The paper presents an analysis of coseismic geomagnetic variations recorded by European observatories of the INTERMAGNET network during the Turkish earthquake of February 6, 2023 (Mw=7.8). To compare seismic and geomagnetic data, theoretically calculated arrival times of the primary (P) and secondary (S) waves were used, obtained within the IASP91 velocity model using the TauP package. It is shown that the calculated P wave arrival times agree with the onset of an impulsive increase in the rate of change of the horizontal component of the geomagnetic field. For additional verification of the coseismic signal origin, an azimuthal analysis of the derivatives of the horizontal geomagnetic components was performed using a polarization method. It was found that the function θ(t), which characterizes the temporal variation of the back-azimuth calculated from waveform data, exhibits a region of stable values mainly within the interval between the arrivals of the P and S waves. For most stations, the obtained azimuth values demonstrate satisfactory agreement with the geometrically calculated direction to the epicenter (the mean error is about ~11°). It is shown that rotating the horizontal components to the true azimuth leads to a concentration of signal energy in the radial component (an increase of up to ~2 times), which confirms the directional structure of the geomagnetic response. The obtained results indicate the possibility of using azimuthal analysis as an additional criterion for identifying the coseismic geomagnetic effect at remote stations.
The article presents data on the earthquake of February 8, 2025 with Mw=5.1, which occurred in the Momsky District of the Republic of Sakha (Yakutia) and was felt in the nearest settlement, Sasyr village, with an intensity of 4–5 on the MSK-64 scale. The earthquake was accompanied by numerous aftershocks. The epicenter of the Sasyr event was confined to the high-altitude Buordakh-Ulakhan-Chistay massif, which is part of the Chersky mountain system, the seismicity of which marks an interplate boundary. The earthquake resulted from strike-slip displacement along a local fault that cuts through the Buordakh massif and acts as a feathering fault relative to the main Ulakhan strike-slip fault, as indicated by the orientation of the nodal planes of the focal mechanism of the main shock and the epicentral pattern of the aftershocks.
Seismotectonic zonation of the Northwest Caucasus, taking into account the hierarchical structure of the seismogenic environment, was undertaken. At this stage, zonation was performed at the level of areal structures - large, homogeneous volumes of the seismogenic layer (domains). The study is based on the principle of mapping generalized morphotectonic variations of the manifestations of the Caucasus orogenesis, parameterizing them using a set of geological and geophysical features. The morphotectonic zonation of the Northwest Caucasus and adjacent regions is clearly and consistently expressed in the variability of the geological and geophysical parameters used, which reflect the intensity of the seismotectonic process. This demonstrates the suitability of a morphotectonic approach to mapping seismotectonic domains with parameterization based on a set of geological and geophysical features.
This paper summarizes the results of seismic monitoring of blasting operations at a limestone quarry. Data obtained during long-term monitoring allowed for a new assessment of the influence of factors affecting the amplitude of seismic waves from mass blasts. An analysis of seismograms from more than 1500 mass explosions over a 6-year period of continuous observations was conducted. It was demonstrated that at this facility there is no clear correlation between seismic wave amplitude variations and seasonal factors, which simplifies the design of mass blasts. A comparison of the seismic impact of block blasts with single-hole blasts allowed for an assessment of the impact of the accuracy of the non-electric initiation system. It was concluded that at least at this mining facility seismic wave amplitude is determined by the maximum charge mass per borehole, and improving the accuracy of the initiation system will not significantly reduce the seismic effect. The study was supported by the Ministry of Science and Higher Education of Russia within the framework of state contract, R&D project registration No. 1024032500070–8-2.7.5.
