Seismic Instruments最新文献

In this paper, the geodynamic conditions of an active landslide area located along the section of the A373 highway passing through the Kamchik Pass of Uzbekistan, using modern microseismic observation methods, have been analyzed. Landslides in this region represent a serious natural threat to transport infrastructure, settlements, and economic stability. In the study, field microseismic measurements were combined with the horizontal-vertical spectral ratio (HVSR) technique to assess the dynamic characteristics of the landslide and its tendency to melt from seismic impact. Field studies were conducted using high-precision three-component seismic instruments, such as the ETNA 2 and Tromino seismometers. The recorded microseismic vibrations were processed using the Geopsy and Grilla software packages. This made it possible to determine the main dynamic parameters of the soil, such as the resonant frequency. A thematic landslide hazard map was developed, illustrating the spatial distribution of liquefaction potential and identifying zones of high seismic susceptibility. These findings demonstrate that microseismic monitoring using the HVSR method is an effective and non-invasive tool for characterizing the internal structure of landslides, evaluating their current dynamics, and supporting engineering–geological decision-making for risk mitigation. The outcomes of this research are highly relevant for seismic microzonation, landslide hazard assessment, and preventive measures for slope stabilization, contributing to the sustainable operation of strategic transportation corridors in mountainous regions.

A new vibration damping device is proposed, designed as a band-rope system with a single-acting hydraulic cylinder or a torsion bar. The device is a vibration damper and can be used on domes, rectangular frames, locators, and other infrastructure exposed to dynamic loads from seismic impacts. The methods of determining the modules of external force impacts on the protected nodes through a band-rope system are described to select the parameters of the dampers and generate internal forces to counteract vibratory motion for a torsion damper and a single-acting hydraulic cylinder damper. The formulas derived by analytical calculations make it possible to determine the effective torsion stiffness of the torsion bar and stiffness of the hydraulic cylinder spring or coefficient of resistance to the motion of the hydraulic cylinder fluid.

An overview of seismicity in 16 regions of Russia and neighboring countries in 2018–2019 is presented. Seismic monitoring of this territory was carried out by seismic networks of Russia, Azerbaijan, Armenia, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Turkmenistan, Tajikistan, Uzbekistan, and Ukraine. In most regions, the seismic process occurred in the background. In Northern Eurasia as a whole, the total seismic energy in 2018 (ΣЕ_an = 3.2 × 10¹⁶ J) remained unchanged compared to that for the previous year, and in 2019 it fell to ΣЕ_an = 0.62 × 10¹⁶ J, with annual values of released energy for 2018 and 2019 significantly lower than its average annual level for the period 2006–2017 (ΣE_an = 5.3 × 10¹⁶ J). The “Angular Uplift earthquake” on December 20, 2018 at 17:01 with MS = 7.4 (Mw_GCMT = 7.2), localized in the surface layer of the seismofocal zone of the Commander segment of the Aleutian arc with the epicenter in the Pacific Ocean was the strongest for the period 2018–2019. Maximum shaking intensity in the territory of Northern Eurasia (I = 6–7) was caused by earthquake on July 6, 2018, at 01:40 with Mw_GCMT = 6.2, h = 75 km in the seismofocal zone of the Kuril Islands–Southern Kamchatka and Katav-Ivanovsk earthquake on September 4, 2018, at 22:58 in Chelyabinsk oblast (Ural and Western Siberia region). The Katav-Ivanovsk earthquake is also unique in that it was accompanied by a significant number of aftershocks, which is the first known case for tectonic events within the Urals. In addition, it demonstrated that the natural seismic potential of the Urals exceeds the man-made component by orders of energy.

The article is dedicated to the history of development of instrumental seismic observations in the Caucasus in the first half of the 20th century. The stages of seismic observation development in the Caucasus are described, including the problems that arose during World War I and the Civil War, as well as the subsequent restoration of the seismic service in the USSR. The information on the first seismic stations in the Caucasus, their equipment, and their role in studying the seismicity of the region is summarized. Maps of the theoretical recording range of earthquakes of various magnitudes by seismic stations in the Caucasus for different periods are presented. Seismic stations of the first half of the 20th century made it possible to obtain the first data on the seismicity of the region, which made an important contribution to the study of the seismic hazard of the Caucasus region and ensuring earthquake-resistant construction on its territory; to research into the causes and conditions of earthquakes in the Caucasus with the aim of finding precursors of destructive earthquakes; and to the study of the internal structure of the region.

