bluuebunny/crossref_metadata_2025 huggingface dataset:
Conditions of the Formation and Evolution of the Tjörnes Transform Zone on the Basis of Physical Modelling
Authors: Grokholsky A. L. , Bogoliubskii V. A. , Dubinin E. P.
Published: April 2024

The Tjörnes Transform Zone (TZ) is on the northern margin of Iceland, mostly in the shelf zone. It connects the Kolbeinsey spreading ridge and the Northern Rift Zone (RZ) of Iceland. The zone is complexly structured and comprises several heterochronous sections that evolved in various geodynamic conditions. The geodynamic conditions of the formation and evolution of the Tjörnes TZ were reconstructed by means of physical modelling. The models measured the thickness of the model lithosphere, displacement, and the overlapping between the spreading segments. Results of the modelling show that the Tjörnes TZ formed successively, in two stages. The first stage was the formation of the general configuration of the area of interaction of the extension centres of the Kolbeinsey Ridge and the Northern RZ of Iceland in the form of a small overlap of the spreading centres with a rotating block between them. At the second stage, one of the formed transtensional fault zones between the spreading centres became the feeder channel for a magma pulse of the Iceland Plume, which led to the formation of the Grímsey Oblique Rift (OR). Standing alone is the Húsavík-Flatey fault zone that might have formed under the influence of two at a time spreading segments, with the domination of the more magmatically active Northern Rift Zone.
Analytical Models of Time-Dependent Physical Fields of the Earth: Local Version
Authors: Stepanova I. E. , Shchepetilov A. V. , Mikhailov P. S.
Published: April 2024

A new method for analytical description of time-dependent signals of different nature based on local and regional versions of the method of linear integral representations in spaces of different dimensions is proposed. The inverse problem of finding the field sources is reduced to solving ill-conditioned systems of linear algebraic equations with an approximate right-hand side. The results of a mathematical experiment on finding elements of nonstationary gravity and magnetic fields of the Earth are presented.
Stress Relaxation in a Cellular Model of Elements with Nonlinear Interaction
Authors: Cherepantsev A. S.
Published: April 2024

A model of stress relaxation in a system of discrete elements is analyzed. The model suggests analyzing a small-time scale of the process when external supply of additional stresses in the system are negligibly small. The nonlinear interaction of elements is similar to the interaction of elements in the open dissipative OFC model. Toppling conditions are determined by the static fatigue effect. It is shown that at a high level of element coupling, the model is characterized by a power-law decay of the drop frequency in time, similar to that observed in aftershock sequences of earthquakes. This regularity slightly depends on the initial distribution of stresses in the system, its exponent is p = 0.85–10 for the element coupling parameter α = 0–0.25. The analysis of the value of the time delay c for the formation of a power-law drop frequency decay shows that this parameter correlates with the duration of large-amplitude drops at the initial step of the relaxation process. The value c is defined in this case by the parameter α. Calculations also shows that relaxation of the mean stress σ(t) in the system of elements follows the relation \(t \propto {{e}^{{ - \gamma \sigma }}}\) with a time delay corresponding to the value for the drop frequency dependence. At the same time, there is no delay in the time series of the mean stress decrease during the drop of an individual element \(d\sigma \). The dependence \(d\sigma \left( t \right)\) is defined by the relation \(t \propto {{e}^{{ - \beta \Delta \sigma }}}\) in the entire temporal interval of the relaxation process. The value β linearly decreases with the increase of element coupling α in the model.
On Short-Period Dynamics in the Earth’s Core According to Ground-Based Observations of Geomagnetic Jerks
Authors: Riabova S. A. , Shalimov S. L.
Published: April 2024

The use of a special technique for processing variations of the geomagnetic field at several mid-latitude observatories allowed us to identify a series of jerks over a 17-year period, from 2004 to 2020. To interpret the experimental results showing that jerks follow with a quasi period of 3‒4 years, a probable mechanism of the occurrence of rapid changes in the geomagnetic field caused by unstable processes in the Earth’s core is proposed.
Study of the Crustal Displacement Fields by Space Geodesy Method at the Primorie
Authors: Timofeev V. Yu. , Ardyukov D. G. , Timofeev A. V. , Valitov M. G.
Published: April 2024

This work presents the results of GPS observations (2003–2020) carried out in Primorsky Krai (aka the Primorie) and Khabarovsk Krai in southeastern Russia. The objectives of our study were to obtain displacement velocities, to test the relation of current velocities with seismicity, with the specific features of the geological structure of the Primorie, and to study the rheological parameters of the crust and asthenosphere at the continental margin. This paper analyzes the results of measurements made in the Primorie at the Central Sikhote-Alin fault. The study includes the effects of the Tohoku-Oki earthquake in Japan with magnitude M = 9, which occurred on March 11, 2011. The zone of coseismic and postseismic displacements extends to a distance of over 1,000 km from the epicenter. The postseismic attenuations of the multi-year horizontal and vertical displacements allow us to estimate the relaxation time for the elastic-viscous model. With attenuation times of 4 to 8 years, the following viscosity values were obtained for the lower layer according to the two-layer rheological model:   8 × 1018–3 × 1019 Pa s. Using the bending model of the Earth’s surface and the bottom of the Sea of Japan, we estimated the thickness (20–25 km) of the elastic upper part of the Earth's crust in the continent–ocean contact zone.
Properties of Red Sea Pillow-Basalt Titanomagnetite at Different Distances from the Crust
Authors: Tselebrovskiy A. N. , Maksimochkin V. I. , Tatarintsev A. A. , Alekhina Yu. A. , Grachev R. A.
Published: April 2024