Based on the results of hydrogeodynamic and hydrogeochemical observations, an assessment of changes in the stress-strain state of the earth’s crust in Armenia was made in time and space. An analysis of the seismic regime of the Garni fault (GF) and the entire territory of Armenia was conducted. The depth of the seismically active layer of the earth’s crust was determined based on the distribution of earthquake hypocenters over the studied period and amounted to 10 km. Graphs of water level variations in hydrogeodynamic wells in connection with seismic events and crustal deformation in Armenia were obtained. A map of the hydrogeodeformation field of the earth’s crust in Armenia was compiled. The seismotectonic activity of the GF by segments was identified. Weak earthquakes constituting the geodynamic background of the GF zone were identified. When studying the geodynamics of this zone using a combination of methods, the stress of tectonic crustal blocks adjacent to the GF was taken into account. The distribution of seismicity along the conventionally marked fault segments indicates its unevenness. By comparing the obtained information with the stress measurements of each adjacent tectonic crustal block, it becomes possible to identify areas of increased geodynamic activity on the fault.
This paper describes an automatic avalanche monitoring system built on hardware and software solutions developed at the Kola Branch of the Geophysical Survey of the Russian Academy of Sciences since 2018. As of the 2025–2026 winter season, the system comprises three infrasound mini-arrays with an aperture of 150–200 meters, equipped with low-frequency microphones, located within the Khibiny mountain range. One of the arrays is additionally equipped with a seismic station. Special software developed in-house is used to automatically detect infrasound and seismic signals in array recordings. The paper describes the composition and main characteristics of the hardware of the developed system, as well as the implemented algorithms for analyzing the collected data for target signal recognition. Target signal recognition is based on the analysis of the temporal and frequency characteristics of the signals, the comparison of azimuthal estimates with a database of known avalanche catchments, and the analysis of information on regional seismicity. Statistics on snow avalanche detection for previous seasons of the system’s experimental operation are presented. Based on the analysis of the accumulated data, a conclusion is drawn regarding the zone of reliable avalanche activity detection and the volume of potentially monitored avalanches, regardless of terrain. The main limitations for transitioning to routine monitoring using infrasound control methods are the insufficient statistics on confirmed avalanche events. Therefore, at the current stage of research, it is impossible to confirm that all signals recognized by the system as avalanche-related are the result of avalanche activity. Work to accumulate statistical data on the quality of target signal recognition will continue.
The problem of assessing the sensitivity of the teleseismic network (global IMS network) to the detection of regional events is considered. It is proposed to use the method of cross-correlation of waveforms (WCC-based methods) at the stage of processing digital recordings in areas with weak seismicity and in aseismic areas where dense networks are not located usually. The lack of sufficient data in such areas makes it difficult to assess the resolution and sensitivity of the networks located in them. The use of the WCC method makes it possible to compensate for the lack of data by reducing both the amplitude and magnitude detection thresholds. This is shown by the example of the events detection in seismic region N 29 [Flinn, Engdahl, 1974], which includes the regions of the Northern Urals and the Eastern Caucasus. In these territories under consideration, there are many identical seismic groups of the IMS network at regional distances, which makes it possible to directly compare detection thresholds. The presented study analyzes the events of Kurchaloi earthquake of October 11, 2008 with Mw=5.8 aftershock sequence, recorded by the regional network of the Geophysical Survey of the Russian Academy of Sciences (GS RAS) and seismic stations of the International Monitoring System (IMS). A comparison of the regional catalog of the GS RAS, which contains the largest number of aftershocks, the teleseismic catalog of the GS RAS (MOS agency), the catalogs of the International Data Center (IDC) and the International Seismological Center (ISC) with the results of applying the cross-correlation waveforms method to the IMS data allowed us to define the detection thresholds for the Eastern Caucasus, which may be used in the study of the Northern Ural seismicity in the future.
We have been studying some seismicity characteristics in the region of South Kamchatka. It was shown that ring-shaped seismicity structures were formed in the South Kamchatka within three depth intervals: 0-33, 34-70 and 71-110 km. Similarly to the other subduction zones, the structures are characterized by threshold magnitude values (Mt1, Mt2 and Mt3 correspondingly) and also by big axis lengths (L1, L2 and L3). Epicenters of the large earthquake of August 17, 2024 and its biggest aftershocks lie on the shallow ring-shaped seismicity structure (Mt1=5.3). This effect confirms an assumption on a preparation of great earthquake in the region of the South Kamchatka. Earlier correlation dependences of Mt1 and Mt2 parameters on Mw values of major earthquakes for the west of Pacific were created. Using these dependences, we estimated magnitude of possible great earthquake in this area: Mw=8.7±0.2. The reasons for ring-shaped structures formation in different depth ranges of the subduction zones are discussed.
