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.


Morozov Yu.A.,  corresponding member of the Russian Academy of Sciences.

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Vol 2023, No 3 (2023)

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Friction as a Factor Determining the Radiation Efficiency of Fault Slips and the Possibility of Their Initiation: State of the Art
Kocharyan G.G., Besedina A.N., Gridin G.A., Morozova K.G., Ostapchuk A.A.

A conceptual state of the art review of the research on fault zone shear resistance is presented. Recent works on the subject are analyzed in the context of the approaches formulated in the authors’ presentations at the Sixth Conference “Triggering Effects in Geosystems”. The analysis of the results obtained in the last two or three decades by different research teams shows that the frictional properties of the slip zone gouge play a determining role in the rupture initiation and propagation patterns. The refinement of the methods for processing the parameters of weak seismicity, aimed at estimating the “slowness” of microearthquakes confined to a fault zone, may lead to new approaches in fault zone monitoring to derive indirect information on the material composition of a fault slip zone and, thus, on its seismogenic potential. At present, such methods may be useful in solving the problems of reducing the damage caused by man-made earthquakes.

Fizika zemli. 2023;2023(3):3-32
pages 3-32 views
Possible Seismogenic-Trigger Mechanism of Methane Emission, Glacier Destruction and Climate Warming in the Arctic and Antarctic
Lobkovsky L.I., Baranov A.A., Ramazanov M.M., Vladimirova I.S., Gabsatarov Y.V., Alekseev D.A.

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.

Fizika zemli. 2023;2023(3):33-47
pages 33-47 views
On the Difference in Physical Mechanisms of Different Depth Earthquakes and Their Ionospheric Response Patterns
Rodkin M.V., Liperovskaya E.V.

According to the paradox of seismicity, earthquakes that follow the mechanism of ordinary brittle failure cannot occur at depths below a few tens of km. Several models have been proposed to explain deeper earthquakes, but these models have not been convincingly supported by data on the depth changes in earthquake source parameters. In this paper we present the examples of seismicity cutoff at the depth level of the Earth’s crust despite the undoubted continuation of similar shear displacements at greater depths. Based on worldwide data, the changes in a number of the average parameters of the earthquakes with depth are demonstrated. The pattern of these changes is consistent with expected differences in the physical mechanisms of the earthquakes with depth and significantly refines the accepted division of earthquakes into shallow, intermediate, and deep. The difference in the physical mechanisms of the earthquakes implies a probable difference in the nature of their precursors. Based on the hourly data of the vertical ionospheric sounding station “Tokyo” for 1957–2020, differences in the character of the seismoionospheric effect are demonstrated for the earthquakes (more than 300 events) occurring at different depths and presumably having different dominant mechanisms of seismogenesis. The average amplitude of the variations in the critical frequency foF2 providing the observed anomalies is estimated to be only 2–3% of the foF2 value. The separation of earthquakes by depth increased the statistical significance of the observed seismoionospheric effect.

Fizika zemli. 2023;2023(3):48-62
pages 48-62 views
On the Mechanisms of Generation of Excessive Horizontal Compression in the Continental Crust
Rebetsky Y.L.

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.

Fizika zemli. 2023;2023(3):63-77
pages 63-77 views
Seismohydrogeological Phenomena as an Earthquakes’ Trigger Impact on Groundwater (by the Example of the Wells of the Petropavlovsk-Kamchatsky Test Site, Kamchatka Peninsula)
Kopylova G.N., Boldina S.V.

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.

Fizika zemli. 2023;2023(3):78-95
pages 78-95 views
Weak Seismicity and Strongest Earthquakes Against the Background of the Variations of -wave Attenuation Field
Aptikaeva O.I.

