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Similar Journals
 Seismic InstrumentsNumber of Followers: 1      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1934-7871 - ISSN (Online) 0747-9239 Published by Springer-Verlag  [2469 journals]
• Improvements in High-Precision Tiltmeter Instrument Systems Located in an
Underground Geophysical Observatory

Abstract: The paper presents the results of both theoretical and experimental studies carried out in the framework of the integrated problem on improving national systems for high-precision instrumental observations using the IPE RAS Geophysical Observatory in the Northern Caucasus. The geophysical observatory is located in the vicinity of the Mt. Elbrus in a deep underground tunnel of the Baksan Neutrino Observatory, supervised by INR RAS. Along with general information about the underground laboratory, the significant performance characteristics of the main instrument—a two-axial tiltmeter—are presented, as well as the data acquisition, processing, and storage system. The influence of natural and technogenic disturbances on the results of interpreting both tidal harmonics and other long-period variations are estimated via the developed technique to minimize the impact of a separate class of disturbances; an express estimate of the amplitude of the observed tide is performed.
PubDate: 2022-08-01

• Changes in the Fracture and Intergranular Porosity in Rock Fracture
Preparation

Abstract: The method proposed by the authors makes it possible to determine the nature of changes in two components (intergranular and fracture) of the total porosity. Changes in the fracture and intergranular porosity were investigated during fracture nucleation of sandstone samples under modeling in situ conditions. Sandstone samples were held at constant confining and pore pressure modeling in situ conditions. At the same time, only a slight decrease in the total and intergranular porosity was observed. However, only in the sample with an initially large fracture porosity was an increase in fracture porosity observed. Growth of additional axial compression reduced all types of porosity. Fracture preparation of the sample with an initially small fracture porosity was predominantly accompanied by a decrease in total and intergranular porosity and increase in fracture porosity, i.e., growth of microcracks. At the same time, during fracture preparation of a sample with an initially large value fracture porosity, an increase in total and intergranular porosity and decrease in fracture porosity were observed, which is characteristic of dilatancy processes. Differences in the fracture nucleation of sandstone samples were revealed, which indicates that their initial fracture porosity has a significant effect on them.
PubDate: 2022-08-01

• Using Microseisms for Seismic Microzoning

Abstract: The efficiency of using microseisms for seismic microzoning (SMZ) is discussed based on experimental field data in different geological conditions. The microseism method is in the list of recommendations and codes and is widely used because of its low cost. In SMZ, microseisms are used to estimate the shaking intensity increment by calculating the amplitude spectra at seismic stations and resonance characteristics of ground layers, usually in combination with other methods. Difficulties in taking into account numerous local noise sources may significantly reduce the accuracy of the results. This has to be considered when planning field works for each object (site). In some cases (high anthropogenic noise level), it is better to refrain from using the spectral amplitude ratio in the high frequency band (above 3 Hz). Calculation of intensity increments individually in the 0.5–2 and 2–3 Hz bands, taking as the final increment the maximum of both calculations, guarantees the due level of conservatism; hence, the microseism method is also applicable to critical facilities. The spectral ratio of the horizontal and vertical components of seismic motion (H/V) can be used to estimate the resonance characteristics of soils and structure of the upper part of the soil profile, in particular, the depth of the soil/bedrock boundary.
PubDate: 2022-08-01

• Features of the Structure and Formation of Dislocations in the Section of
the Mikulinsky ( $${\text{Q}}_{3}^{1}$$ ) Lacustrine Sediments of the
Dmitrov Quarry (Moscow Region)

Abstract: A complex of dislocations is described (extended gently dipping faults with a displacement of up to 1 m, dipping towards the center of the lens, steep faults with displacements of 5–20 cm), liquefaction structures (angular pseudonodules of sands in silts), near fault and near-strike-slip fault folds in the section of a large lens of the Mikulinskiy lacustrine–bog sediments (interbedded silt with a horizon of peat and clayey gyttja) of the aseismic region of the Russian Plate (Klin–Dmitrov ridge) in order to compare them with similar structures of the Baltic Shield, the seismogenicity of which is being discussed. It has been shown that the sequence was not subjected to periglacial phenomena such as glaciotectonics, glaciokarst, cryogenic deformations, the presence of which and pseudomorphism along polygonal-veined ice was noted only in the roof of the Mikulinskiy interglacial complex. A model is proposed for the formation of dislocations as a result of slumping of a silt layer with uneven subsidence of the underlying layers of peat sediments, which have been strongly compacted during lithogenesis, which explains the features of the kinematics of faults. The results showed that the dislocations of the Mikulinsky complexes of the Dmitrov quarry do not fundamentally differ from similar structures of the Baltic Shield, which confirms their lithogenic or exogenic (rather than seismotectonic) genesis in both regions. The differences in the dislocation complexes of the two regions are in the different sequence of formation of liquefaction and faults structures: in the Dmitrov section, they were formed synchronously, in the sections of the Baltic Shield, asynchronously.
PubDate: 2022-08-01