We suggest an approach to automatic picking of P- and S-wave arrival times when processing data from local seismological-monitoring network. A distinctive feature of this approach is that it does not attempt to train a universal neural network for processing all types of seismological data. Instead, we focus on one specific region at a time, which significantly narrows the requirements for the training dataset size and variability. An important result is the automatic quality-control tool, since it simultaneously ensures the accuracy of the accepted events as well as forms a fairly small dataset of rejected events. This small dataset can be further used for manual processing and additional neural-network training. This approach was tested on real data from two local seismological networks located in different regions. We demonstrate that a small seismological dataset can be used for training the neural network for processing seismological data from a specific region: records from 20–40 local earthquakes. For high-quality data, it is possible to pick the arrival times of P- and S-waves with an error less than 50 ms for 94 and 88% of cases, respectively. For the poor-quality dataset, it was possible to determine the arrival times of P- and S-waves with an error less than 200 ms in 82 and 73% of cases, respectively. The proposed approach makes it possible to accelerate automatic processing by reducing the required size of the training sample; the approach was implemented in stream processing for the considered seismological networks.

In recent years the global trend in seismological observations consists in increasing the number of measuring points and equipping them with broadband and highly sensitive sensors. However, this approach leads to a significant rise in the cost of measurements. One possible solution to this problem is the use of much cheaper geophones or short-period seismometers with an extended frequency range as additional sensors. The article discusses the process of synthesizing a correction filter circuit based on a biquadratic transfer function and provides schemes for broadening the frequency characteristics of sensors, including circuits for correcting the characteristics of the SM-3KV seismometer and the GS-20DX geophone in instrument design. The developed algorithm makes it possible to broaden the frequency response of the SM-3KV seismometer to the low-frequency region up to 0.02 Hz (natural frequency of 0.5 Hz) and the GS-20DX geophone to 1 Hz (natural frequency of 10 Hz).

A methodology has been developed to assess the following components of seismic risk in the territory of Armenia: buildings, population, and infrastructure. According to the methodology, risk is assessed based on data on the seismic hazard, vulnerability of buildings and structures, vulnerability of the population, and influence of a number of secondary consequences of an earthquake. The development of the methodology is based on the regulatory map of seismic hazard of the territory of the republic in 2020, the areas of seismic zones of which are taken as cells for risk assessment. First, the risk was assessed for ten cells with an area of 1.1–4.9 thousand km², then for the entire territory of Armenia. This approach is justified by the fact that the level of modern seismic hazard and the intensity of the design seismicity of buildings and existing buildings are reasonably taken into account. Particular attention is paid to buildings constructed in 1957–1989, since it was during this period of time that a large number of seismically vulnerable apartment, public, and other buildings and structures of various purposes and types were built, which significantly influence the current high seismic risk of the territory of the republic. The risk of each cell is determined based on the vulnerability of residential buildings in all populated areas (49 cities and 949 villages), the size and density of the population, infrastructure, the influence of hazardous geological phenomena activated by an earthquake, etc. These are strongly influenced by the following important factors: underestimated design seismicity, low-quality design and construction, current technical condition depending on age, illegal changes to layouts and load-bearing structures, etc. Determining the seismic vulnerability of buildings and structures and the population is quite difficult; for this reason, it is recommended to afford the leading place in the quantitative assessment of risk components to statistical data on the consequences of the 1988 Spitak earthquake and results of their analysis. For the first time, using the developed methodology, maps of the maximum seismic risk of three important components were compiled for the entire territory of Armenia.

The article considers primary coseismic deformations: the occurrence of ruptures on the surface directly related to slip in the earthquake source. The displacements at the surface rupture are estimated by the method of probabilistic fault displacement hazard analysis (PFDHA). A modification of the classical PFDHA approach for the case of diffuse seismicity is proposed and implemented. Calculations are carried out in the area of the well-studied 2003 Altai earthquake, in the epicenter of which we placed a hypothetical site on which it is necessary to estimate the displacements. This allowed us compare the obtained results with the observed surface ruptures and displacements along them. The prospects of using the method for assessing the hazard of coseismic deformations in low-active areas, where active faults are not detected or are absent, are shown.

Instrumental seismological observations were used to study the features of horizontal oscillation amplitudes along and across the crest of a mountain range during earthquakes. It is shown that the spectral amplitudes of oscillations in the direction across the ridge significantly exceed the amplitudes of oscillations along the ridge in a wide frequency range, regardless of the azimuth to the epicenter, and the frequencies of natural oscillations along and across the ridge also differ significantly.

Medium-pressure hydroelectric power plants were studied using the standing wave method. Highly accurate data on transverse, longitudinal, and vertical natural oscillations of the Nizhnekamsk and Novosibirsk hydroelectric power plants were obtained. The results allow one to use the obtained maps of standing wave amplitudes in structures to determine their block structure and to verify the calculated models of hydroelectric power plant dams, to form conclusions on the seismic resistance of objects. The results are important for filling in dam passports and for design work on creating a system of engineering and seismometric monitoring of dams.