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Vol 2023, No 6 (2023)
Articles
From the Editorial Board of the Izvestiya, Physics of the Solid Earth Journal
Abstract
On February 6, 2023, catastrophic earthquakes struck Turkey, causing extensive destruction and numerous casualties. These seismic events immediately captured the attention of the global geophysical community, leading to the emergence of preprints and articles analyzing various aspects of the earthquakes on the Internet and in print. The Izvestiya, Physics of the Solid Earth journal also received submissions from Russian scientists containing the results of their geophysical investigations related to the Turkish earthquakes. Consequently, the editorial board of the journal decided to dedicate a special issue to this topic. This issue features articles by Russian scientists from academic institutions and universities: Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences (IFZ RAN); Institute of Earthquake Prediction Theory of the Russian Academy of Sciences (ITPZ RAN); Institute of Geosphere Dynamics of the Russian Academy of Sciences (IDG RAN); Geological Institute of the Russian Academy of Sciences (GIN RAN); Kola branch of the Geophysical Service of the Russian Academy of Sciences; Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN); the Faculties of Physics and Geology at Moscow State University; Gubkin Russian State University of Oil and Gas; as well as colleagues from Firat University in Turkey.
The articles included in this issue cover a wide range of subjects.
The geological situation and tectonic position of the earthquakes are described in the article by H. Çelik et al., along with the seismic rupture parameters obtained through fieldwork conducted in the earthquake’s epicentral zone by researchers from the Geological Institute of the Russian Academy of Sciences in collaboration with Turkish colleagues. D.A. Simonov and V.S. Zakharov present the results of a preliminary seismotectonic analysis based on GNSS observations in their article. Yu.L. Rebetskii’s article presents the tectonophysical zoning of seismogenic faults in Eastern Anatolia based on estimations and analysis of Coulomb stresses.
R.E. Tatevosyan et al. provide insights into the historical earthquake of 1888 along the northeastern extension of the East Anatolian faults, including an estimate of its magnitude.
A.I. Filippova and A.S. Fomochkina developed models of displacements in earthquake sources based on surface seismic waves, while V.O. Mikhailova et al. utilized satellite interference data on displacements on the Earth’s surface. O.V. Pavlenko and V.A. Pavlenko investigated the effects of radiation directivity of earthquake sources.
V.B. Smirnova et al. present the results of a posteriori analysis of seismic regime anomalies preceding the earthquake in Turkey. S.V. Baranova et al. offer an earthquake aftershock hazard assessment using an automated system previously developed by the authors.
The articles by V.V. Adushkin et al. and S.A. Ryabova et al. consider the geomagnetic and geoelectric effects induced by the Turkish earthquakes.
Special Issue Editors V.B. Smirnov P.N. Shebalin
3-4
Tectonic Aspects of the East Anatolian 06.02.2023 Earthquake in Turkey
Abstract
Abstract
—During the East Anatolian earthquake with Mw = 7.8, which occurred on February 6, 2023 at 1:17 UTC, the 361 km long segment of the NE-trending East Anatolian active left-lateral fault zone (EAFZ) was activated. A left-lateral displacement took place at a distance of 318 km on formed seismic ruptures. Its maximum magnitude of 8.5 m is registered northward of the earthquake epicenter. To the northeast, the displacement of several meters is maintained over a significant length of the activated segment and is accompanied by uplift of the south-eastern side of the ruptured zone at up to 1.5 m. To the southwest of the maximum displacement area, the strike slip decreases from it at shorter distances compared to the northeastern part and the vertical component varies, although the southeastern side is mostly uplifted. In the terminal southwest, the strike slip is replaced by normal faults, gaping fractures, and other manifestations of transverse extension, which are accompanied by landslides and are mainly secondary seismic dislocations. Left lateral slip also occurred at the northern ends of the western and eastern branches of the Dead Sea Transform (DST), adjacent to the EAFZ from the south. Despite the fact that the energy distribution of numerous aftershocks along the EAFZ is generally proportional to the distribution of offsets on seismic ruptures, the slip on the EAFZ occurred during and immediately after the main shock. In the northern part of the DST, a significant decrease in the amount of energy released by strong earthquakes during the last centuries has been established. We consider that the tectonic stress accumulated in the northern part of the DST became the important geodynamic source of the East Anatolian 02.06.2023 earthquake.