• Young Landforms Created by Earthquakes in the Foothills of the Kurai Range
(Gorny Altai)

Abstract: Structural and geomorphological studies were carried out in the foothills of the Kurai Range in southeast Gorny Altai. It is shown that the structure of the Kurai Fault Zone here is governed by north-dipping reverse faults and thrusts, along which the Kurai Range thrusts onto deposits of the Chuya and Kurai depressions. They are feathered by south-dipping backthrusts. Displacements along these fault systems lead to growth of forbergs in front of the range front and separation of smaller negative morphostructures from the Chuya and Kurai depressions. Numerous fault scarps have been revealed along the faults, which are outlets of seismic sources of paleoearthquakes to the surface. For a number of scarps, in addition to the vertical component, the strike-slip component of displacements is also read in the relief. Some fault scarps have an age of a few hundred years and arose in the sources of paleoearthquakes with minimal magnitude: MW = 6.7–7.3.
PubDate: 2022-08-01

• Natural Oscillations of a Tower-Type High-Rise Building: Modes of
Horizontal, Vertical and Rotational Oscillations According to the Standing
Wave Method and Verification of the Computational Model

Abstract: For a unique building in the form of a tower with a core of rigidity in the center, experimental studies of natural oscillations by the standing wave method with theoretical calculations based on a finite element model are performed and compared. From the experiment, ten translational horizontal modes of natural oscillations, five torsional modes of natural oscillations, and eight vertical modes of natural oscillations were identified and investigated. The finite element model is used to calculate the natural oscillations corresponding to all experimentally isolated oscillation modes. The experiment and theory are compared over the entire set of natural frequencies. Differences in natural frequencies reached 20%. After the studies, if possible, correction of the computational model ensured the difference between the experiment and the theory in terms of the values of natural frequencies of no more than 7.5%. Verification of design models of buildings using the standing wave method is an effective approach to assessing the physical condition of buildings and their seismic resistance.
PubDate: 2022-08-01

• Unification of Magnitudes for Modern Earthquakes in the Eurasian Arctic
Region

Abstract: The article presents the results of identifying correlation relationships between magnitudes of different types, calculated in international and regional seismological centers. An increase in the number of seismic stations in the Arctic in the 21st century and corresponding increase in the number of recorded earthquakes (due to a decrease in the threshold recording magnitude) has made it possible to identify quantitative relationships between magnitudes based on large samplings of earthquakes and in a wide range of magnitudes. From International Seismological Center data for 1995–2020, we obtained 30 ratios between magnitudes of different types, calculated at different seismological centers, in particular, magnitudes ranging from mb and MS 2.6 and ML = 0.8. The identified relationships will make it possible to compile an aggregated unified catalog of earthquakes for certain regions of the Arctic, which is necessary, primarily, for assessing the seismic hazard of certain areas, as well as studying low-magnitude earthquakes and clusters and swarms of such quakes.
PubDate: 2022-08-01

• Detailed Macroseismic Survey and Rational Approach to Seismic Intensity
Assessment within the Territory of a Large City: Case Study of the
Consequences of the September 21, 2020 Bystraya Earthquake in Irkutsk

Abstract: The article discusses the advisability of conducting detailed macroseismic surveys within large cities and urban agglomerations. A retrospective analysis of information about earthquakes that occurred in the past decades and were felt in Irkutsk with an intensity of I = V or higher revealed the problem of preserving and availability of primary data on earthquake effects. Processing of the macroseismic data collected using internet-based questionnaires for the Irkutsk area after the September 21, 2020 Bystraya earthquake was carried out. The usage of online questionnaires has demonstrated high efficiency and information content, and also opened up certain possibilities such as improving the method with respect to the particular conditions of East Siberia. A large number of responses from earthquake eyewitnesses makes it possible to assess the shaking intensity separately in every administrative unit of Irkutsk, which in turn contributes to an increase in the detail of documenting the earthquake macroseismic field. The results allow us to consider assessment of the shaking intensity within certain parts of Irkutsk city as more rational versus assessment for the entire territory of the city.
PubDate: 2022-08-01

