Fizika zemli
The journal «Physics of the Earth», founded in 1965, publishes the results of original theoretical and experimental studies in the fields of physics of the Earth's interior and applied geophysics. The journal publishes articles written by researchers of the Russian Academy of Sciences and scientific institutions of the Russian Federation. Articles by foreign authors are also accepted for publication.
Editor-in-Chief
Morozov Yu.A., corresponding member of the Russian Academy of Sciences.
Media registration certificate: № 0110188 от 04.02.1993
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No 3 (2025)
Articles
Magnetic Field Variations in Geodynamo Models
Abstract
An increase in the intensity of heat sources in the Earth’s core leads to a decrease in the intensity of the dipole magnetic field. The spatial spectrum of the magnetic field becomes multipole. The intensity of variations of the magnetic dipole and its deviations from the rotation axis increases. The dependence of the duration of magnetozones of constant polarity depends on the amplitude of the magnetic dipole according to a power law. The exponent of the power function can change by a factor of two depending on the dipole amplitude. Superchrons of the magnetic field correspond to high intensity of the magnetic dipole.
Fizika zemli. 2025;(3):3-8
3-8
On the Pseudo-Thellier Method for Single-Domain Non-Interacting Particles. Theory and Experiment
Abstract
The pseudo-Thellier method was numerically simulated based on a rigorous solution of kinetic equations for uniaxial, chaotically oriented, non-interacting single-domain particles. Laboratory experiments were performed to determine the relative paleointensity Bдр with thermoremanent magnetization (TRM) created on samples of igneous rocks in random fields Bсл. The domain structure of grains of these samples varies from single- to multi-domain. Both theoretical and experimental pseudo-Arai diagrams can be divided into two quasi-rectilinear sections, one of which is located in a relatively low-coercivity region Bc < 40–50 mT, and the second — at higher amplitudes of the alternating field (AF). Determinations of the relative paleointensity Bдр on igneous rocks bearing TRM, performed on low-coercivity segments of pseudo-Arai diagrams, give quite satisfactory results with a linear correlation coefficient R = 0.8 between the true field Bсл and Bдр, determined using the pseudo-Thellier method. It is shown that when taking into account thermal fluctuations for relatively magnetically soft and small particles (which corresponds to low blocking temperatures), there is a significant difference between the coercive force of a particle Bp and the actual field of its magnetization (demagnetization). The main conclusion of the work is that the application of the pseudo-Thellier method to igneous rocks is a promising direction, and its development in both methodological and practical aspects can bring interesting results, especially when applied to samples that are unstable to magnetomineralogical changes in the process of applying the classical Thellier method.
Fizika zemli. 2025;(3):9–22
9–22
Paleomagnetism of the Miocene Magnatic Rocks of the Southern Kamchatka
Abstract
Reconstruction of the tectonic evolution of Kamchatka is extremely important for understanding the formation mechanisms of folded belts and development of subduction systems. In this context, obtaining reliable paleomagnetic data from poorly studied segments of the Koryak-Kamchatka folded region, such as southern Kamchatka, is essential. This paper presents the first paleomagnetic data from the Miocene magmatic rock bodies of the Pribrezhny complex, which is widespread along the Pacific coast of southern Kamchatka. Based on 33 sites, the paleomagnetic pole for the Miocene of the southern Kamchatka was calculated, which is statistically significantly different from all published Cenozoic poles for nearby regions. The new data suggest that Miocene volcanic rocks formed at a paleolatitude close to their current position (52.3°), and indicate the origin of the Miocene supra-subduction volcanic belt on the more ancient base of the Olyutor-Kamchatka folded system, and not within a separate exotic block. It is shown that most of the sampled volcanics were formed before the main phase of tectonic deformations, but at least some of the studied bodies of normal polarity contain post-folding magnetization and may represent products of younger magmatic episodes.