The magnetic properties and mineralogy of titanomagnetite in the Red Sea pillow-basalt at different distances from the contact surface with water were studied. It was revealed that the composition of titanomagnetite in the pillow basalt changes from the crust deep into the pillow: the titanium content in titanomagnetite increases, while the magnesium and aluminum content decreases. Titanomagnetite in the surface layer of pillow basalt (0–2 cm) is single-phase oxidized, with a maximum oxidation degree of 0.13, and at more than 3 cm from the crust has stoichiometric composition. According to the increase in magnetic susceptibility from 0.2 up to 1.8 × 10–2 SI, saturation magnetization from 0.026 to 0.895 A m2/kg and residual saturation magnetization from 0.014 to 0.296 A m2/kg, decrease in coercivity (Hc from 90 to 15 mT, Hcr from 153 to 20 mT), as well as by observations of electron and magnetic force microscopy, it is shown that the concentration of titanomagnetite in basalt and the grain size from single-domain state to pseudo-single-domain state increase with distance from the crust. The magnetic hardness of titanomagnetite grains was found to correlate with the maximum cooling rate of basalt. The NRM of basalt varies non-monotonically with distance from the pillow surface: up to a depth of about 3 cm its growth caused by the growth of titanomagnetite concentration was revealed, then a decrease caused by a decrease in the magnetic hardness of the grains. In spite of a rather strong variation of the magnetic properties in the 0–7 cm layer of pillow basalt, the experiments by the Thellier-Coe method for all layers showed close values of the geomagnetic field paleointensity (62.5–66.0 μT) with a high value of quality coefficient q (11–45). No regularity in the value of paleointensity with distance from the cushion surface was detected.
On the Nature of Negative Values of Induced Polarization in the Transient Electromagnetic Process when Working with an Axial Electrical Installation on the Sea Shelf
Authors: Ageev V. V.
Published: April 2024

The paper describes the ideas about the sources of induced polarization fields generated by external forces of non-electrical origin. Layered polarizable media are considered, over which a change in the sign of induced polarization can be observed for an axial electrical installation. Numerical model experiments substantiate the conclusion that the induced polarization is caused by galvanic currents and is not related to the induction component in this case.
Modeling the Composition of the Earth’s Liquid Outer Core
Authors: Anisichkin V. F.
Published: April 2024

The paper suggests expressions, coherent with experimental data, for the calculation of the sound velocity and the temperature of a condensed medium under pressures in the Earth’s liquid outer core through parameters of the shock Hugoniot of the medium. Additives to the Earth’s liquid outer iron-nickel core were fitted so that the calculated pressure, density and sound wave velocity corresponded to geophysical values and the temperature did not exceed the admissible limits. It was established that the iron carbide Fe3C containing (4.0 ± 0.5) wt.% carbon with additives of FeS2 and SiC with a total content of Si and S up to 1.5 wt.% meets the required criteria as the main light additive in the upper layers of the Earth’s core. Less probable is the additive of carbon in the diamond phase up to 0.5 wt.%. In the Earth’s outer core, at the boundary with the solid inner core, among the possible light additives are the iron carbide Fe3C with (3.5 ± 0.4) wt.% carbon or diamond phase carbon of (4.0 ± 0.5) wt.%. Additives at the bottom of the Earth’s liquid outer core, containing significant amounts of Si, S, are hardly probable. The content of H in the Earth’s liquid outer core can be significant at the minimum possible core temperatures. The content of O is insignificant.
Modeling the Accumulation and Transition to the Relic State of Methane Hydrates in the Permafrost of Northwestern Siberia
Authors: Arzhanov M. M. , Malakhova V. V.
Published: April 2024

This paper presents the results of numerical modeling of the permafrost thermal regime and thermobaric conditions of methane hydrates in the north of Western Siberia over the past 70 thousand years. The area of hydrate formation was determined and the rate of accumulation of hydrates was estimated in connection with the migration of fluid from the underlying gas-saturated layers under the conditions of cover glaciation. The estimates obtained for the change in hydrate saturation as a result of fluid migration during the 10 thousand-year glaciation period, depending on the permeability of the soil, are from 6 to 40% in the upper 350 m. Based on quantitative characteristics of the equilibrium and metastable states of methane hydrates, the conditions for the preservation of relict methane hydrates in permafrost under the paleoclimatic scenario were determined, taking into account periods of ice cover and transgression. It is shown that due to the effect of self-preservation at temperatures below –4°C, it is possible to preserve relict methane hydrates in the upper 200 m of soil under non-equilibrium conditions. The effect of lowering the temperature while the hydrates dissociate prevents the complete decomposition of the deposit and leads to an increase in the thickness of the frozen soil.
Paleomagnetism and Cyclostratigraphy of the Permian-Triassic Boundary Interval of the Staroe Slukino Section, Vladimir Region
Authors: Fetisova A. M. , Veselovskiy R. V. , Sirotin K. A. , Golubev V. K. , Rud’ko D. V.
Published: April 2024

