Seismic Instruments最新文献

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.

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.

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.

A option of the methodology for observing PM_2.5 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.

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.

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.

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.

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.

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.

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.