Seismic Instruments最新文献

The paper is devoted to development of a portable vibrating unit and study of its applicability in generating seismic waves. The solution to developing a portable vibrating unit problem capable of generating a stable seismic signal in the target frequency range is very important. Existing solutions are cumbersome and cannot be widely applied in engineering seismic exploration. The paper describes in detail the design of the vibrator source, the stages of output laptop signals testing, the power amplifier, and haptic transducer control. Signals with different frequency sweeps were used during field acquisition. The recorded data were processed by multichannel analysis of surface waves. As a result of comparing the amplitude spectra and dispersion images of the surface wave, it was found that a hyperbolic (low-dwell) sweep signal generates a surface wave train in the entire frequency range (10–150 Hz), but does not produce high-frequency interference waves in cement concrete pavement as opposed to other sweep signals and sledgehammers. Based on the field data processing results, we reconstructed a one-dimensional shear-wave velocity model for soils and concluded on the success, practicability, and increased (compared to a sledgehammer) efficiency of using the developed vibrator source for acquisition and analysis of surface wave data for engineering seismology problems. The undoubted advantages of using a vibration source are controllability of the frequency content and its repeatability. The use of such vibroseis devices combined with stationary seismic recording systems is a promising direction for solving seismic monitoring problems.

The paper analyzes the results of ground-based and satellite repeat geodetic observations at a gas and oil field. The set of available geological, geophysical, and geodetic data has made it possible to conduct a comparative analysis with theoretical vertical and horizontal displacements at the field. Analytical calculations were done with the deformable reservoir model. The results of the comparative analysis and conclusions indicate both regular correspondence and inconsistent results between theory and observations.

The article presents a preparatory stage for solving the thermoelasticity problem for a halfspace with relief. The effect of the relief on diurnal and season variations of the temperature in the upper layer of the crust induced by temperature variations the in atmosphere is studied. The case of weak two-dimensional relief is discussed. In this paper, we say that relief is weak if: (1) the angle of inclination of a relief element to the horizon is small; (2) the thickness d of the heated layer is small compared to the radius of curvature of the line of the relief. For the diurnal mode, we have d ≈ 15 cm, for the seasonal mode, d ≈ 3 m. The heat equation with a boundary condition of the first kind is considered, and an approximate analytical solution is obtained. The results are compared with the numerical solution, which can be considered. The approximate formula gives a satisfactory result if: (1) the angle of inclination of a relief element to the horizon does not exceed 0.2 rad; (2) the curvature of the line of relief does not exceed 2.4 × 10^–2 m^–1 for the diurnal mode and 1.2 × 10^–3 m^–1 for the seasonal mode. In this case the relative discrepancy between the numerical and approximate analytical solutions is less then 4% if the depth ≤20d. Temperature variations at a depth of 20d are already almost completely absent: the amplitude does not exceed ~10^–9–10^–8°C. Therefore, the underlying layers do not significantly effect on displacements and tilts of relief elements located near the surface.

The paper presents the results from upgrading the satellite geodetic network of the geodynamic test area of the Nizhne-Kansky massif using bedrock pin geodetic centers in 2021–2022. A brief review is given of the historical experience of using bedrock pin centers in developing satellite geodetic networks at geodynamic test sites, in particular, in areas where underground research laboratories are located. Based on this experience, the design and technology of installing rock geodetic centers were developed and implemented. The design of bedrock pin centers makes it possible to minimize the centering error and ensure immobility of GNSS equipment throughout the entire measurement session. The results of expanding the geodetic network in connection with the start of construction of an underground research laboratory in Krasnoyarsk krai are presented. The form of finite elements of the modernized geodetic network is analyzed. It is shown that construction of new GNSS stations had a positive effect on the network geometry. As a result, the network has increased the number of close-to-equilateral triangles (finite elements), which will have a positive effect on the accuracy in calculating the deformations of the Earth’s surface when processing geodetic measurement results and when forecasting the long-term stability of the geological medium in the study area.

As part of studies on the search for earthquake precursors, the authors have conducted an experiment on long-term precision monitoring of variations in the resistivity of the Earth’s crust in a highly seismic region of Tajikistan. The primary data of this experiment can be considered a special type of VES profile, in which, instead of a linear coordinate, the sounding date changes from picket to picket. When processing precision monitoring data, it is necessary to solve the inverse VES problem with the highest possible accuracy. VES curve inversion programs commonly used in electric exploration do not allow this. The authors have previously developed a special method for regularizing the residual functional, which suppresses the effect of resistivity buildup, due to which the error in reconstructing the resistivity of rocks for profiles with a strong seasonal variation in resistivity is reduced by an order of magnitude. However, in some cases, the regularized algorithm strongly biases estimation of the amplitude of the seasonal resistivity variation in the lower layers of the section. In this paper, the operation of the proposed algorithm is tested in detail for nine model profiles simulating a real geoelectric section. The considered profiles differed in the characteristics of the seasonal variability of resistivity in the lower layers of the section (the phase and amplitude of seasonal effects varied). It is shown that resistivity buildup is effectively suppressed in all cases. For each model profile, the error in solving the inverse problem is estimated. The effect of a biased estimate of the amplitude of seasonal variation is studied. It is shown that in most cases, analysis of the solution makes it possible to reveal the presence of such distortions and qualitatively assess their character. It is also shown that for profile options supposedly closest to the experimental profile, the estimates have minimal bias. For all profiles, the ratio of the average and maximum errors in calculating the resistivity in different layers to the residual in the solution to the inverse problem was evaluated. This makes it possible to evaluate the actual error of the reconstructed resistivity values knowing only the fitting residual. The paper also studied the possible effect of increasing the accuracy in solving the inverse problem in the case of preliminary decomposition of the apparent resistivity curves into seasonal and flicker noise components. It is shown that for small fitting residuals, the results change insignificantly. According to the results obtained, the error in reconstructing the aperiodic (flicker noise) component of resistivity variations in the lower layers of the considered section can be decreased to 0.4%. The accuracy in reconstructing the seasonal component of resistivity variations depends on the amplitude and phase of seasonal effects in the model profile. For the considered profiles, the error varies from 1 to 2%.