• Experience of Constructing Digital Elevation Models with Unmanned Aerial
Vehicles

Abstract: This paper briefly reviews modern approaches and methods for generating digital elevation models. The focus is on photogrammetric model generation methods: photogrammetry itself relies on a series of overlapping photographic images. In our study, a camera was mounted on an unmanned aerial vehicle (UAV). We describe the major steps in generating digital elevation models, gear requirements, image capture details, and software used. Lastly, we show how we created a local digital elevation model of part of an island near the northern shore of Lake Ladoga.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030070

• Spatial Rhythms in the Data of Super-Deep Boreholes

Abstract: This article continues a study of spatial rhythmic variations of various parameters using spectral-profile analysis. This procedure has been successfully used in the Atlas of Natural Processes. In this study, manifestation of spatial rhythmic variations is considered with the example of vertical profiles composed of P-wave velocity values for three superdeep boreholes: Kola (SD-3), Vorotilov (VDB), and Ural (SD-4). Using wavelet analysis, we estimated the periodicities in the velocity variations and represented the seismoacoustic models of the SD-3, VDB, and SD-4 geological sections as a set of blocks of varying size in the upper part of the Earth’s crust. These blocks reflect the influence of different geodynamic processes at various depths. It was found that the hierarchical sequence of the average vertical sizes of the blocks corresponds to the hierarchical model of the geophysical medium. The geodynamical processes, which resulted in cyclic variations in P-wave velocities in the geological sections of the Kola (SD-3), Vorotilov (VDB), and Ural (SD-4) superdeep boreholes include: alternating epochs of volcanic activity and sedimentation, tectonic movements, impact events, penetration of intrusive bodies and amphibolite dikes in the intervals of relatively weaker rocks, and metamorphic and metasomatic alteration of rocks. Study of the sections of the superdeep boreholes can be considered, to some extent, a real-scale simulation of the crustal structure of the Earth up to large depths. Studies have shown that variations in the physical properties of crustal rocks and the hierarchical sequence of the average vertical sizes of blocks have common properties of cyclic processes involved in the “self-organization” environment.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030033

• Seismicity of the White Sea Region

Abstract: The history of instrumental observations in the northwestern East European Platform and the degree of seismological knowledge of the White Sea region is presented. The paper describes the modern seismicity of the White Sea region and considers in detail the strongest earthquake in the region for the last decades, which occurred on November 5, 2019, and, according to some features, can be thought to be unique to the region. The earthquake epicenter is located in the area of the interbasin bar dividing the Kandalaksha and Kolvitsky grabens. The calculated focal mechanism of the source shows the normal dip slip of blocks along the fault, which corresponds to he modern extension of the crust and the continuing development of the Kolvitsky graben.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030112

• Compact Laser Devices for Measuring Airborne Microparticle Concentrations
and Their Application at the Geophysical Monitoring Center of the Sadovsky
Institute of Dynamics of Geospheres, Russian Academy of Sciences

Abstract: A option of the methodology for observing PM2.5 and PM10 particle mass concentrations based on an Arduino UNO board and Sensirion SPS30 laser sensor has been developed. The measuring system built according to the technique was used in a field experiment, as well as in continuous observations at a stationary point: the Moscow Geophysical Monitoring Center of the Institute of Dynamics of Geospheres, Russian Academy of Sciences (IDG RAS). Examples of variations in the observed characteristics are given, which indicate the possibility of using the instrumental system in addition to already existing devices when observing the geophysical environment. Continuous monitoring of microparticle concentrations at the Geophysical Monitoring Center will make it possible not only to assess the degree of atmospheric pollution in the megalopolis, but also highlight certain trends, frequencies, and patterns. Such monitoring will also make it possible to reveal the contribution of various sources to the increase in microparticle concentrations, as well as the effect of pollution on different geophysical fields.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030082

• Comprehensive Assessment of Seismic Hazard and Vulnerability of
Construction Objects as a Prospect for Further Urban Planning of
Territories