5-23
Preliminary Seismo-Tectonic Analysis of the Catastrophic Earthquake in South-Eastern Turkey on Feb 6, 2023
Abstract
Abstract
—In this paper, we carried out a kinematic analysis of the movements of plates and blocks of the region based on a homogeneous database of displacement velocities of GNSS permanent monitoring stations for the region of southeastern Turkey, where strong earthquakes occurred on February 6, 2023. Along the East Anatolian fault zone from 2008 to 2018, the Arabian Plate was established to shift relative to the Anatolian Plate, corresponding to a left shift (without a normal component) at a rate of 1 cm/yr in the eastern part to 0.8 cm/yr in the western part. Displacements occurred along the Chardak fault, corresponding to a left-hand strike-slip fault, at a rate of less than 0.7 cm/year. The revealed kinematics is confirmed by focal mechanisms and cosesismic displacements of the studied earthquakes. The M7.5 earthquake that occurred directly on the Chardak fault is not an aftershock of the M7.8 earthquake, but is a relatively independent event. An analysis of the seismic regime shows that the stresses on the East Anatolian fault after the main event M7.8 are relieved by the first large latitudinal fault zone (the Chardak fault). The results of our study suggest that the counterclockwise rotation of the Anatolian and Arabian plates associated with the opening of the Red Sea Rift is most likely decisive for the general kinematics of the plates in the region.
24-36
Tectonophysical Zoning of Seismogenic Faults in Eastern Anatolia and February 6, 2023 Kahramanmaraş Earthquakes
Abstract
Abstract—The results of the tectonophysical reconstruction of stresses in the crust of Eastern Anatolia, obtained from the analysis of data on earthquake focal mechanisms, have shown that a significant restructuring of the stress state has occurred here in the last 20 years. It was largely confined to the southern and southwestern sectors of the region, covering hundreds of kilometers along the East Anatolian Fault. The data obtained from tectonophysical monitoring not only on the orientation of principal stresses, but also on their normalized values made it possible to calculate Coulomb stresses on faults. The results of fault zoning by intensity and sign of these stresses helped identify both hazardous sections close to the limit state and safe sections with negative Coulomb stress values. It has been established that in the region of the source of the first strong Pazarcık earthquake, which had a complex structure (three segments), there were extended sections with a critically high Coulomb stress level, separated by zones with low and even negative values of these stresses. The epicenter of this earthquake was located on the echelon fault within a section (first segment) with a high Coulomb stress level. The source of the second strong Elbistan earthquake was located on a fault with negative Coulomb stresses. The conducted analysis shows that this second Turkey earthquake may have been caused by stress changes that occurred in the crust of the region after the first strong earthquake. The research results show that Coulomb stresses in systems of closely located and differently oriented faults may be prone to sudden changes during the development of the earthquake on one of hazardous sections.
37-65
Historical Earthquake on the North-Eastern Extension of the East Anatolia Fault
Abstract
Abstract
—The position of the hypocenter and the magnitude of the earthquake of September 11/23, 1888 were determined based on macroseismic data published in the Russian press in Russian, Armenian and Georgian. Calculations showed that the magnitude of the earthquake was previously significantly underestimated, which is why it was not included in the catalog of strong earthquakes in the Caucasus test region [Shebalin and Tatevossian, 1997]. The accuracy of the location of the hypocenter makes it possible to identify the active fault with which the source of the 1888 earthquake is associated. The earthquake with Mw = 6.6 that occurred almost 100 years later confirms the long-term activity of the Western branch of the East Anatolian fault zone.