Fizika zemli. 2025;(3):23–40
23–40
Archaeomagnetic Age of Ceramic Fragments from the Archaeological Multilayered Monument Ivanovskoe III
Abstract
Based on the archaeomagnetic study of four ceramic fragments from two cultural layers of the multilayered archaeological site Ivanovskoe III, the age of the ceramics is proposed based on the correlation with the VADM reference curve for the central part of the Russian Plain. For two ceramic fragments from the first cultural layer, the age of the Late Bronze Age that was determined typologically and by the radiocarbon method, is consistent with the age that was determined based on the correlation with the VADM summarized archaeomagnetic data. Radiocarbon dates for undecomposed wood found in the peat layer located under the second cultural layer have a wide range of values. Comparison with the graph of VADM dependence on age for the central part of the Russian Plain makes it possible to state that one of the ceramic fragments found in the second cultural layer is of Neolithic age. Low VADM values were obtained for the second ceramic fragment from the second cultural layer, which are not typical for either the Late Bronze Age or the advanced Neolithic. A distinctive feature of samples with low VADM determinations is that they contain thermally unstable maghemite. It is possible that the age of the second ceramic fragment corresponds to the Early Neolithic as a result of mixing the layers due to the economic activity of people who repeatedly inhabited this area.
Fizika zemli. 2025;(3):41–53
41–53
Local-Regional Decomposition of the Telluric Tensor
Abstract
The article considers the possibilities of using the telluric tensor in magnetotellurics, determined from the linear relations of the electric field at the ordinary and base points. Particular attention is paid to the local-regional decomposition of the telluric tensor, allowing to separate the influence of near-surface inhomogeneities and the studied deep structures. Approaches that are widely used in the analysis of the impedance tensor are adapted by the authors for the analysis of the telluric tensor and tested on synthetic data calculated for a three-dimensional model with a deep conductive structure and an inhomogeneous near-surface layer. A phase tensor determined from the telluric tensor and free from near-surface effects is considered. It is shown that maps of invariant parameters and polar diagrams make it possible to estimate the dimensions of the medium, localize deep structures and estimate their extension.
Fizika zemli. 2025;(3):54–69
54–69
On Refining the Form and Tensor of Electrical Conductivity of Local Inhomogeneity
Abstract
Based on the solution of inverse coefficient problems of direct current geoelectrics in a linear formulation, the method for refining the shape and an algorithm for finding the components of the electrical conductivity tensor of a local inclusion located in a piecewise constant medium are presented. The solution to the inverse problem of direct electric current for a local three-dimensional object characterized by the electrical conductivity tensor is presented. The study was carried out to clarify the shape of an anomalous object of complex geometry. The algorithm for refining the shape of a local anisotropic inclusion is proposed. The analysis of issues related to the application of this procedure was carried out. The results of computational experiments are discussed.
Fizika zemli. 2025;(3):70–87
70–87
Influence of Benched Mountain Relief on the Results of Magnetotelluric Soundings
Abstract
The aim of the conducted research was to estimate the influence of the relief, specified as a system of steep benches, on the apparent resistivity curves and the parameters of geoelectric sections determined from these curves during magnetotelluric observations. It was solved using three-dimensional mathematical modeling of magnetotelluric fields by the finite-difference method using the Maxwellf program. The dependences of the curves and the results of their one-dimensional inversion on the block parameters of the two-dimensional and three-dimensional models were analyzed. Distortions that shifted the invariant apparent resistance curves calculated on the steps of the staircase from the MTS curves measured at the flat ground-air boundary were estimated. At the same time, the geoelectric parameters of the blocks located under the flat boundary are equal to those specified under the model with the relief. The problem of constructing geoelectric models under conditions of stepwise changes in terrain can be solved using three-dimensional mathematical modeling of apparent resistivity curves adjusted by normalizing coefficients that take into account the transition to a 3D model with a flat ground-air boundary. However, they depend on the period of variations. Due to this, it is more appropriate to evaluate the use of three-dimensional inversion programs that include terrain topography in the starting three-dimensional models. Before carrying out this procedure, it is necessary to know what displacements of the apparent resistivity curves may occur if the influence of terrain and deviations obtained during their inversion, as well as geoelectric parameters of sections from test models are not taken into account.
