Seismic Instruments最新文献

Comprehensive studies of seismogenic deformations in the topography, sediments, and rocks of the crystalline basement using structural-geomorphological, geophysical, and tectonophysical methods have been carried out. Based on the materials of deciphering digital elevation models, a hierarchical block-fault structure has been established, which has been partially inherited and activated in recent times and corresponds to the topographic forms and linear accumulative formations (eskers and plumes) “inscribed” in the tectonic framework. Ruptures of different kinematic types, folds, and forms of liquefaction in gravel-sand deposits have been discovered and documented within one of the massifs. The separations of reverse faults reach 1–2.2 m; those of normal faults are 1.5–4.5 m. Eight horizons with deformations have been identified, the thickness of the largest of which is ≈4 m, and the age range according to OSL dating is from 53 ± 3 cal. kyr to 41 ± 3 cal. kyr. This horizon corresponds to the parameters of the paleoearthquake of IX+ points. Other deformation horizons have a thickness from 0.1 to 0.4 m and are formed by weaker events, one of which occurred before the maximum glaciation, while six occurred later, in the Late Glacial period. Ruptures can be traced in the sediment sequences with depths of up to the first meters according to geolocation data. In the crystalline rocks in the zone of the esker and the faults controlling it, crushing zones and sliding mirrors were found, indicating a consistent activation of faults. The strike-slip and reverse character of the ruptures with a northwesterly strike line and east–northeast and southwest dip azimuths corresponding to ruptures in loose sediments and the general latest structural plan has been established.

The results of studies of the response of the soil layer to seismic impacts in the cryolithozone for frozen and thawed soils and their combinations are presented. Based on the research results, changes in seismic properties in the frozen soil massif have been analyzed and the effect of these changes on the amplitude-frequency level of seismic shaking during an earthquake has been estimated. For various variants of seismogeological models, changes in the seismic effect under the effect of high-frequency and low-frequency signals have been estimated based on mathematical modeling. It has been shown that the seismic response level of the cryolithozone soil massif containing the talik zone is determined by its location in the permafrost massif, as well as the ratio of the thicknesses of the thawed and frozen layers. The results of numerical modeling allow a reasonable approach to solving seismic microzoning problems for estimating and predicting seismic conditions in areas with a complex engineering-geocryological structure.

In this paper, features of the bottom relief of the large freshwater Lake Onega have been studied. The bottom survey was carried out using geological and geophysical methods in the waters of the Petrozavodsk Bay. As a result of processing and interpretation of the obtained field materials, it has been possible to carry out geomorphological analysis and identify characteristic types of relief. The bottom relief of the Petrozavodsk bay of Lake Onega has been found to have a heterogeneous character and to contain the following main categories: denudation-structural, accumulative-denudation glacial and fluvioglacial, and lake-nepheloid accumulative. Their genesis reflects the successive change of glacial landscapes.

This paper investigated the influence of observation system geometry on the accuracy of surface wave dispersion curve determination using the passive remote multichannel surface wave analysis (PRMASW) method. The study examined the impacts of different seismic receiver configurations, including linear and area observation systems, on the quality of dispersion imaging using synthetic data. Modeling results demonstrate that two-dimensional observation systems, such as random distribution or circular configurations, provide more accurate dispersion curve definition compared to linear systems, especially in the low-frequency region. This improved accuracy is attributed to increased spatial sampling and the ability to capture surface waves propagating in multiple directions. The paper also presents the methodology of a field experiment conducted at a seismic test site in the Novosibirsk region utilizing moving cars as controlled passive sources. The acquired data corroborate the results of the synthetic studies and demonstrate the practical applicability of the PRMASW method in field settings.

We have analyzed over 80 scientific articles from around the world on the topic of using convolutional neural networks in seismology. This review is structured as analysis of the distribution of these publications across several groups of characteristics. We have previously formulated our vision of the scientific field under consideration, focusing on such key points as the problem of the volume of data sufficient for high-quality training of neural networks; difficulties with formalizing the choice of a suitable architecture for the created neural networks; and lack of consensus among researchers on optimal methods of preliminary data preparation. Before the actual analysis of publications, the methodology of the search process is described and list of scientific databases containing links to publications from around the world is provided. The review begins with study of the long-term dynamics of publication activity on this topic, identifying specific stages when scientific progress proceeded at different speeds. Interpretation of the identified patterns can be useful in predicting the further development of this direction. Next, the distribution of the collected publications is analyzed and interpreted according to the tasks that seismologists set for the convolutional neural networks they create. As a result, the most relevant topics of our time and those that have not yet received the attention of researchers are identified. The review concludes with analysis of the problem of data preparation before loading it into the created neural networks for training and work. Different methods of data pre-preparation are analyzed by comparing their advantages and disadvantages.