66-76
Reconstruction of Co-Seismic and Post-Seismic Processes for the February 6, 2023 Earthquake in Turkey from Data of Satellite SAR Interferometry
Abstract
Abstract
—Using different methods for processing SAR images from the Sentinel-1A satellite, the displacement fields were determined in the region of the East Anatolian Fault Zone (EAFZ) and the Sürgü-Çardak faults, as well as a small fault on the continuation of the East Hatay fault zone, which rupture initiated a series of catastrophic earthquakes in Turkey on February 06, 2023. DInSAR and offset methods were applied. The most detailed data on the displacements were obtained by the offset method using images from the descending orbit. When constructing the model from the available SAR data, the data with the maximum signal-to-noise ratio were selected. For the northern part of the region, above 37.4° N, the range displacements obtained by the offset method from a descending orbit were used. South of parallel 37.0° N, we used azimuth displacements from the same descending orbit. The model of the seismic rupture was constructed on the basis of solution of (Pollitz, 1996) of the problem of deformations at the surface of a layered spherical Earth caused by along dip and strike displacements on a rectangular cut located inside the planet. Pollitz (1996) demonstrated that ignoring the spherical layering of the planet leads to errors up to 20%, with the largest errors occurring in the presence of a large strike-slip component. Ignoring sphericity also introduces an error when using the solution in the framework of the idealization of an elastic homogeneous half-space with a flat free boundary (Okada, 1985) which was used when constructing USGS and (Barbot et al., 2023) models. In our model the surfaces of seismic rupture are approximated by 19 rectangular elements along the strike, divided into three levels along the dip. Another element approximated a rupture along the extension of the East Hatay Fault Zone. As in the models of other authors (USGS; Barbot et al., 2023), in our model in the southern part of the EAFZ, the displacements increase from south to north, and are mainly concentrated in the upper part of the Earth’s crust to a depth of 10 km. At the southern end of this rupture, displacements in our model with an amplitude of up to 2 m are obtained at the lower levels of the model, and at its upper level, the displacements were only 0.11 m, and in this area on February 20, 2023 an earthquake of magnitude 6.3 occurred with a hypocentre depth of 11.5 km. The main displacements on the EAFZ are determined on its central segment. Here, the displacements go to a greater depth, their value reaches 10.2 m. On the Sürgü-Çardak fault, significant displacements occurred down to a depth of 20 km; displacements exceeded 9.8 m. In our model, at the northeast end of the seismic rupture along the EAFZ, a displacement area of 6.8 m overlaps with the southwest end of the seismic rupture model of the Doğanyol-Sivrice earthquake of January 24, 2020 with Mw 6.7, published on the USGS website. Therefore, our model does not confirm the hypothesis of the presence of a seismic gap here, which, according to (Barbot et al., 2023), is a zone of a possible nearest earthquake.
77-88
Source Parameters of Strong Turkish Earthquakes on February 6, 2023 (Mw = 7.8 and Mw = 7.7) from Surface Wave Data
Abstract
Abstract
—Based on the amplitude spectra of surface waves, the source parameters of the strong Turkish earthquakes of February 6, 2023 (Mw = 7.8 and Mw = 7.7) were calculated in two approximations: an instantaneous point source and an elliptical shear dislocation. As a result, rupture planes were identified, data were obtained on the scalar seismic moment, moment magnitude, focal mechanism, and source depth of the considered seismic events, and the integral parameters characterizing the rupture geometry and its development in time were estimated. It is shown that the sources of the earthquakes under study were formed under the influence of the regional stress field and their focal mechanisms were left lateral faults with a strike direction close to the strike of the East Anatolian fault zone for the first event and close to the strike of the Sürgü-Çardak fault system for the second. For the first earthquake, our estimates of the rupture duration and its length (t = 52.5 s, L = 180 km) probably refer not to the entire rupture, but only to its main phase, confined to the northeastern segments of the East Anatolian fault and characterized by maximum displacements and values of the released seismic moment. The values of t = 30 s and L = 180 km that we obtained for the second earthquake fully characterize the entire rupture.
