by infragravity waves on the southeastern coast of Sakhalin Island in Russia. It mentions the investigation of the release of stresses in the Earth's crust under the influence of microseisms to calculate influence of periodical oscillations on the tectonically active seismic zones. It adds microseisms caused by breaking of wind waves in the coastal zone have the maximum energy.

The article presents research in geophysics that traces mechanism of source formation of deep earthquakes and the transition mantle zone. A diagram of the wave forms of magnetic perturbations in the earth's magnetic field is represented. Earth's surface inclinations during a deep focus earthquake in Fiji Island, Sea of Okhotsk is diagrammatically illustrated. The article concludes that crustal seismic events can be formed by hydrogen intervention.

The article discusses the calculation of Bouguer anomalies in the northern part of Knipovich ridge, Mid-Atlantic Ridge (MAR). It says that anomalies were calculated based on the ridge's sedimentary cover and topography obtained through high frequency profiling (HFP) and continuous seismic profiling (CSP) in the bathymetric survey by the Norway Petroleum Directorate, Russian Academy of Sciences, and the Institute of Geology during R/V Akademik Nikolaj Strakhov's 24th cruise. It mentions that the strong positive Bouguer anomaly was found around Hovgaard mountain based on the anomalies' map in the area of Knipovich ridge.

The article presents a study related to geophysics, which discusses balance of energy concerning a tectonic earthquake. It states that a rational mechanical model was developed for processes of strong tectonic earthquake focuses in force interaction and contact zones between lithospheric plates as early as 1988. The study discusses determination of the part of the rock massif's elastic stress-strain energy that was accumulated during the focus evolution when earthquake occurrence is transformed into elastic seismic waves, as well as its part that is irreversibly "held" within a focus. Moreover, it explores the problem of solid mechanics, simulating the process of earthquake focus origination and evolution.

The article presents as study on the dynamic modeling of the propagation of low-frequency seismic acoustic fields in the oceanic medium. It shows the numerical modeling without the simplifications of the study wherein it notes on the propagation problems of the pulse seismic acoustic fields on the oceanic waveguides of water surface-bottom. However, the numerical solution of the differential equations in the problem is demonstrated using the grid models closest to the physical conditions of the propagation fields.

The article presents a study that analyzes seismotectonic processes based on the monitoring data of integral lithospheric parameters reflecting continuous variability of the parameters. It notes that while there are many researches into seismic hazards, the final solution that will indulge for the forecast on the future epicentral zone is still ambiguous. It asserts that the long-term experience of monitoring and analysis of geotectonic situations allow the researchers to formulate goals that require crucial factors including the continuous variations of local and integral lithospheric parameters and the fact that regional excitation of a black medium before robust earthquakes. A graph which shows the period of stable and unstable states of the medium at seismic station is also presented.

The article presents a study which examines the earthquakes distribution according to their type of motions in the Kuril-Okhotsk region in Russia and the mechanisms of earthquake sources. The study uses data from the GlobalCMT catalogue to analyze the earthquake epicenters and evaluates distribution using the three vertical projections of earthquake sources by the direction orthogonal to the Kuril-Kamchatka arc position. Result shows that earthquake sources mechanism are at depths of up to 80 kilometers (km) in the southeastern part of the regions considered close to ocean. The analysis of the epicenter locations normal to the seismic focal zone (SFZ) reveals three zones from east to west, to which faults are found.