The possibility of implementing a medium-term earthquake forecast using the LURR method in the southern part of Sakhalin Island in certain segments of the West Sakhalin and Central Sakhalin faults is considered in light of the medium-term strong earthquake forecast mode (M=5.5 (±0.5)) currently in effect for the central and southern parts of Sakhalin Island (within the latitude range from 47°N to 49.5°N, longitude range from 141.5°E to 143°E) (Protocol No. 2 of the Sakhalin Branch of the Russian Expert Council on Earthquake Prediction dated April 9, 2025). The assessments were carried out within the framework of a two-stage approach to seismic event forecasting, when previously identified medium-term forecast zones using the calculation method are refined using short-term geophysical methods. For the short-term assessment stage, the study used data from electrotelluric potential (vertical component) and subsurface radon volumetric activity measurement sites within the medium-term forecast coverage area. It was shown that in 2025, synchronous increases in electrotelluric potentials were observed at electrotelluric potential measurement sites in the village of Kolkhoznoye (Nevelsky District) and in Yuzhno-Sakhalinsk, which characterizes periods of high seismic activity. Furthermore, anomalies were detected based on subsurface radon volumetric activity measurements at sites in Yuzhno-Sakhalinsk and Firsovo before the earthquake activation in late June 2025 (a double earthquake near Aniva and Bykov). Updated LURR data (July 2025) showed that the only anomalies over the past five years were recorded in mid-2023. Although this study does not identify short-term precursors, it does provide additional data on the persistence of unstable conditions and confirms the relevance of the proposed medium-term forecast based on direct geophysical measurements.
Thе brief description of the seismicity of the Batken region and adjacent areas is given. The methodology and stages of a probabilistic assessment of seismic hazard for this territory using the OpenQuakeEngine software are considered. The results are presented in the peak and spectral ground accelerations and disaggregation parameters.
The presented article brings the reader to the final part of the development of the proposed neural network expert system for automatic classification of seismic events by their seismogram. The fundamental principles of the system were described in previous publications of the series. Here are the results of its testing for a set of characteristics related to the recognized events, conditions of their occurrence, features of registration, principles of processing records and methods of their analysis. The weaknesses and strengths of the methods used are shown. Ways to improve the quality, accuracy and speed of the expert system are outlined. Possibilities of complicating the set of characteristics are proposed, the classification of records by which can be made, for example, by tectonic conditions in the earthquake source.
This paper explores the potential for diagnosing the structural integrity of large hydraulic structures, such as the Sayano-Shushenskaya HPP (SSHPP), through the analysis of changes in their natural frequencies. It describes how seismographs located away from the object under study can be used to record microseismic vibrations and convert them into spectrograms. Using data collected between 2016 and 2024, it analyses the dependence of the fourth mode frequency of dam vibrations on the fill level and ambient temperature of the dam. The analysis shows that the fill level significantly affects the natural frequency of the dam, while the effect of temperature demonstrates ambiguous dependencies that require further study. The paper demonstrates that abnormal changes in the natural frequency of the dam occur at the limit values of the reservoir filling, which can be associated with defects revealed when significant hydrostatic pressure arises. Graphs comparing the frequency with deformation graphs obtained directly on the dam are provided. The importance of taking into account various factors that may influence changes in natural frequencies is emphasized. The method under consideration has shown good potential and should be tested on several structures in future.