The paper presents the results of paleomagnetic, rock magnetic, and cyclostratigraphic studies of continental red beds that compose the Permian-Triassic boundary interval of the Staroe Slukino section in the Vladimir Region, Russia. Based on the directions of the characteristic components of the natural remanent magnetization of the studied rocks in the sampled stratum, the intervals of normal and reverse polarity related to the regional magnetozones r2RnP, r3RnP, and N3P-T were identified. Within the r3RnP zone, there is an interval of anomalous paleomagnetic directions, which has similar characteristics to those identified earlier in the coeval intervals of the Nedubrovo, Zhukov Ravine, and Okskiy Siyezd sections. Revising the biostratigraphy allows us to assume that the two zones of anomalous paleomagnetic directions in the composite magnetic polarity scale of the upper Permian of the Russian Platform are a reflection of the same epoch of an anomalous geomagnetic field configuration. It is estimated by the cyclostratigraphic method that the studied 16 m interval of the Staroe Slukino section took 900±20 thousand years to accumulate, which limits the duration of the geomagnetic field anomalous state near the Permian-Triassic boundary to ~110 000 years. A new Permian-Triassic (~252 Ma) paleomagnetic pole of the East European Platform is calculated: plat = 36.3°; plong = = 155.0°; dp/dm = 2.8°/4.8°.
Results of Seismological Monitoring in the Baltic Sea and Western Part of the Kaliningrad Oblast Using Bottom Seismographs
Authors: Kovachev S. A. , Krylov A. A.
Published: April 2024

In 2007–2015, Shirshov Institute of Oceanology of the Russian Academy of Sciences (IO RAS) carried out seismological observations in the water area and on the coast of the Baltic Sea using autonomous seismic stations. Here, in the area of the Sambia Peninsula, previously considered aseismic, a strong perceptible earthquake with a magnitude of about M = 4.6 occurred in 2004. The most interesting data were obtained by IO RAS in 2008–2009 from seismological monitoring using autonomous bottom and coastal seismic stations. The data obtained in 2010–2015 turned out to be unsuitable for full-scope processing due to several causes (losses of bottom seismographs, high noise level at coastal stations, etc.). Seismological monitoring in the west of the Kaliningrad region and in the adjoining area of the Baltic Sea detected weak earthquakes with magnitudes ML = 2.5-3 whose sources are confined to the development are of the Kravtsovskoe offshore oil field. Some of these earthquakes have been recorded by the stations of the Norwegian seismic array NORSAR and by the seismic stations of Sweden. The Kravtsovskoe oil field is located on the shelf northwest of the unique natural object, the Curonian Spit. The detected weak earthquakes are likely to be anthropogenic, induced by reservoir pressure disturbances as a result of intensive hydrocarbon production, and are probably precursors of a strong man-made earthquake.
Lithosphere Density Model of the Middle Urals Segment
Authors: Ladovskii I. V. , Martyshko P. S. , Tsidaev A. G. , Kolmogorova V. V. , Byzov D. D.
Published: April 2024

For the Middle and North Urals segments and adjacent territories of the East European Platform and West Siberian Plate (within the graticular trapezoid with geographic coordinates 53–65° N, 48–72° E), ten deep seismic sounding (DSS) profiles were reprocessed using two-dimensional (2D) seismic tomography method, and gradient sections of crustal velocities were constructed in the form of grid functions. In the same format, density sections were constructed. The coefficients of density–velocity empirical correlation were calculated using the solution algorithm of 2D inverse problem of gravimetry. The method and calculation technology of a three-dimensional (3D) density distribution with tying to 2D data from reference seismic sections are embedded in the procedure of quantitative interpretation of potential fields with construction of 3D geophysical models. A stable solution of the 3D inverse problem of gravimetry is sought on the correctness set of the family of horizontal layers with 2D density distribution.
Latitudinal Variations of the Geomagnetic Field
Authors: Reshetnyak M. Yu.
Published: April 2024

The model of variations in the Earth’s magnetic field with random Gaussian coefficients is considered. It is shown that at small amplitudes of random nondipole field component σ, the scatter of the direction of the virtual geomagnetic pole grows with increasing latitude. At large σ, the scatter does not change much and its maximum is located at middle latitudes.
Kinematic Dynamo Modeling and Its Peculiarities in Polar Latitudes
Authors: Shatalov N. A. , Chechetkin V. M. , Shalimov S. L.
Published: April 2024

The results of calculations of the magnetic field structure in the kinematic approximation are presented, testifying to the consistency of the constructed numerical model with the structure of the flows of a conducting liquid: the instability of the convective process in a rotating spherical shell is reflected in the evolution of the magnetic field, manifesting itself in the pulsation regime of the field. It is shown that the features of the field evolution in the calculations are most clearly pronounced at high latitudes and have analogs in the behavior of the real geomagnetic field.
Micromagnetic Calculations of the Domain Structure of Submicron- and Micron-Sized Magnetite Grains
Authors: Shcherbakov V. P. , Sycheva N. K.
Published: April 2024