A set of tectonophysical methods has been applied to reconstruct the neotectonic stresses of the southeastern Altai Mountains within the Chuya–Kurai depression and its framing structures. It is suggested that at the neotectonic stage, the tectonic structures of the Altai Mountains underwent a transformation of geodynamic conditions—a situation of sublatitudinal horizontal compression with predominant reverse-fault and transpressional movements along faults that existed up to the Neogene was replaced by horizontal shear conditions with a NNE and NE subhorizontal compression axis and WNW and NW extension axis. With such a stress field, the dominant NW-trending faults in this territory are mainly characterized by dextral strike-slip displacements, and NE-trending faults, by sinistral. Submeridionally trending faults that formed at the neotectonic stage show clear signs of extensional structures. A feature of the faults of the Chuya–Kurai depression according to these studies is a fairly small number of megafractures (indicators of shear displacements) in shear zones. This indicates dominant reverse-fault and transpressional movements over large disjunctive structures in the region in the Paleozoic and Mesozoic versus neotectonic shear movements. The results of the research are of practical importance in studying the regional seismicity.

The article presents a new method of classifying acoustic and microseismic emission (KLASI-k), which analyzes waveform parameters (the rise time amplitude RA, average frequency AF, and the waveform index WI). The method is based on k-means clustering, which makes it possible to separate subsets of events differing in scaled seismic energy (the ratio of emitted seismic energy to released seismic moment) and source duration. In classifying seismic events, there is the fundamental possibility of using the source parameters (seismic energy E_s, seismic moment M₀, and corner frequency f₀) as the features of the KLASI-k algorithm. Good correspondence is observed between the classified subsets of events in the transition from waveform parameters {RA, AF, WI} to source parameters {E_s, M₀, f₀}. The KLASI-k method was applied to the data on mining seismicity induced by two ripple-fired blasts in the Gubkin Mine of the KMAruda Mining Enterprise at the Korobkovskoe iron ore deposit. The analyzed catalogs include 77 microevents recorded after the blast on July 6, 2019 and 259 microevents after the blast on October 24, 2020. Applying the KLASI-k method has made it possible to separate two subsets in the seismic catalogs. The events in the first subset show a scaled seismic energy (E_s/M₀) higher than 10^–7 J/(N m), while those in the second subset, lower than 10^–7 J/(N m). The first type of events have a smaller source duration than those of the second type; the released seismic moment is the same.

An algorithm is described, proposed by the author for predicting the coordinates of sources, energy classes, and time of realization of expected strong earthquakes within given energy and spatiotemporal limits. It is based on the self-similarity of a seismic process in a wide energy range and includes the formation of a sampling of relatively strong earthquakes from a seismic catalog for a monitored area. In earthquake preparation zones, the nature of the epicentral distribution of weak earthquakes of representative classes that occurred during the last tenth of the seismic cycle is determined: feature vectors. They are reduced to a scale-invariant form and serve as “samples” for comparison with feature vectors of predicted (virtual) earthquakes determined from the catalog. If sufficient information is available, the parameters of the tensors of the average focal mechanisms for each preparation zone are added to the feature vectors, taking into account their weight coefficients. The prediction is assumed to be done by the least squares method (LSM), based on the criterion of best fit of all parameters for virtual earthquakes and the samples. The algorithm envisages testing by retroprediction and the creation of a computer program with machine learning for its implementation. During testing, the expected errors in the estimates of the predicted parameters are determined.

The article provides an overview of software products developed at the Kola Branch of the Geophysical Survey of the Russian Academy of Sciences. These software products are aimed at automating the detection, location, and analysis of seismic and infrasonic events both locally (monitoring mines) and regionally (monitoring seismic and infrasonic activity in regions). A software package is also considered for searching for fragments of spent launch vehicles using signals from shock waves generated during their return to the dense layers of the atmosphere. The created software products are implemented in organizations both in the Russian Federation and abroad. Some of the programs are certified.

In the FENICS experiments, performed in 2007, 2009, 2014, and 2019 under the guidance of A.A. Zhamaletdinov, unique deep electromagnetic sounding data were obtained using grounded sections of industrial overhead power lines (OHPL) at distances from 180 to 840 km from the center of the supply line to the measuring installation. At the 2014 and 2019 stages, the components of the electromagnetic field and current strength in the source were recorded with VMTU-10 (VEGA LLC, St. Petersburg) measuring equipment, which allowed synchronous processing of measurement data with GPS referencing. Unlike the previous stages, in 2019, L-403 (Murmansk–Nikel) was used as a source with a sublatitudinal direction, which differs in a number of parameters from L-401, previously used for these purposes. The paper describes the main features of the generation of ELF–ULF radiation for geophysical research using industrial power lines.