The paper considers the role of relatively weak earthquakes as a tool for studying the environment, including of strong earthquake process. The spatial structure of the attenuation field of several seismically active regions (of the Garm prognostic polygon in Tajikistan, Altai, the Caucasus, Eastern Anatolia, the Western Tien Shan), as well as the epicentral regions of a number of strong earthquakes, and the confinement of deepened seismicity to it are considered. It is shown that the attenuation field obtained from the short-period code of weak earthquakes in seismically active regions is inhomogeneous and consists of blocks with a high Q factor and weakened zones of strong attenuation. An uneven distribution of deepened earthquakes is noted. It is associated with the block structure: in weakened zones, their share is greater than in blocks with a high Q factor. Examples of variations in the of deepened seismic activity in weakened zones are demonstrated. It varies over time, increasing before strong earthquakes. Facts are presented that testify to the existence of a relationship between the Earth’s rotation rate and the activity of deepened seismicity. Examples are given of the activation of weak seismicity in the form of seismic swarms (series of weak earthquakes concentrated in space and time) in connection with strong events. A characteristic feature of these swarm series is the isometry of the earthquake localization areas in plan view and vertical elongation. As a rule, they coincide with weakened zones of strong absorption of S-waves. Intense localized seismicity, confined to one-dimensional volumes, is most likely associated with increased conductivity channels through which deep fluids migrate. The activation of swarm series is the result of active migration of deep fluids and an increase in fluid saturation of weakened zones. Fluids, in turn, are a catalyst for processes that lead to a decrease in the strength of rocks and the destruction of blocks in epicentral zones. In this case, the clusters to which the swarm series belong can be considered as local seismogenic zones. The appearance of compact isometric in plan and nearly vertical in section clusters of weak seismicity is often observed outside the epicentral zones of strong earthquakes. Such zones may simply be indicators of the seismotectonic situation in the region as a whole. It is assumed that a sharp change in the dynamics of atmospheric pressure during the preparation of a strong earthquake at hydrometeorological stations located in such areas is a consequence of the intergeospheric interaction of the lithosphere and atmosphere. Deep degassing seems to be one of the main mechanisms of the anomalous behavior of atmospheric pressure during the implementation of strong events. It is most active in weakened zones. The mechanisms of the impact of deep degassing on the outer geospheres remain the subject of discussion.

Fizika zemli. 2023;2023(3):96-109
pages 96-109 views
Seismic Phenomena Associated with the Eruption of a Volcano in the Area of the Tonga Archipelago on January 15, 2022
Ovtchinnikov V.M., Usoltseva O.A.

The study of changes in the seismic process associated with the eruption and the assessment of the energy parameters and structure of the wave field from seismic data is the subject of this work. Three types of disturbances are distinguished in the structure of the wave field. First of all, these are Rayleigh surface waves with an average oscillation period of 23 s, well traceable at distances up to 100 degrees. The group velocity of Rayleigh waves is 3.6–3.8 km/s. The magnitude calculated from them at stations mainly with oceanic propagation paths is Ms = 5.52 ± 0.18, and the corresponding seismic energy was on the order of Ec = (1–7) × 1013 J, and the scalar seismic moment M0 =2.4 × 1017 J. Two other types of oscillations were detected on seismic channels with a frequency band from 0.0003 to 0.1 Hz of the stations. For the first, the apparent velocity of propagation of the disturbance lies in the range of 0.28–0.37 km/s with a characteristic period of 268 s. This type of disturbance is associated with the gravitational response of the seismometer to an acoustic disturbance in the atmosphere. For the second type of seismic disturbances, the propagation velocity is 0.21–0.28 km/s with characteristic periods of 450 s on the horizontal components of seismic receivers. This type of seismic disturbance is probably caused by the interaction of the gravitational wave in the hydrosphere with the coast of the islands on which the seismic stations are located.

Fizika zemli. 2023;2023(3):110-121
pages 110-121 views
Remote Sensing of the Electromagnetic Effects of the Tonga Volcano Eruption on January 15, 2022
Gavrilov B.G., Poklad Y.V., Ryakhovsky I.A., Ermak V.M.

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.

Fizika zemli. 2023;2023(3):122-130
pages 122-130 views
Numerical Simulation of Material Ejection into the Atmosphere Induced by Oblique Impacts of Ten-Kilometer-Diameter Asteroids into the Ocean
Shuvalov V.V.

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.