The evolution of the domain structure (DS) of cubic submicron- and micron-sized magnetite particles has been studied in detail during “cooling” of specimens from the Curie temperature Тс to room temperature Тr followed by their “reheating” to Тс in order to determine the degree of irreversibility of DS changes during heat treatment and their possible effects on the thermoremanent magnetization (TRM) properties. It is shown that typical magnetic configurations in particles up to 2 μm in size have flower or vortex shapes with one or two vortices. A model of the formation of thermoremanent magnetization (TRM) in submicron-sized pseudo-single-domain particles (PSD) is proposed based on an expansion of Neel’s single-domain thermofluctuation model of TRM acquisition. According to the model, the equality of blocking and deblocking temperatures is retained for submicron PSD grains. Consequently, for this magnetic fraction, the Thellier laws of pTRM additivity and independence must also be valid.
Remote Sensing of the Electromagnetic Effects of the Tonga Volcano Eruption on January 15, 2022
Authors: Gavrilov B. G. , Poklad Yu. V. , Ryakhovsky I. A. , Ermak V. M.
Published: April 2024

The possibility of remote studies of electromagnetic and ionospheric effects caused by the eruption of the Tonga volcano on January 15, 2022 is shown. At distances up to 15 000 km from the source, geomagnetic field variations associated with disturbances of the Schuman resonance (SR), Lamb wave propagation and acoustic-gravitational waves are registered. It is shown that the appearance of a powerful source of thunderstorm activity caused by the eruption produced a significant increase (more than three times) in the amplitude of geomagnetic disturbances at SR frequencies, which correlates with the number of lightning discharges. The effect of the eruption on the frequency characteristics of the SR was not detected.
Seismohydrogeological Phenomena as an Earthquakes’ Trigger Impact on Groundwater (by the Example of the Wells of the Petropavlovsk-Kamchatsky Test Site, Kamchatka Peninsula)
Authors: Kopylova G. N. , Boldina S. V.
Published: April 2024

Based on the long-term observations of the wells on the Petropavlovsk-Kamchatsky Test Site, the Kamchatka Peninsula, the paper analyzes manifestations of three main types of seismohydrogeological effects – hydrogeological precursors, coseismic pressure jumps and postseismic effects of the vibrational impact of seismic waves in measurements of the pressure and chemical composition of groundwater, depending on the earthquake parameters (magnitude, epicentre distance, intensity of seismic impact in the observation areas). The paper presents data on the earthquakes that were preceded by hydrogeological precursors in several (n = 2–4) wells. It is discussed whether it is possible to use hydrogeological precursors to predict strong earthquakes in Kamchatka. The authors also discuss the results of their experimental use in a real-time environment with weekly reports on the current observational data for the Kamchatka Branch of the Russian Expert Council. By the example of water level observations in YUZ-5 Well, the authors analyzed coseismic jumps in the groundwater pressure due to rupture formation in the sources of local Mw 6.0 earthquakes and four types of effects of the vibrational impact of seismic waves during local and distant Mw = 6.8–9.3 earthquakes at epicentral distances from 80 to 14 600 km; the study demonstrates that such effects depend on the earthquake parameters and the intensity of seismic impact in the well area.
Possible Seismogenic-Trigger Mechanism of Methane Emission, Glacier Destruction and Climate Warming in the Arctic and Antarctic
Authors: Lobkovsky L. I. , Baranov A. A. , Ramazanov M. M. , Vladimirova I. S. , Gabsatarov Y. V. , Alekseev D. A.
Published: April 2024

Abstract-A seismogenic-trigger mechanism is proposed for the activation of methane emission on the Arctic shelf in the late 1970s, which caused the onset of a rapid climate warming in the Arctic, as well as the intensive destruction of the ice shelves of West Antarctica in the late 20th and early 21st centuries. This process is accompanied by the release of methane from the underlying hydrate-bearing sedimentary rocks and the rapid climate warming in Antarctica. The proposed mechanism is associated with the action of deformation tectonic waves in the lithosphere-asthenosphere system, caused by strong earthquakes occurring in the subduction zones closest to the polar regions: the Aleutian, located in the northern part of the Pacific Ocean, and the Chilean and Kermadec-Macquarie, located in the southeastern and southwestern parts of the Pacific lithosphere. Disturbances of the lithosphere are transmitted at an average speed of about 100 km/year over long distances of the order of 2000–4000 km, and the associated additional stresses that come to the Arctic and Antarctica several decades after earthquakes lead to the destruction of metastable gas hydrates located in the frozen rocks of the Arctic shelf or in the subglacial sedimentary rocks of Antarctica, causing the greenhouse effect of warming. Moreover, transmission of additional stresses causes a decrease in the adhesion of sheet glaciers to the underlying rocks, their accelerated sliding and the destruction of the ice sheet ice shelves in Antarctica. The considered hypothesis leads to the conclusion that in the coming decades, the processes of glacier destruction and climate warming in Antarctica will increase due to an unprecedented increase in the number of strongest earthquakes in the subduction zones of the South Pacific Ocean in the late 20th and early 21st centuries.
On the Mechanisms of Generation of Excessive Horizontal Compression in the Continental Crust
Authors: Rebetsky Yu. L.
Published: April 2024