89-102
Rupture Directivity Effects of Large Seismic Sources, Case of February 6, 2023 Catastrophic Earthquakes in Turkey
Abstract
Abstract—An overview of the results obtained by foreign seismologists based on the records of Turkish seismic networks AFAD (State Agency for Disaster Management under the Ministry of Internal Affairs) is presented. The sequence of earthquakes began with the M7.8 main shock and includes thousands of aftershocks. The strongest events occurred in the first twelve hours, with the sources of two M7.0+ events located 100 km apart. Earthquakes have caused ground motions that are destructive to structures, the so-called “pulse-like waveforms”, and epicentral distances, as was previously noted, are not a good indicator of attenuation of waves from earthquakes with extended ruptures. The records of stations in the near-fault zones clearly revealed the directivity effects of seismic radiation. The M7.8 earthquake (main shock) was larger than expected in the current tectonic setting. The near-field records traced an early transition to the super-shear (~1.55Vs) rupture propagation on the Narli lateral fault, where the rupture originated and then passed into the East Anatolian fault. The early transition to the super-shear stage obviously contributed to the further propagation of the rupture and the initiation of slips on the East Anatolian fault. A dynamic fracture model has been constructed that matches the various results of inversions obtained by different authors and reveals spatially inhomogeneous rupture propagation velocities. Super-shear velocities exceeding the shear wave velocity Vs are observed along the Narli lateral fault and at the southwestern end of the East Anatolian fault. Since the late 1990s, seismologists have been working on incorporating the rupture directivity effects of extended sources into the probabilistic seismic hazard analysis procedures, but no consensus has been reached so far, and progress in this area can only be expected with the accumulation of a sufficient amount of observational data.
103-121
The RTL Anomaly of Seismicity before the February 6, 2023 Earthquake in Turkey
Abstract
Abstract—Based on the data from the regional Turkey earthquake catalog and the ANSS Comprehensive Earthquake Catalog for Turkey and a part of Iran, a posteriori analysis of RTL anomalies of seismicity before the damaging Mw7.8 Pazarcik earthquake in Turkey of February 6, 2023 and, for comparison, before the Mw 7.1 earthquake of October 23, 2011 (Eastern Turkey), the Mw 7.3 earthquake of November 12, 2017 (Iran), and the М 6.7 earthquake of January 24, 2020 (the East Anatolian Fault), was made. Distinctly observable before the Pazarcik earthquake is an RTL anomaly with well-marked stages of a seismic quiescence and subsequent activation near the epicentre of the future earthquake. Spatially, the anomaly is one-and-a-half times smaller than the source of the Pazarcik earthquake, and one-and-a-half - two times smaller than RTL anomalies before other regional earthquakes with a magnitude above 7. By size, it corresponds to the anomaly before the Mw 6.7 earthquake that occurred on the same fault. As a hypothesis to explain why the size of the anomaly before the Mw 7.8 Pazarcik earthquake does not match the sizes of the anomalies characteristic of M7+ earthquakes, it was assumed that the detected RTL anomaly reflects the formation only of the first, relatively small segment of the source of the Pazarcik earthquake.
122-132
Automated Assessment of Hazards of Aftershocks of the MW 7.8 Earthquake in Turkey of February 6, 2023
Abstract
Abstract—This paper analyzes the use of the automated aftershock hazards assessment system (AFCAST) through the example of a series of aftershocks of the Mw 7.8 earthquake in Turkey of February 6, 2023 (the Pazarcik earthquake). The paper presents automated estimates of the aftershock activity area, the magnitude of the strongest aftershock, and the duration of the hazardous period, yielded using data on the main shock and on the first aftershocks.
133-141
Geophysical Effects of a Series of Strong Earthquakes in Turkey of February 6, 2023
Abstract
Abstract—During a series of destructive earthquakes in Turkey on February 6, 2023, in particular, two strong earthquakes with magnitudes 7.8 and 6.7 immediately following each other, the results of instrumental observations of microbaric and geomagnetic variations made in the surface layer of the atmosphere, as well as variations of the electric field and the critical frequency of the regular F2 layer of the ionosphere are presented. It is shown that the earthquakes were accompanied by variations of magnetic and electric fields, generation of infrasound waves recorded at a considerable distance from the sources, as well as variations of the critical frequency f0F2.
142-152
Response of the Lower and Upper Ionosphere to Earthquakes in Turkey on February 6, 2023
Abstract
Abstract—Ground-based magnetometers and ionospheric radio probing by means of GPS were used to analyze and interpret specific variations of the geomagnetic field and the total electron content of the ionosphere during strong catastrophic earthquakes in Turkey on February 6, 2023. It is shown that the ionospheric responses to these earthquakes recorded at distances of 1200–1600 km from the epicentre in the lower ionosphere and at distances of up to 500 km from the epicentre in the upper ionosphere can be interpreted in terms of the propagation of the Rayleigh seismic wave and atmospheric waves – shock, acoustic and internal, that is, those waves that are generated by the earthquake itself. The energy of seismic events was estimated from the ionospheric response.