The hypothesis of the thermal trigger mechanism of the effect of electric current on porous fluid-saturated rock is considered, when Joule heating of fluid (mineralized water) in pores and cracks leads to an increase in pore pressure and a decrease in the effective strength of rock. Numerical estimates of current flow in a porous fluid-saturated medium have shown that the increase in fluid temperature and, as a consequence, its pressure in the pores is several percent, which, in principle, can explain the trigger effect of electric current when the geoenvironment is in a stress–strain state close to the ultimate strength of rocks. In experiments on a uniaxial press with cylindrical samples of artificial sandstone and marble in the form of a rectangular parallelepiped of square cross-section with different porosities, the response of acoustic emissions and deformation of the sample during sessions of electrical action was demonstrated. However, when the sample was exposed to electrical current density at a level of 10^–5 A/m², which is an order of magnitude higher than the numerical estimates of the current density created in the Earth’s crust by artificial sources in field conditions, the response of acoustic emissions and the change in transverse deformation of the sample to such an effect has not been established. This allows us to conclude that the electromagnetic initiation of earthquakes when rocks are exposed to a weak electric current cannot be explained by a thermal mechanism based on Joule heating of fluids in cracks and pores of rocks.

This study assesses seismic impacts on the territory of New Tashkent through a comprehensive analysis of seismological, seismotectonic, and geological data. Potentially hazardous seismic zones were identified, and their maximum seismic potential (M_max) was estimated, leading to the construction of spatial distribution maps. Seismic impact intensity at construction sites was evaluated using the MSK-64 scale with probabilistic thresholds over a 50-year period. Engineering-geological studies, including electrical exploration and seismic microzoning, were conducted to refine local seismic conditions. MASW-based field investigations at 98 observation points were conducted and modelled in Strata software to assess seismic response. These findings contribute to improved seismic hazard assessment and risk mitigation strategies for future developments of the territory of New Tashkent.

To verify the regulatory formulas SP 286.1325800.2016, records obtained by stations of the K-NET and KiK-net strong motion networks in Japan were studied. The peak ground accelerations recorded during strong earthquakes in three magnitude ranges—6.6–6.7, 6.8–7.0, and 7.1–7.3—and calculated using the SP formulas were compared. A large scatter of experimental acceleration values for fixed magnitudes and distances from the source was obtained, associated with the dependence of peak ground accelerations on the characteristics of the source and wave propagation medium (orientation of the fault plane and distribution of displacements on it, released stress, source spectrum, frequency-dependent quality factor of the medium, local frequency-dependent amplification, soil response, surface topography and internal boundaries, etc.). Calculations using the SP regulatory formulas are based on clouds of experimental data, but significantly underestimate peak ground accelerations, especially in the focal and near zones. The SP regulatory formulas provide only approximate estimates that can be used as a reference, but in practice, for critical infrastructure, more reliable methods for assessing peak ground accelerations and other parameters of seismic impacts should be used, taking into account regional characteristics and recurrence periods of earthquakes, with elements of probabilistic analysis.

Detailed paleoseismogeological studies have been carried out in the area of the Kandalaksha low-mountain massifs on the Kola Peninsula (northeast Fennoscandian Shield). In order to identify traces of paleoearthquakes, parametrization, and dating of events, a set of methods was used, including analysis of satellite images and digital elevation models (DEM), ground-based geological and geomorphological mapping, structural and tectonophysical studies, drilling of lakes in fault zones, and selection and radiocarbon (¹⁴C) dating of paleosols. The study of various groups of seismic disturbances in topography and rock massifs (seismotectonic, seismogravitational, seismovibrational), as well as morphotectonic data, allowed us to identify the large Imandra-Kolvitsky seismotectonic zone extending over 100 km in the southwest Kola Peninsula. As a result of the research, it was found that the zone inherited from the Precambrian showed activation in the Late Glacial and Holocene. The identified areas of seismic deformations, surveyed in the area of the Luvenga Tundra key site, allowed us to establish that there were epicenter zone of seismic fault, the intensity of which ranged from IX to VIII in the Late Glacial with a decrease in the Holocene. The seismic fault has a dextral strike-slip kinematics with a thrust component, implemented in the stress field of the meridional (NNE) maximum compression and wide-latitude (WNW) stretching. New data on estimating the age of paleoearthquakes indicate the four most likely events in the Holocene (ka cal BP): (1) ≈10.4; (2) ≈7.5; (3) ≈2.8–3.0; (4) ≈0.38. The conducted research can be used to develop scientific and methodological foundations for assessing the risks of catastrophic processes, updating earthquake catalogs and databases on active faults, as well as preventing seismic hazards of platform territories.