It is proposed to consider the processes of surface denudation and crustal magmatism to explain the formation of increased horizontal compressive stresses in the crust, which are excessive relative to the lithostatic pressure. Exhumation of a rock results in only partial unloading of the crust due to the removal of the weight of the overburden, unless the crust is above the yield point. This is due to the fact that in the case of exhumation, the unloading follows the elastic law. As a result, residual stresses of horizontal compression received at the stage of cataclastic flow arise in the rock. Another mechanism of formation of additional compressive stresses in the crust is related to volcanic and magmatic processes. The ascent of a magma along subvertical faults and fracture networks is only possible under the conditions when the magma pressure at the propagation front exceeds the level of horizontal compression in the rock. As a result, below the magma propagation front, the level of horizontal compressive stresses in the rocks rises to the level of magma pressure. Since the pressure in the subcrustal or intracrustal magma chamber is close to the lithostatic pressure of the overburden, above the magma propagation front in the fault, the stresses normal to the fault exceed the level of vertical compression. Thus, crustal magmatization is capable of changing the crustal stress state from horizontal extension to horizontal compression.
Numerical Simulation of Material Ejection into the Atmosphere Induced by Oblique Impacts of Ten-Kilometer-Diameter Asteroids into the Ocean
Authors: Shuvalov V. V.
Published: April 2024

The results of a three-dimensional numerical simulation of the oblique impacts of ten-kilometer asteroids at an angle of 45° onto a solid surface and into an ocean with a depth of 1 to 6 km are presented. The maximum masses of water, impactor, and soil ejected into the atmosphere and the masses of water, impactor material, and soil remaining in the atmosphere 10 minutes after the impact are calculated. The mass of vaporized ejecta is determined. It is shown that there are 2–5 times more impactor material and soil ejected into the atmosphere during oblique impacts than during vertical impacts.
Concurrent Active Acoustic and Deformation Monitoring of Hydraulic Fracture in Laboratory Experiments
Authors: Zenchenko E. V. , Zenchenko P. E. , Nachev V. A. , Turuntayev S. B. , Chumakov T. K.
Published: April 2024

The results of laboratory experiments on concurrent active acoustic and deformation monitoring of a hydraulic fracture are presented. The experiments were carried out in a model material based on gypsum. For comparison, reference experiments were carried out to study ultrasonic waves propagation through a liquid-filled gap of controlled width between two precision glass plates. The purpose of the experiments was to study the dependence of the amplitude of the ultrasonic wave passing through the crack on the magnitude of its opening. In these experiments, a circular hydraulic fracture was created, the plane of which was perpendicular to the axis of the cylindrical sample. A cased injection well was located along the same axis, ending at the middle of its height. The sample was placed between two aluminum alloy disks equipped with piezoceramic transducers built into them, operating both in the emitter and receiver modes. Through the channel in the lower disk, the working fluid was supplied to the fracture. The sample was saturated with pore fluid through the upper disk. The entire assembly was placed in a hydraulic press providing a constant compressive force. The crack opening value varied depending on the flow rate of the fluid supplied to the center of the crack and was measured by the relative change in the distance between the disks of the assembly using inductive displacement transducers. Experiments were also carried out simulating a fracture filled with proppant. In this case, the crack aperture varied depending on the applied vertical force on the sample. Based on the results of experiments carried out under various conditions, the dependences of the amplitude of the ultrasonic wave that passed through the crack were plotted. It has been experimentally established that sound attenuation in the hydraulic fracture, which has a natural roughness, is two times lower than in the gap between precision glass plates. The obtained results will make it possible to estimate the value of hydraulic fracture opening in laboratory experiments conducted on larger samples using active acoustic monitoring.
Geoelectric Model of the Central Part of the Northern Caucasus and Its Fluid Saturation
Authors: Belyavsky V. V.
Published: April 2024

A series of magnetotelluric and seismic studies have been carried out on profiles covering more than two thousand kilometers within the North Caucasus region. The earlier interpretation of the magnetotelluric observations by means of one– and two–dimensional inversion and three–dimensional mathematical modeling software has helped to construct a series of sections and models which are viewed as test and starting ones for the construction of a three–dimensional geoelectric model of the region. The test models have been used to test how well the software for three–dimensional inversion of the impedance tensor components in the magnetotelluric sounding method can estimate the parameters of conducting blocks in the structures of the Greater Caucasus and the Scythian plate. In the resulting geoelectric model, constructed from the results of three–dimensional inversion of all impedance tensor components, the position of low–resistance blocks correlates with deep faults, volcanoes of various genesis, and seismically active zones characterized by the reduced velocity of seismic waves and their increased absorption. The electrical resistivity of low–resistance anomalies is explained by the degree of their saturation with the fluid water fraction. Its maximum concentration is found within the intersections of fault systems, flexural–rupture zones, and deep faults activated by tectonic processes.
Dissipative Seismicity for Hydrocarbon Reservoir Parameter Evaluation
Authors: Chebotareva I. Ya. , Rode E. D.
Published: April 2024