153-162
Application of New Statistical Methods to Estimation of the Seismicity Field Parameters by an Example of the Japan Region
Abstract
Abstract
—This study is devoted to application of some new statistical methods to analysis of the spatial struc-ture of the seismic field in the seismically active region in the Japan region bounded by the following coordinates: 28°–50° north latitude, 130°–150° east longitude. The estimates of the seismic flux by using the k nearest neighbors method for the magnitude interval m ≥ 5.2. The highest values of intensity of about 10–4 \(\frac{1}{{{\text{year}}{\kern 1pt} - {\kern 1pt} {\text{k}}{{{\text{m}}}^{{\text{2}}}}}}\) are located at depths of down to 100 km and manifest themselves in the neighborhood of the Tohoku megathrust earthquake. The spatial resolution of the intensity estimates is ranging from 33–50 km in the regions with a high intensity to 100 км and larger in the zones of weak intensity. It has been shown that the seismic filed parameters – intensity λ, slope of the graph of repetition β, maximum possible magnitude m1 – have different scales of their spatial variability and, thus, it is necessary to apply different scales of spatial averaging to them. Based on the Gutenberg—Richter truncated distribution model, the estimates are obtained for the slope of the graph of repetition (b-value) and the upper boundary of the distribution m1. An original method is proposed for determining the optimal averaging radius for an arbitrary cell of the space grid. The method is based on the use of the statistical coefficient of variation of the corresponding parameter. For the considered region, the estimate of the maximum possible magnitude Мmax = 9.60 ± 0.41 was obtained with consideration of the correction for bias.
163-174
On Constructing Analytical Models of the Magnetic Field of Mercury from Satellite Data
Abstract
Abstract
—A new method is proposed for analytical description of the magnetic field of the Mercury from the data of satellite missions based on the local and regional versions of the linear integral representation method. The inverse problem on finding the sources of the field is reduced to solving ill-conditioned systems of linear algebraic equations with an approximately set right-hand part. The charts of the isolines of the z-component of the magnetic inductance vector in the Cartesian coordinate system rigidly connected with the planet, as well as the regional S-approximation of the field radial component are plotted. The results of the mathematical experiment on analytic continuation of the magnetic field towards the sources are presented.
175-189
Ponderomotive Forces of Alfven Waves in the Earth’s Magnetosphere
Abstract
Abstract
—This paper is devoted to the 80th anniversary of the discovery of Alfven waves, which play an important role in physics, radiophysics, astrophysics, and Earth physics. The emphasis is on the ponderomotive redistribution of plasma in the Earth’s magnetosphere under the action of Alfven and ion-cyclotron waves. At relatively small distances from the Earth the ponderomotive force is buoyant, i.e., is directed upwards, regardless of whether an Alfven wave propagates towards the Earth or away from it. In the near-equatorial zone of the central regions of magnetosphere waves in the Pc 1 range push the plasma to the minimum of geomagnetic field, so that a maximum of plasma density arises on the equator at a sufficiently high wave intensity. A bifurcation occurs at the magnetosphere’s periphery, and the maximum is split into two maxima, the distance between which increases while moving away from the Earth. The polar wind, acceleration of heavy ions, and fictitious nonlinearity of the surface impedance of the Earth’s crust are also briefly discussed.
190-198
Results of Estimating the Absolute Gravimetric Measurements at the Ledovo Fundamental Gravity Station and on the First Order Gravimetric Network of Russia
Abstract
Abstract
—This work is aimed at estimating the long-term continuing measurements of the acceleration of gravity at the Ledovo fundamental gravity station and first order stations of the gravimetric network of Russia. The observations are carried out by absolute gravimeters beginning from the mid-1970s to the present time. It is shown that the observed value of the acceleration of gravity at the Ledovo station has a tendency to decrease during last 45 years; according to our estimates, the value decreased by 32 µGal. The measurements carried out at first order gravity stations in Russia after renewal of network maintenance are compared with measurements carried out in the 1980s.