Fizika zemli. 2023;2023(3):131-138
pages 131-138 views
Evolution of Sliding Along a Heterogenous Fault. A Large-Scale Laboratory Experiment.
Gridin G.A., Kocharyan G.G., Morozova K.G., Novikova E.V., Ostapchuk A.A., Pavlov D.V.

A laboratory setup was constructed in IDG RAS to investigate the process of shearing the contact of rock blocks of one-meter scale. It was used to investigate deformation processes in a fault with a heterogenous structure of the sliding interface, which contained strong contact patches – analogs of the “asperity” in the model of Hiroo Kanamori. It is shown that when a large slip occurs, the rupture, that starts in the zone of maximal deficit of interblock displacement, cuts the segments of the fault with lower effective strength, the latter being decreased in previous deformation events. Those previous events may be “slow” slips with low seismic efficiency. In nature the events that “prepare” the fault interface for a large slip may be smaller earthquakes – foreshocks, or they can be either low frequency earthquakes or slow slip events, both can hardly be detected in seismic records. Thereupon a promising diagnostic indication is the shift of the spectrum of ambient seismic noise to lower frequencies caused by the decrease of fault stiffness.

Fizika zemli. 2023;2023(3):139-147
pages 139-147 views
Concurrent Active Acoustic and Deformation Monitoring of Hydraulic Fracture in Laboratory Experiments
Zenchenko E.V., Zenchenko P.E., Nachev V.A., Turuntayev S.B., Chumakov T.K.

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.

Fizika zemli. 2023;2023(3):148-157
pages 148-157 views
The Influence of Materials Structure on the Main Features of the Fracture Process in Rocks: Discrete Elements Method and Laboratory Experiment
Hilarov V.L., Damaskinskaya E.E., Gesin I.D.

A computer model of fracture of the heterogeneous materials (including rocks) based on the Discrete Element Method (DEM) is proposed. We used the bonded particle model (BPM), various modifications of which are widely used in the study the fracture process. The material is modeled by a set of spherical particles (simulating polycrystalline grains) connected by bonds placed at the points of particle contacts (simulating grain boundaries). In BPM model, the initiation of cracks was determined by the bonds breakage, and their propagation is provided by the coalescence of many broken bonds. Computer experiments were carried out for the materials with different features (various grain mechanical properties and sizes, various mechanical properties of the grain boundaries), in order to find out the influence of these parameters on local stresses and the defect formation. Calculations were held in the MUSEN software. Cylindrical samples were filled with spherical particles of the same or different radii. The parameters of materials for grains and bonds (grain boundaries) were taken corresponding to granite, quartz, orthoclase, oligoclase, and glass. The sample was placed in a virtual press, in which the lower plate was stationary, and the upper plate moved towards the lower one at a constant velocity until the sample was destroyed. The calculation of the maximum local stresses showed that the homogeneity of material leads to greater space heterogeneity of local stresses and vice versa, heterogeneity contributes to their greater uniformity. Comparison with the results of laboratory experiments on rock deformation showed that the proposed model of polycrystalline materials realistically describes some features of their destruction when the main processes occur along the grain boundaries. These features include the brittle nature of homogeneous materials fracture and the presence of nonlinear elasticity (plasticity) for ones that were more heterogeneous. For heterogeneous materials, the model demonstrates a two-stage character of fracture process, when at the first stage the accumulation of defects occurs uniformly over the sample, and at the second stage – the formation and growth of the fracture site.

Fizika zemli. 2023;2023(3):158-167
pages 158-167 views
The Influence of Mining Operations on Seismic Activity of the Rocks in Underground Mines of the Khibiny Massif
Kagan M.M., Kozyrev A.A., Motorin A.Y., Streshnev A.A.

The issues of the causes and factors of manifestation of seismic activity during the extraction of minerals in the deposits of the Khibiny massif, which are mined underground, are considered. Based on seismic monitoring data, groups of seismic activity were identified, such as seismicity in the working area, directly related to blasting and natural seismicity, related to other mining and geological factors. The difference in the characteristics of the manifestation of seismicity for these two groups of seismic events is shown.

Fizika zemli. 2023;2023(3):168-178
pages 168-178 views

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