The natural seismic background of the Earth and its deep emission component are a form of dissipation of energy of geodynamic processes. The methods of studying the seismic background as a signal generated by an open complex non-linear system (the Earth’s crust) can be grouped under one branch—dissipative seismicity. In this paper, one of such methods, namely, the thermodynamic indicator of the state of rocks, is used for the remote evaluation of the local productivity of the reservoir on the hydrocarbon deposit site. The thermodynamic indicator was created using the Klimontovich entropy and yields quantitative estimates of the local disequilibrium of rocks associated with the activity of geophysical processes. We revealed monotonic, near-linear relationship between the thermodynamic indicator values calculated using the seismic background records and the cumulative thickness of productive layers in the wells in close proximity to recording points. The thermodynamic indicator is calculated assuming that there is a sliding time window threshold that must be taken empirically. The obtained results show that the thermodynamic indicator can be effectively used for outlining the deposit boundaries and choosing the potentially most productive well drilling points by extrema in the indicator value field.
Thermal History of the Lithosphere of the Koltogor-Urengoi Graben, West Siberian Basin, in the Vicinity of the SG-6 Well: Numerical Reconstruction Using GALO Flat Basin Modeling System
Authors: Galushkin Yu. I.
Published: April 2024

The GALO basin modeling system is used to numerically reconstruct the thermal regime of the West Siberian basin lithosphere in the Koltogor-Urengoi graben in the vicinity of the Tyumenskaya SG-6 superdeep well. The reconstruction explains the features in the formation of the thermal regime of the basin, which were not considered in the previous reconstructions of the region. These features include anomalously high growth of the maturity level of the organics in the Jurassic and Triassic rocks, high temperature gradients observed in the upper basement and Triassic–Permian sedimentary complex, the anomalously low rock temperatures in the upper layers of the recent sedimentary section of the basin. The temporal changes in the tectonic subsidence of the basin are analyzed to estimate the intensity and duration of thermal activation events and the extension of its lithosphere. The thermal impact of the sill that intruded into the upper basement horizons in the Lower Jurassic explains the high degree of maturation of the organic matter in the Lower Triassic rocks. Taking into account the abrupt climatic fluctuations in the Pliocene–Quaternary together with hydrothermal activity in the bottom part of the sedimentary cover in the Upper Pliocene–Lower Pleistocene, we obtained the depth profiles of temperatures and vitrinite reflectance, which agree well with the measured values.
Changes in Thermal Conductivity of the Rocks of the West Siberian Basin Lithosphere in the Vicinity of the Tumenskaya SG-6 Well
Authors: Galushkin Yu. I.
Published: April 2024

Numerical reconstructions of the thermal regime of the lithosphere of the West Siberian basin in the Koltogor-Urengoi graben in the vicinity of the Tyumenskaya SG-6 superdeep well are used to analyze the depth distribution of thermal conductivity of basin rocks. Five depth intervals which differ in the character of changes in thermal conductivity of rocks are distinguished: the permafrost zone, the sedimentary section below this zone, the zone of anomalous rock weakening, the consolidated crust, and the mantle. The algorithms for calculating the thermal conductivity are considered and the main factors affecting its change with depth are determined for each of the five intervals. A sharp decrease in the thermal conductivity of rocks in the bottom part of the sedimentary cover and in the basement top in the vicinity of the SG-6 well is associated with rock weakening due to tectonic fracturing and hydrothermal erosion. The analysis suggests that the stationarity conditions of the process are not observed in optical scanning thermal conductivity measurements and, therefore, this method may overestimate the true thermal conductivity of rocks.
Mapping of Magmatic Complexes Based on Hydromagnetic Surveys in the Barents Sea Region
Authors: Lygin I. V. , Arutyunyan D. A. , Sokolova T. B. , Kuznetsov K. M. , Krivosheya K. V.
Published: April 2024

We have investigated nearly all of the currently available hydromagnetic survey data to study the magmatic structures in the sedimentary basin of the Barents Sea region. We use the modern interpretation techniques to process over 93 000 kilometres profile data of 1995–2017s. It was established that north-west striking dyke groups are abundant in the central and northern parts of the basin; in the south part no dykes were found. Magmatic structures in the sedimentary basin are reflected by the local magnetic anomalies of two types – the linear ones sourced by dykes, and mosaic ones associated with the local areas of magmatism. At sea depth of 100–500 m and sediment thickness over 8 km, the dominant depth of the upper edges of the bodies generating anomalies is about 1500 m.The analysis of the magnetic anomalies could help us to outline more exactly the sedimentary structures, the history of the magmatic processes and the tectonic evolution of the Barents Sea Region.
Spreading in the Northern Part of the Eurasian Lithospheric Plate from GPS Measurements and Its Possible Geodynamic Interpretation
Authors: Shevchenko V. I. , Lukk A. A.
Published: April 2024