Fizika zemli. 2025;(3):88–100
88–100
Application of Configuration Mechanics Methods to the Problem of Stimulated Volume Formation
Abstract
The zone of activated natural fractures (stimulated volume) in the process of hydraulic fracturing in the continuum approximation is considered as a growing porous body saturated with fluid. Varying the state of the body containing the surface of a strong fracture in the reference and actual configurations and writing the energy conservation law in the form of the principle of possible displacements, conditions for jumps in physical quantities at the fracture front are obtained. A model problem in a one-dimensional formulation is considered, and an estimate of the critical discharge pressure that initiates the process of the stimulated volume formation is made.
Fizika zemli. 2025;(3):101–114
101–114
Recent Movements and Deformations of the Earth’s Crust in the Region of Avacha Volcano (Kamchatka Peninsula) from 2015 to 2023
Abstract
The results of studies of recent crustal movements and deformations according to GNSS observations in the area of Avacha volcano in 2015–2023 are presented. Studies of Avacha volcano are especially important because it is an active volcano closest to the administrative center of Kamchatka Krai. Interesting features of local geodynamics of the area were revealed. Horizontal and vertical displacements, dilatation and full shear deformations, as well as characteristics of the deficit of “internal” displacements were analyzed. In the southern part of the network there is an accumulation of compression deformation due to pressure from the subduction zone. In the vicinity of the volcano crater, tensile strain accumulates in the absence of significant uplift. The characteristics of the internal displacement deficit show the response of the GNSS network to the M6.5 earthquake (03.04.2023) All changes in the characteristics of crustal motions and deformations demonstrated about two-year cyclicity. In further observations it will be possible to evaluate the stability of this phenomenon. It is also noted the need to expand the network of GNSS observations to the northern slope and foot of Avacha volcano for more detailed geodetic monitoring of its condition.
Fizika zemli. 2025;(3):115–128
115–128
New Methods for Analyzing the Nature of Seismic Regime Non-Stationarity
Abstract
Three new methods in geophysics for analyzing the non-stationarity of data series are used to analyze earthquake catalogs of the Kuril-Kamchatka and Mid-Atlantic Ridge regions. The possibility of identifying the non-stationary component of the seismic regime and the nature of non-stationarity are discussed. The use of new methods confirmed a number of known (expected) patterns and indicated a number of non-trivial points. Among these, the following were identified: a tendency of increasing non-stationarity with increasing characteristic time, which may conform to the correspondence of seismic activity spectrum to the flicker noise; 2) a difference in the nature of the magnitude distribution, possibly corresponding to a decrease in b-values, for clustering main events; 3) detection of two tendencies in the seismicity regime over time — clustering at smaller relative distances and repulsion at larger ones; these tendencies may correspond to the epochs of seismic activity growth and subsequent attenuation, during the accumulation of tectonic stresses. The results indicate the prospects of using these new analysis methods in seismology, providing clarification of the non-stationary nature of the seismic process.
Fizika zemli. 2025;(3):129–142
129–142
Radial Anisotropy of the Upper Mantle Of Southeastern Asia
Abstract
Radial anisotropy of S-waves is observed as a difference between SV- and SH-wave velocities polarized in vertical and horizontal planes and obtained by inverting dispersion curves of Rayleigh and Love waves, respectively. Unlike isotropic models, the currently existing distributions of S-wave velocities that take radial anisotropy into account significantly contradict each other. One of the reasons for such discrepancies is that, as a rule, different data sets (paths) for Rayleigh and Love waves are used to calculate a radial anisotropy coefficient. This leads to the fact that the reconstructed velocity sections of SV- and SH-waves are smoothed over areas of different shapes and sizes. To eliminate this effect, an approach in which initial data contain only Rayleigh and Love wave dispersion curves along the same paths at the same periods is offered. Then, standard procedures of surface wave tomography and inversion of local surface wave velocities into S-wave velocity sections are implemented. Using such an approach, a distribution of radial anisotropy coefficient (α = (VSH − VSV) / Vav, where Vav = (VSH + VSV) / 2) in the upper mantle of southeastern Asia to the depth of 300 km within 70°–145° E and 20°–40° N is obtained. It has been shown that at the depths of 50–70 km, maxima of α-coefficient are confined to areas with reduced SV-wave velocities. In addition, at 50 km, the maxima of α values tend to areas with maximum rates of horizontal displacements according to GPS data (relative to stable Eurasia). It has been revealed that areas with reliably established negative anisotropy (α less than −1%), i.e. in which VSV > VSH are confined to the boundaries of lithospheric plates.