The article presents the results of the analysis of macroseismic and instrumental data on a moderate earthquake (KR=12.7, mb=4.7) recorded on November 10, 2024 at 12h11m in the Eastern Sayan Mountains. Macroseismic data for this seismic event were collected using an online questionnaire. A total of 353 responses were received from respondents, 206 of which were from Irkutsk. Instrumental data were obtained by stations of the regional network, as well as by a temporary engineering seismometric station in one of the buildings of Secondary School No. 64 in Irkutsk, where an assessment of the technical condition of the building was being carried out at the time of the earthquake. The old school building was put into operation in 1955, the new one – in 2020. The survey was carried out by recording microseisms using “Baikal” equipment with A1638 seismometers. As a result, it was established that the new building of School No. 64 is in good technical condition. The old building, built in 1955, requires a thorough additional survey in order to assess its dynamic parameters.
A new seismological data information system has been developed and is being implemented at the Sakhalin Branch of GS RAS. The goal of the system is to consolidate all data obtained from seismic monitoring in the Sakhalin Region, Primorsky Krai, Khabarovsk Krai, Amur Oblast, as well as the northwestern Pacific Ocean, the Sea of Okhotsk, and the Sea of Japan into a single information space. The new expanded version is called “The Far East Region Seismicity Monitoring Database”. The article describes the database’s organizational principles, functionality and key features. Currently, the database includes a number of functions: automatic email sending, advanced map queries, automated query-based reports and near-real-time monitoring tools for emergency services. The main result is the compilation of an operational earthquake catalog and the provision of operational data to interested organizations.
The article is devoted to the assessment of the seismicity level of the Baikal and Transbaikal regions. Since seismicity in the region is heterogeneous, we assessed the seismicity level using the SESL’09 method for individual regions, using empirical distribution functions of the total released seismic energy. The use of such an approach is justified in cases of qualitative comparison of seismic regime parameters of different areas, when the same absolute value of seismic energy can be abnormally high for one area and abnormally low for another. For this purpose, the study area was divided into zones based on geomorphological and seismological data. For the selected areas and the study area as a whole, the total graphs of conditional elastic deformation release (according to Benioff), empirical distribution functions of seismic energy in a three-year time window, graphs of variations in released energy and the number of earthquakes were analyzed. As a result, the seismicity level in 2020-2022 was defined as background increased for the entire study area and the Khuvsgul-Tunkinsky and South Baikal regions, and background average for the remaining six regions. The magnitude (energy class) of earthquakes that can be called significant (strong) for each region was identified. The epicentral regions of the Baikal and Transbaikal regions were divided into three groups with high, medium and low seismic activity, depending on the seismicity parameters obtained in this work (Kmax, density, ranges of extremes of possible released energy and the average background level, the slope of the release graph of conditional elastic deformations).
Instrumental and macroseismic data on the earthquake of February 12, 2025, with the epicenter in the Black Sea near Tuapse at 13:40 with h=11 km, Mw=3.3 are presented. The earthquake parameters were determined based on instrumental data from regional seismic station networks of the GS RAS, the Crimean Center, and Georgia. Source spectra were calculated based on the records of regional seismic stations of the GS RAS and the spectral parameters were determined: seismic moment M0, stress drops Δσ and rupture radius R. In tectonic terms, the earthquake under study occurred in the Tuapse Trough zone in the Black Sea ESZ with Mmax=6.0. The focal mechanism of the earthquake was defined as a normal fault with a right-lateral strike-slip. Macroseismic data collection was carried out; the maximum intensity in the nearest populated area to the epicenter, the city of Tuapse, was 4 points on the seismic intensity scale – national standards of Russia GOST R 57546-2017.