Over the whole area of the Eurasian lithospheric plate considered in the paper —rom the Atlantic to the Pacific Ocean—the velocity vectors of the horizontal eastward displacements of GPS sites form a gentle, smooth, huge arc, convex towards the north. Three relatively narrow bow-shaped bands can be distinguished within the arc. The southernmost band, most provided with measurement data (bow-shaped band A in this paper) is discussed in detail in (Shevchenko et al., 2021). The direct, real results of the published geodetic measurements have shown that the length of this band increases by 5 to 10 mm annually. The arc is lengthening. In the cited paper, we considered and rejected five interpretations of this lengthening, which are based on the idea of external action of the above bow-shaped band on the rocks of the Earth’s crust/lithosphere. The most probable cause of the elongation seems to be the internal process of the increase in the volume of these rocks within the band due to the supply of the additional mineral material into these rocks by the deep fluids and its subsequent crystallization. In this paper, we present the results of similar geodetic measurements in other two bow-shaped bands, B and C. It turns out that bow-shaped band C located to the north of the other bands, is lengthening (and at a similar rate) as band A located to the south of the other bands. At the same time, bow-shaped band B, which has an intermediate position between bands A and C, is moving eastward without lengthening. Geodetic measurements in the axial part of the Mid-Atlantic Ridge in the Iceland island suggest that the general expansion of the Atlantic Ocean and the corresponding eastward motion of the Eurasian lithospheric plate are related to the injection of plastic magmatic wedges (of basic composition) in the axial, rift zone of the ridge. Against the background of this general eastward motiont of the lithospheric plate, its constituent parts (the bow-shaped bands A and C are markers of these parts) are moving in the same eastward direction with a velocity increasing from west to east. We attribute this increase in the velocity and the corresponding lengthening of the two bands to the above inflow of the additional mineral material and its subsequent crystallization.
Analysis of Contemporary Deformations of the North-Western Caucasu s and Ciscaucasia Based on GNSS Data
Authors: Steblov G. M. , Agibalov A. O. , Beloborodov D. E. , Zaitsev V. A. , Perederin V. P. , Perederin F. V. , Sentsov A. A. , Fadeeva K. V.
Published: April 2024

The field of the contemporary deformation of the North-Western Caucasus and Ciscaucasia is described based on GNSS horizontal movement data. It is shown that the deformation velocity is sufficient for the activation of large-scale faults of the region to be followed by seismic events with a moment magnitude of up to 7.0. Yet, the orogenic uplift at a rate of up to 12 mm/yr and the development of its varied, deep-broken relief cannot be explained only by the effect of external horizontal stresses. These processes are conditioned, to a great extent, on internal isostatic forces.
Corrections to the Theory of Elastic Bending of Thin Plates for 2D Models in the Reissner Approximation
Authors: Trubitsyn A. P. , Trubitsyn V. P.
Published: April 2024

Elastic bending stresses and strains in the lithosphere are typically calculated based on the Kirchhoff–Love (thin) plate theory. The criterion for its applicability is the smallness of plate thickness to length ratio. In oceanic plates, due to the buoyant force of the mantle, the main deformations are not uniformly distributed along the plate but are concentrated in the vicinity of the subduction zone. Therefore, the effective length of the bending part of the plate is a few fractions of the actual length, and the criterion of a thin plate is partially violated. In this paper, we analyze the possibility of applying thick plate bending equations. The existing variational theories of 3D bending of thick plates are much more complicated than the Kirchhoff–Love theory, as they involve solving three differential equations instead of one, and have limited application due to their complexity. Since geophysical applications frequently use 2D models, in this paper we analyze in detail the potential and accuracy of the thick plate bending theory for 2D models. After the conversion to the 2D plane strain and plane stress approximation, the original 3D Reissner thick plate bending equations are written out in the form similar to the Kirchhoff equations with additive corrections and are supplemented with the explicit formulas for longitudinal displacement. The comparison of the analytical solutions of the 2D Reissner equations with the exact solutions shows that the 2D approximation only provides a correction for the plate bending function. However, this correction refines the Kirchhoff–Love theory by almost an order of magnitude. At the same time, the solution of the equations in this case turns out to be almost as simple as the solution of the thin plate equations.
Magnetic Effects of the Double Earthquake of March 16, 2022 (Japan). Observation Results
Authors: Adushkin V. V. , Spivak A. A. , Loktev D. N. , Rybnov Yu. S. , Tikhonova A. V.
Published: April 2024

Abstract—The magnetic effects of strong earthquakes are considered using the example of a unique event: two underwater earthquakes of magnitude 6.0 and 7.3 that occurred on March 16, 2022 at close times (at 14:34 and 14:36 UTC, respectively) with a distance between sources of ~11 km. With the use of data from the Mikhnevo geophysical observatory of the IDG RAS (MHV) and a number of magnetic observatories of the INTERMAGNET international network, it is shown that in the absence of global geomagnetic disturbances, earthquakes were accompanied by characteristic variations of the Earth’s magnetic field recorded as a train of alternating geomagnetic field oscillations with an amplitude of ~2–8 nT and a period of ~30 min almost simultaneously at ~15:30 UTC by all magnetic observatories located at distances from 210 to ~13 000 km, as well as by variations in the periods of passage of the seismic and infrasonic signal in the MHV.
The Khubsugul Earthquake of January 12, 2021, ML = 6.9, in the Seismicity Structure of the Tuva-Mongolian Block
Authors: Emanov A. F. , Emanov A. A. , Chechel’nitskii V. V. , Shevkunova E. V. , Fateev A. V. , Kobeleva E. A. , Arapov V. V. , Frolov M. V.
Published: April 2024

