Seismic Instruments最新文献

The article provides an example of an instrumental solution for expanding the frequency band of the sensor into the low-frequency region using the SM-3KV short-period seismometer. The correction circuit is built on two stages of integrators on operational amplifiers. The developed prototype SM-3KV-cor was tested in laboratory and field conditions. Analysis of records of explosions and earthquakes showed that the developed scheme can be used when conducting seismic monitoring at frequencies above 0.06 Hz. When compared with data from a broadband seismometer, it is shown that the SM-3KV-cor can be used to reconstruct the velocity features of the Earth’s crust near the installation site of a seismic station based on the construction of receiver functions. When analyzing the total records of P-S converted waves, a phase was identified from the lower boundary of the phase transition zone of the upper mantle at a depth of about 660 km, which suggests the possibility of using the SM-3KV-cor sensor also to analyze the features of the phase transition zone.

Destructive earthquakes (intensity 9 on the EMS-98 scale, or M = 7.0–7.5), especially in developing countries, have a strong impact on the health and living conditions of people. They cause great loss of life both during and after an earthquake, since hazards to life and health are associated both with the destruction from the earthquake and with the living conditions that develop in its zone of influence. The main aim of the article is to highlight the most complete list of groups of factors affecting human health from a destructive earthquake and to identify the characteristics of these effects, including the most typical diseases. To conduct research and obtain generalizing conclusions, three multilaterally and in-depth studied earthquakes with severe consequences were selected. For the first time, the most complete list of the main factors of a destructive earthquake affecting people’s health has been compiled, which, according to their genesis, are divided into five groups. Typical diseases are predicted in different zones of damage to buildings and structures. They are presented in a table, indicating some parameters of their distribution area and the most characteristic diseases that have arisen according to the International Classification of Diseases ICD-10. A map of zones of three important interrelated consequences of earthquakes (damage to buildings, groups of impact factors, severity of probable diseases) has been compiled. Average graphs of changes in the level of impact of groups of earthquake factors on people’s health as a function of time are presented, as well as methodological recommendations and assessment data for quantitative calculations of the consequences of an earthquake.

Synchronous recordings of the readings of two torsion pendulums located at a distance of about 3000 km from each other are considered: in the settlement of Mosrentgen (New Moscow) and Novosibirsk. The duration of joint records is 350 days, from August 19, 2022, to August 4, 2023. The hypothesis is considered that the excitation of oscillations of torsional pendulums precedes strong seismic events, including those whose epicenters are located far from the location of measurements. The presence of two synchronous measurement points makes it possible to eliminate the influence of intense local interference by assessing the coherence spectrum in a moving time window. The sequence of times of occurrence of maximum coherences in time windows of 1 h duration is analyzed together with the sequence of seismic events with a magnitude of at least 5 using a parametric model of interacting point processes (influence matrix method). The influence matrix method makes it possible to give a quantitative measure of the influence of two random time sequences on each other. The estimate of the correlation function between the daily values of the logarithms of seismic energy emissions exceeding a given threshold and the daily average maximum values of the elements of the influence matrix has a strong asymmetry, which gives grounds for quantitative confirmation of the hypothesis that the excitation of torsion pendulums precedes strong earthquakes with an average delay time of about 20 days.

The differences in the metrological support, problem statement, and practice of conducting measurements and using data in a typical physical experiment and geophysical monitoring are discussed. The strong difference in metrological support in these cases is consistent with the practice of using the results obtained. Due to the specific nature of the typical problem setting and use of geophysical monitoring data, the inevitable and poorly controlled errors in these data are relatively less detrimental to the use of the data than would be the case in typical physical surveys. Geophysical monitoring tools often track the behavior of highly nonequilibrium systems, often with a subcritical behavioral pattern, which leads to great variability in their behavioral pattern. Examples of false, but at the same time statistically significant anomalies are given. The features of using statistical approaches in the analysis of nonequilibrium systems with a subcritical nature of behavior are discussed; in this case, some standard statistical approaches may be incorrect.

For remote monitoring of destructive processes during service of large industrial facilities, we have developed a low-cost approach for their reliable detection. It is based on low-amplitude seismic signal monitoring data. The source material comprises data from long-term real-time monitoring by highly sensitive instruments of seismic stations in the vicinity (up to 30 km) of the study object. In the technogenic component of seismic noise, low-amplitude signals are recorded as responses from mechanical oscillations (oscillation of operating equipment, natural oscillations of buildings and technical structures) of various objects. Such oscillations are characterized by certain frequencies and duration, making it possible isolate signals of some sources contained in seismic noise from others and increase the signal-to-noise ratio. The long-term monitoring results are used for retrospective data analysis and, on its basis, to determine anomalous changes in the frequencies and amplitudes of low-amplitude signals associated with destructive processes at the facility. This accounting increases the reliability of monitoring the stability of structures and operating equipment in real time, which is urgently needed to prevent breakdown and analyze the causes of emergency situations.