Abstract: The article proposes a methodological approach to comprehensively assess the impact of seismic hazard and vulnerability of construction objects and engineering infrastructure systems on the prospects for urban planning activities. The south of Eastern Siberia and territory of the city of Irkutsk are considered as examples. We have described the main factors determining the magnitude of seismic risk, as well as possible ways to reduce vulnerability in seismically hazardous areas. The importance of detailed information on seismic impacts on an urbanized territory in the past is emphasized for making balanced and well-grounded planning decisions. It is suggested that implementation of a comprehensive approach to urban planning activities can contribute to an acceptable seismic safety level of all objects under risk.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030045

• Results of Geodynamic Observations at the Zhanazhol Field, Kazakhstan

Abstract: Repeated geodetic (ground and satellite) and gravimetric observations were carried out at the geodynamic test site at the Zhanazhol oil field (Kazakhstan) in 2010–2013. The results of leveling observations were analyzed, and local anomalies of Earth’s surface vertical displacements in fault zones were revealed. Comparison of the results of ground-based and satellite geodetic observations showed that the distribution of vertical displacements of the Earth’s surface obtained from GNSS measurements are in sharp contradiction with the releveling data. A paradoxical discrepancy between the ratio of vertical and horizontal displacements of the Earth’s surface throughout the entire field has been established. It is shown that in areas of maximum uplift or subsidence of the surface, intense horizontal displacements are observed, which contradicts the laws of geomechanics for deep objects with volumetric deformation. In these areas, horizontal displacements should have zero or minimum horizontal movement amplitude. The results of repeated leveling and gravimetric observations are compared. A regular relationship has been revealed between local subsidence of the Earth’s surface in fault zones and variations in the gravitational field. A correspondence has been established between the sign of displacements of the Earth’s surface (subsidence, uplift) and the features of development of the field. It is proposed to use geodynamic monitoring as a method for additional monitoring of field development processes.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030094

• Analysis of the Results of Long-Term Geodetic Observations at the
Ultra-Viscous Oil Field, South-East of Tatarstan

Abstract: In 2012–2018, at the geodynamic survey area of the ultraviscous oil field of PJSC Tatneft, results of measurements of formations of the Earth’s surface were obtained using discrete geometric leveling and continuous satellite receivers (GNSS). Analysis of the results made it possible to compare the vertical displacement component obtained by two completely different measurement methods. The analytical model of the deformable formation made it possible to simulate subsidence of the Earth’s surface over the entire deposit, while showing consistency with the exceedance results obtained by the leveling method. The conducted spectral analysis according to GNSS data revealed a vast number of different spectra and also allowed us to calculate the trend velocity of the Earth’s surface.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030057

• Tectonophysical Studies of Mt. Beshtau (Stavropol Krai) in Relation to the

Abstract: In the current article, we examine the tectonophysical parameters of Mt. Beshtau. A number of facts indicate that the Mt. Beshtau is developing according to the protrusive uplift type, as is the Khibiny Massif. Concentric fracturing was recorded along the periphery of the massif, which emphasizes the newest stage of development of the massif. The overwhelming number of determinations of slickensides indicate a normal-fault kinematics. Calculation of geological stress indicators allows us to suggest an extensional regime. These data lead to the conclusion that during the neotectonic stage, Mt. Beshtau is undergoing an annular subsidence with he general uplift of the massif. In the southwestern part of the faults, confined to the Skala vein system, strong seasonal radon emanation anomaly has been revealed, which is probable evidence of high-permeable rock of the massif. The results from studying this territory by different tectonophysical methods indicate the high reliability of the conclusions.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030069

• New Possibilities of Geomorphological and Tectonophysical Methods for
Analyzing Seismicity as Applied to the Northwestern Caucasus and Voronezh
Anteclise

Abstract: The paper shows the possibilities of complex morphometric analysis of the relief and computer modeling of modern geodynamics to identify seismically active areas in two different regions well studied in seismotectonic terms: the Northwestern Caucasus and the Voronezh anteclise. At the quantitative level, the majority of earthquake epicenters are associated with areas of increased values of a number of morphometric characteristics of the relief (depth of vertical dissection, steepness of slopes, density of lineaments and elongation lines, etc.). Computer modeling has been used to identify areas of possible formation of new fractures, within which 80 and 65% of earthquake epicenters of the Northwestern Caucasus and Voronezh anteclise, respectively, are located. The shares of the area of these regions are 55% (for the Northwestern Caucasus) and 36% (for the Voronezh anteclise), which indicates the informative nature of the results obtained. The research is significant, because the methods and approaches used may be in demand when delineating inferred seismically active areas of territories where detailed seismological observations have not been carried out.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030021