Abstract—The paper presents the studies of the Khuvsgul earthquake on January 11, 2021 at 21:32 UTC (January 12, 2021 at 05:32 local time), MW = 6.7, ML = 6.9, and the seismicity structure in the aftershock period for the Altai-Sayan mountain region and the Baikal rift zone, where the epicenter of this earthquake was located. Two faults are seismically activated, diverging from the southern end of the aftershock area at an acute angle: one in the northeast and one in the northwest direction, as well as transverse faults between them. According to the epicenter position and studies of the source area by other authors, the main event corresponds to the northeastern fault, and large aftershocks occurred at the junction of the northwestern fault with transverse faults feathering from the east. The main event was immediately followed by a series of large aftershocks, the strongest of which occurred on March 31, 2021 with ML = 6.2 and on May 3, 2021 with ML = 6.4. Spatial changes in the seismic regime of the aftershock region led to the predominant activity of its southern end. The junction area of the collisional structures of the Altai-Sayan folded zone and the rift structures of the Baikal depressions system is distinguished in seismicity as a block structure with increased seismicity near the block boundaries. First of all, these are the Tuva-Mongolian block and the eastern part of the Sayano-Tuva block. After the Khuvsgul earthquake of 2021, a block structure with the activation of the epicentral zones of the 1991 Busingol earthquake, the 2011–2012 Tuva earthquakes, and other structures seismically active until 2021 has increased seismic activity. It is proved that the 2014 Khubsgul earthquake occurred under the basin of the same name and is associated with other faults than the 2021 earthquake and is not a direct precursor of the 2021–2022 activation.
On an Analytical Representation of an Integral Related to the Fock Integral That Appears in Calculations of the Electromagnetic Fields of Dipole Sources at the Interface between Two Half-Spaces
Authors: Kevorkyants S. S.
Published: April 2024

Abstract—The Fock integral is called after Fock who introduced it for the theoretical analysis of the electromagnetic field of magnetic dipoles at the boundary of a uniform conducting (nonmagnetic) half-space and obtained its analytical expression in terms of cylindrical functions. Detailed analytical representations of integrals, where all components of the fields of the vertical and horizontal magnetic dipoles are expressed, are reported in [A.V. Veshev et al., 1971]. To obtain analytical expressions for similar integrals representing the components of the fields of electric dipoles in a similar model, it is necessary to consider not only the Fock integral but also another related integral conditionally called the Fock integral 1 whose analytical expression is still unknown. The aims of this work are to derive an inhomogeneous linear first-order differential equation for this integral with the corresponding boundary conditions and to obtain the analytical representation of the Fock integral 1 by solving this equation. The result of this work will allow one to simplify the simulation of fields in a uniform half-space and to improve the interpretation of electromagnetic data due to more accurate and reliable estimates of the normal field in such models of a host medium.
Reconstructions of Paleowind Directions in the Pleistocene: Evidence from the Anisotropy of Magnetic Susceptibility of the Loess–Paleosol Series of Tajikistan and the Azov Region
Authors: Meshcheryakova O. A. , Kurbanov R. N. , Pavlov V. E.
Published: April 2024

Abstract—The magnetic fabric of the reference Khonako-II (south Tajikistan), Beglitsa, and Chumbur-Kosa (Azov region) loess-paleosol sections was studied to reconstruct the paleowind directions during the Middle and Upper Pleistocene. The paleosols and loesses of the Khonako-II section represent a promising object for study of paleowinds. Our data indicate a prevailing ~ northwestward or ~northeastward wind directions during accumulation of the upper 40.8 m of the section. Thereby, a change from warm (pedocomplex 2) to cold (loess 2) epochs during the accumulation of the lower half of the studied sequence (end of the Middle Pleistocene) was accompanied by “switching” the predominant winds (from northwestern to northeastern ones), whereas accumulation of the upper part of the sequence was mainly controlled by winds of intermediate directions. The latter can be considered as evidence for the lesser contrast of wind rose during later epochs that were responsible for the formation of the upper part of the sequence. The study revealed that the magnetic fabric of loess and paleosol horizons of the Azov region sequences was deformed and cannot be used for paleowind reconstruction. It was demonstrated that sampling using plastic container technique widely applied in studying loess–paleosol deposits could led to the significant deformation of primary magnetic fabric.
Geoelectric Interpretation of the Magnetic Monitoring Data in the Southwest Part of Baikal
Authors: Orekhova D. A. , Popova I. V. , Korotaev S. M. , Kruglyakov M. S. , Budnev N. M. , Kiriakov V. Kh. , Moskalev I. S.
Published: April 2024

Abstract—The long-term gradient magnetic measurements performed in the southwest part of Baikal as supplementing the experiment on deep-water monitoring of the electric field vertical component, can be applied to study the deep geoelectric section. Baikal cannot be approximated by a two-dimensional model in the region under study. Therefore, a three-dimensional geoelectric model of the lake and adjacent territories was constructed based on the existing geological and geophysical data. However, these data are insufficient for the region where our observations are carried out. Refinement of the section upper part over the magnetic field gradients on long bases has been performed using the neural network inversion method. Then, proceeding from the obtained basic model, alternative models were developed, which reflect the known hypotheses about the structure of the deep part of the Baikal rift section: mantle diapir and asthenospheric upwelling. The phase differences between the base-averaged field gradient and the field itself at the base point, as well as the phase differences on the ends of this base, as the most noise-proof gradient functions, are calculated for them. Based on the comparison of the experimental and model frequency curves, it is concluded that the mantle diapir fits best the experimental data, at least, in the southwest part of the Baikal rift zone.