Fizika zemli. 2025;(3):143-158
143-158
Regional Seismogravitational Heterogeneities of the Upper Mantle of the West Siberian Plate (Quartz Profile)
Abstract
The structure of the lithospheric mantle and asthenosphere has been studied based on data from nuclear explosions along the Quartz profile that is part of the Altai-Sayan folded region and intersects in the south-east direction the Pre-Ural trough with the Urals and the West Siberian plate. A two-dimensional seismic model of the upper mantle has been constructed in a directly spherical approximation of the Earth’s shape using the ray tracing method of the propagation of refracted-diving and reflected longitudinal waves. Regional structural-velocity heterogeneities of the two-layer mantle lithosphere have been discovered, with a decreasing thickness toward the folded region with a correspondingly increasing thickness of the asthenosphere. Particular attention is paid to the localization of mantle heterogeneity, corresponding to the location of the Koltogorsk-Urengoy rift graben. The distribution of residual mantle Bouguer gravity anomalies (recalculated to the base of the earth’s crust) shows clear zoning corresponding to seismic heterogeneities with a weak dependence on the Moho depth.
Fizika zemli. 2025;(3):159-170
159-170
Stochastic Simulations and Ground Motion Prediction Equation for Peak Accelerations, Peak Velocities and Response Spectra for the Ural Region
Abstract
The characteristics of radiation and propagation of seismic waves in the Ural region were refined based on stochastic modeling of the records of local earthquakes; these characteristics correspond to transient characteristics from areas of stable continental seismicity to seismically active regions with crustal seismicity. Ground motion prediction equation (GMPE) has been constructed for the Ural region, describing the dependence of peak accelerations (PGA), peak velocities (PGV) and acceleration response spectrum amplitudes (SA) on rock on magnitude and distance. The GMPE is applicable in a wide range of magnitudes (Mw = 4–6.5) and distances (1–250 km) and can be applied to assess seismic hazard in the design and construction of earthquake-resistant structures in the Ural region. To account for the epistemic uncertainty of the estimates of seismic impacts in probabilistic seismic hazard analysis and construct a logic tree, five alternative modern GMPEs from other regions were selected: a global model for crustal seismicity, two models developed for the mountain regions of the Swiss and French Alps, two models for regions of stable continental seismicity – eastern North America and Great Britain. These models were tested using the array of synthetic ground motion parameters; the equation for the Swiss Alps turned out to be the closest to the developed GMPE for the Urals.
Fizika zemli. 2025;(3):171–191
171–191
New Broadband Seismic Stations in the Central Part of the East European Platform
Abstract
The paper presents information on the development of a broadband seismic station network in the central part of the East European platform. Three new seismic stations have been installed: Udomlya (UDO), Borok (BROK), and Vladimir (VLD). Their recording capabilities have been analyzed. It has been shown that the use of data from new stations makes it possible to successfully register and locate both teleseismic and local seismic events of various origins. The location and quality of data from the new stations will make it possible to characterize the structure of the earth’s crust and upper mantle of the Fennoscandia and Volga-Uralia megablocks near their collision zone in the future.
Fizika zemli. 2025;(3):192–206
192–206