199-206
Active Tectonics of North-Eastern Taimyr (Byrranga Mountains) and Questions of Seismo-Tectonic Regionalization of the Russian Arctic
Abstract
Abstract
—In thus paper, we present the first results of complex geological and geophysical studies of active tectonics in the northeast of Taimyr, carried out during the expedition of the Northern Fleet and the Russian Geographical Society in 2020. At the foot of the Byrranga Mountains, a wide zone of active fault-folded tectonic deformations was identified and studied. The general kinematics of displacements is reverse-thrust with signs of shear. The structural style of young tectonic deformations bears a direct resemblance to well-studied structural analogues of the Central Asian seismic belt. The Taimyr seismotectonic zone reveals both spatial and genetic isolation. It has an individual model of the Late Cenozoic geodynamic evolution and modern seismotectonic regime, which differs sharply from the Laptev Sea rift zone adjacent to the east. A complex of geological and geophysical methods has shown high efficiency of application in the Arctic to identify young fault-fold structures, which are potential sources of strong earthquakes.
207-223
Variations of Geomagnetic Paleointensity Recorded in the Archeological Ceramics of the Late Bronze and Early Iron Ages in the Central Russian Plain
Abstract
Astract—The paper reports petromagnetic and archeomagnetic studies of ceramic fragments of the Late Bronze and Early Iron ages from archeological sites of the Grishinskii Istok III, Tyukov hillfort, and Shishkino hillfort, which are located in the Oka River basin, Ryazan district, Russian Federation. In total, 43 determinations of geomagnetic field intensity were obtained for the time interval of 1500–400 B.C., including 10 determinations for ceramics of the Grishinskii Istok III, 11 determinations for ceramics of the Tyukov hillfort, and 22 determinations for ceramics of the Shishkino hillfort. The studied time interval is characterized by the elevated values of the geomagnetic field intensity of 55–59 μT, which are much higher than the average field intensity for the Russian Plain in the IV–first half of III millennium B.C. Obtained VADM values for central Russian Plain fall in a wide range of values obtained on the Georgian archeological sites located in the same longitudinal sector. A large scatter of data can be related both to the large error in 14C determination, which is comparable with the duration of the best studied time interval, and with the high rate of magnetic field variations within this time interval.
224-244
Contribution of the Photonic Component to the Ionization of the Atmosphere by Earth Crust Nuclides and Radioactive Emanations
Abstract
Abstract—We investigate the contribution of gamma radiation of natural radionuclides constituting the Earth crust, radioactive emanations, and their decay product in the ground to the intensity of production of ion pairs in the atmosphere against the background of ionization of the atmosphere by radioactive gases flowing to the atmosphere from the ground and propagating together with their short-lived daughter products. The density of the radon flux to the atmosphere is estimated by three methods: the reservoir method, the integration of altitude profiles of volume activity of radon, based on gamma spectroscopic observation and diffusion model. The distribution of the gamma dose rate dose from the earth radionuclides in the soil and in the atmosphere is calculated using Gleant4 software. The propagation of the radon isotopes and their decay products in the atmosphere is calculated using large eddy simulations supplemented with kinematic simulations of the subgrid transport of a passive scalar. It is shown that depending on the specific activity of nuclides in the ground and the turbulent regime of the atmosphere, the total contribution of the γ-radiation to the ion pair production rate in the atmospheric boundary layer is approximately from 1% to 20% and increases upon a decrease in the penetrability of the upper ground layer for radioactive emanations.
245-258
On Determination of the Electrical Conductivity of a Local Inclusion of Piecewise-Constant Isotropic Medium
Abstract
Abstract
—This work is a continuation of the authors' research on solving inverse problems of mathematical geophysics in a linear formulation. Unlike previous works, where the solution was built on the basis of volumetric integral equations, boundary integral representations and emerging boundary integral equations are used here to solve the inverse coefficient problem of geoelectrics to find the constant electrical conductivity of a local isotropic inclusion, located in a piecewise-constant electrical conductivity isotropic enclosing medium.
259-268