Instrumental and macroseismic data on the Tajikabad earthquake of April 13, 2025 with MS=Mw=5.9, which occurred in the northeast of the Tajik depression, are analyzed. In a number of settlements in the Surkhob River valley, at distances of 7–25 km from the epicenter, the earthquake caused destructive consequences corresponding to 7-point intensity by the SHSI-17 scale (Russian seismic intensity scale, State Standard 57546-2017). The intensity at the epicenter, calculated using the macroseismic field equation with coefficients for the Tajik depression, was I0=8. The earthquake was recorded by nine stationary seismic stations of the Geophysical Service of the National Academy of Sciences of Tajikistan and hundreds stations of various international seismological centers around the world. The earthquake epicenter was found to be confined to the northeastern-trending Yafuch fault, with the orientation and dip of which one of the nodal planes of the focal mechanism coincides. Records of strong ground movements at 44 seismic stations in Central Asia were analyzed. The instrumental intensity at 44 strong motion recording points in Tajikistan and neighboring countries was estimated based on acceleration amplitudes, and in most cases it turned out to be lower than the observed intensity. This may be due to the installation of sensors at bedrock outcrops, which corresponds to category I soils, as opposed to category II and III soils in populated areas. The earthquake was accompanied by an intensive aftershock process: within the week since the main shock, 92 aftershocks with M=2.6–4.7 and many weaker ones were registered and processed. The largest aftershocks were noticeable.
An express analysis of two perceptible earthquakes that occurred in April 2025 in the Khabarovsk region on April 2, 2025 at 05:48 with ML=3.9 and on April 14, 2025 at 11:32 with ML=3.3. The earthquake parameters were determined in real time by the duty shift of the Yuzhno-Sakhalinsk Regional Seismic Center based on the data from the regional network of the Sakhalin Branch GS RAS and were refined in the Department of consolidated seismic data processing of the Sakhalin Branch GS RAS using the data from the stations of both the regional network and the local network of the south of Sakhalin Island, as well as the stations of the network of the Yakut Branch GS RAS. The epicenters of both earthquakes are confined to the Middle Amur and Coastal Primorsko-Priamurskaya zones of the Sikhote-Alin region of Primorye and Priamurye, the seismicity of which is extremely low, the last perceptible earthquakes in these zones occurred 100 and 50 years ago. Focal mechanisms of both earthquakes have been constructed. Macroseismic data have been collected and a map of the manifestations of the earthquake on April 14 in different parts of Komsomolsk-on-Amur with an intensity of 2 to 4 points has been compiled, which clarifies the clearly underestimated assessment of emergency services (1–2 points).
Shallow ring-shaped seismicity structures prior to 23 large and great earthquakes were picked out in different subduction zones. In many cases essential growth of the total energy of earthquakes, forming ring-shaped structures was observed directly prior to such events. The data on time duration intervals ΔТp, in which such effect takes place, were adduced for earthquakes with magnitudes from 7.0 to 9.1 in different subduction zones. We obtained a correlation dependence of ΔТp on magnitudes of large earthquakes, before which ring-shaped structures are forming. Big ring-shaped structure was picked out in the region of South Kamchatka. That gave a possibility to predict a preparation of great earthquake here. Using of the correlation dependence allows us to specify noticably expected time of such event. The data obtained can be used for a purpose of mid-term prognosis of large and great earthquakes.
Instrumental and macroseismic data are presented on the earthquake on August 26, 2025 at 20:33 (UTC) with ML=5.6, h=78 km with the epicenter in the shelf part of the Caspian Sea. The earthquake parameters were determined based on instrumental data from the network of regional seismic stations of the North Caucasus of the GS RAS and the networks of the nearest surroundings. The focal mechanism solution was obtained based on the signs of the first arrival of P-waves at 95 seismic stations. It was found that the focal point was a normal fault along one of the nodal planes of steep dip and sublatitudinal strike. In tectonic terms, the earthquake under study occurred in the middle part of the Caspian Sea, where earthquakes of similar depth and mechanism had occurred before, for example, on April 22, 2000, 08:46 (UTC) with mb=5.1 (MOS). According to preliminary data, the earthquake was felt in Novokayakent, Makhachkala, Kaspiysk, Kizilyurt, Derbent, Izberbash, Dagestanskiye Ogni, Tarki, Kyakhulai with an intensity of 4–5 points, Samur – 4 points, Bavtugay, Khasavyurt – 3–4 points, Grozny, Gudermes – 3 points, Astrakhan – 2 points.