The practical results of earthquake detection with a distributed acoustic sensor (DAS) developed by PetroFibre LLC are reported. The operating principle of the DAS is based on interferometric detection of light resulting from Rayleigh scattering in optical fibers. The detected earthquake occurred in Iran. A fiber optic cable used as the sensitive element of the DAS was placed at the bottom of a shallow water region of the Black Sea, supervised by the Southern Branch of the Shirshov Institute of Oceanology, Russian Academy of Sciences. Gravity waves are shown to be a significant interference factor, preventing analysis of the wavefield for seismic event detection. Filtering the wavefield with a lower cutoff frequency exceeding 0.05 Hz was used to suppress the influence of the gravity waves. The specific features of the directivity pattern of the fiber optic cable as a sensitive element are considered; results are given indicating a lack of susceptibility of the cable to acoustic perturbations acting on it transversally.

The seismic coda wave attenuation characteristic in the area of the HPP cascade in the upper and middle reaches of the Vakhsh River was studied. The short-period coda waves of the local earthquakes, as recorded by frequency-selective seismic stations in 1958–1989, and digital seismogram data earthquakes that occurred in region since 1989 until 2021 were analyzed. A comparative analysis of seismological data obtained by analog and digital seismic stations has been carried out. The correlation of spatial inhomogeneities of the S-wave attenuation field with tectonics and seismicity in the area of the HPP cascade and in nearby territories is considered.

The aim of the study is to update the information content of the Automated Information Management System of the Russian Unified Emergency Prevention and Response in order to increase the reliability of seismic risk assessment results and ensure the safety of the population in earthquake-prone areas of the Russian Federation. The study area is Krasnodar krai, where according to review and detailed seismic zoning, possible source zones with М_max = 5.0, М_max = 5.5, М_max = 6, and М_max = 7 were identified. The relevance of this study follows from activation of seismicity in recent years in the considered area according to the detection by the network of the Geophysical Survey, Russian Academy of Sciences, of seismic events in a wide magnitude range with М ≥ 1, as well as a series of perceived earthquakes in May 2023 in the Tuapse region. The scientific novelty is that for the first time in the study of a single region, the results of all stages of the study are presented. Seismic hazard and seismic regime assessments are refined by analyzing moderate events with magnitudes of M = 3.3–4.5 from the beginning of the last century to the present, and the seismic risk indicators are computed at regional and urban levels. For the first time, we have performed a joint analysis of all obtained variables. Computer simulation was used to assess the risk parameters along with the Extremum GIS, developed with the participation of the authors. Maps of seismic risk social and economic indicators were compiled for the territory of Krasnodar krai, as well as for the city of Krasnodar, taking into account the updated data on the city building inventory.

Comparison of the spectral characteristics of ground vibrations from earthquakes with the level of seismic ambient noise in a wide range of periods makes it possible to assess the possibilities of seismic networks, taking into account the local conditions for the location of seismic stations. Based on the probabilistic approach, which allows one to estimate the statistical parameters of seismic variations in the frequency domain, a model of seismic ambient noise for the southeastern shore of Lake Baikal was developed. The study of the spectral characteristics of seismic waves was carried out on the basis of records of earthquakes in the Baikal rift zone with 3.5 ≤ M ≤ 6.9 that occurred during 2017–2022. The spectral characteristics of shear waves from earthquakes were calculated using bandpass filtering in nonoverlapping octave bands. Comparison of the calculated spectral characteristics of seismic vibrations from earthquakes with seismic ambient noise model made it possible to evaluate the possibilities of three broadband seismic stations. The approach can be used to select optimal equipment in terms of its characteristics, taking into account the local conditions for the location of stations.

The research develops the H/V method by designing a microseismic data processing workflow, which includes prefiltering, summation of amplitude spectra, calculation of the component spectrum ratio (H/V curve) and its inversion based on surface Rayleigh wave ellipticity curves. As a result of the algorithm, the resonance frequencies values, depth of the top of the bedrock, and S-wave velocity in the soil and bedrock are determined, tolerant to noise at the point of measurement. The search ranges of the solution to the inverse problem are evaluated using the results of processing active seismic data on refracted and surface waves. As a result of processing the H/V curves, distribution maps of the reconstructed parameters for the entire area of the vibroseismic test site near the settlement of Bystrovka, Novosibirsk oblast, are constructed. The depth of the top of the bedrock, calculated by different seismic methods, are highly correlated with each other. The distribution maps of the reconstructed parameters may apply for studying the near-surface section, estimating the depth of the top of the bedrock, determining the incremental seismic intensity by the seismic impedance method, or calculating synthetic earthquake accelerograms.