• Deformations, Stresses, and Strong Earthquakes in the Earth’s Crust
of Iran

Abstract: The article presents a brief overview of the currently existing ideas about the seismotectonic situation in the Earth’s crust of Iran, which is experiencing intense compression in the northeastern direction as a result of collision of the Arabian and Eurasian lithospheric plates. The survey also involved geodetic data in the form of modern GPS measurements of horizontal surface displacements. The stress-strain state of the Earth’s crust of Iran (construction of the average focal mechanism) was assessed based on data on the total set of 945 focal mechanisms of earthquakes of average strength (4.4 ≤ MW  ≤ 6.5) according to the ISC catalog, which occurred from 1975 to 2020, within 12 spatial samplings. The focal mechanisms of the strongest earthquakes in the last 50 years (MW = 6.0–7.4) for one event in each of these samplings are also considered. The calculated parameters of the average mechanisms and focal mechanisms of strong earthquakes are compared both with each other and with the surrounding tectonic situation and the distribution of deformation velocity vectors according to GPS observations. A satisfactory correspondence has been established between all the comparable values. The differences in the type of formation of the seismogenic layer of the Earth’s crust of Iran in different regions are demonstrated. These differences are manifested in different ratios of shear and thrust components in the reconstructed mean mechanism in different spatial samplings. A similar difference is noted in individual focal mechanisms of the strongest earthquakes. However, it is possible to describe the observed nature of deformation of the crust of Iran within a single concept of collisional tectonics, caused by collision of the Arabian and Eurasian plates in the last 5 Ma.
PubDate: 2022-06-01
DOI: 10.3103/S0747923922030100

• Efficiency of the Seismological Observation System at the Uda Volcanic
Complex in 2019

Abstract: The efficiency of the seismic station network on the territory of the Uda Volcanic Complex (UVC), which consists of 29 irregularly distributed instruments, was assessed. At different points of the UVC, earthquakes of different minimum energy classes were recorded with different accuracies. Calculation of the minimum energy classes for the UVC seismological network of 29 stations shows that, when the number of stations is magnified to ~30 000, such a network throughout the considered territory reliably detects earthquakes of 7.0 minimum energy classes, which corresponds to magnitudes of ~2.5. The errors in determining the earthquake epicentral coordinates in latitude (δφ) and longitude (δλ) within the network do not exceed 0.4 km. The errors in determining the depths of earthquake sources (H) in the center of such a network do not exceed 0.2 km, and within the entire territory of the UVC, 5.0 km. For these calculations, the errors in determining the travel time and propagation velocities of seismic waves were set equal to 0.1 s and 0.1 km/s, respectively, and could be both random and systematic.
PubDate: 2022-04-01
DOI: 10.3103/S0747923922020049

• Analysis of the Time Structure of Strain Processes in the Ashgabat Fault
Zone (Northern Kopet Dag)

Abstract: The paper presents the results of long-term (55 years) ground-based geodetic observations with increased spatial and temporal detail (the distance between reference points is 0.3–0.5 km, and the intervals between measurements are 1–2 months) in the Ashgabat fault zone (Northern Kopet Dag); local (with a width of 0.5 km) anomalous deformations of the Earth’s surface with average annual deformations rates of 1–3 × 10–5/year are detected. The results of comparing the velocities of vertical and horizontal displacements of the Earth’s surface in the Ashgabat fault zone with data on the modern kinematics of interaction of the Turan and Iranian plates, obtained from GNSS measurements according to the Iranian Geodetic Network, are discussed; it is shown that the rate of reduction of the Kopet Dag based on ground geodetic measurements is almost 100 times less than in GPS observations. This proves that local vertical displacement anomalies occur under conditions of a quasi-static regional stress field. Spectral analysis of long-term series of leveling observations was carried out, and the prevailing periods of anomalies of vertical displacements of the Earth’s surface were revealed. It is demonstrated that the annual harmonic dominates in the block parts of the leveling profiles. The maximum periods in the fault zone do not correspond to the annual component and have a shorter duration. It is established that the annual harmonic is associated with seasonal thermoelastic strain and local changes in the fault zone are caused by periodic changes in the pore pressure associated with the precipitation regime. A mechanism of parametric excitation of local vertical displacements of the Earth’s surface is proposed, when changes in the internal parameters of the medium (bulk elastic modulus) occur under stationary regional loading.
PubDate: 2022-04-01
DOI: 10.3103/S0747923922020062

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