Izvestiya, Physics of the Solid Earth最新文献

In this paper, we determine the location of the hypocenter and the magnitude of the earthquake of September 11/23, 1888 based on macroseismic data published in the Russian periodic in Russian, Armenian, and Georgian languages. Calculations showed that the magnitude of the earthquake was previously significantly underestimated, due to which 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 M_w = 6.6 that occurred almost 100 years later confirms the long-term activity of the Western branch of the East Anatolian fault zone.

This study is devoted to application of some new statistical methods to analysis of the spatial structure of the seismic field in a seismically active region in the neighborhood of Japan bounded by the following coordinates: 28°–50° north latitude, 130°–150° east longitude. The estimates of the seismic flux were obtained by using the k-nearest neighbors method for the magnitude interval m ≥ 5.2. The highest values of seismic flux 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 km and larger in the zones with a weak intensity. It has been shown that the seismic filed parameters—intensity λ, slope of the magnitude–frequency graph 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 magnitude–frequency graph (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 М_max = 9.60 ( pm ) 0.41 was obtained with consideration of the correction for bias.

In this paper, we kinematically analyze the movements of plates and blocks of the region of southeastern Turkey, where strong earthquakes occurred on February 6, 2023, based on a homogeneous database of displacement velocities of GNSS permanent monitoring stations. Along the East Anatolian fault zone from 2008 to 2018, the Arabian Plate was established to shift relative to the Anatolian Plate, which corresponds to a left shift (without a normal component) at a rate from 1 cm/yr in the eastern part to 0.8 cm/yr in the western part. Along the Chardak fault, displacements corresponding to the left shift occurred 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 M7.8 event 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.

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 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.

The paper presents the results of the processing of satellite radar images acquired by the TerraSAR-X satellite using the persistent scatterer method for analyzing the subsidence of the earth’s surface over potash mines in the city of Berezniki, Perm Krai. A sequence of processing procedures in the GAMMA Software package (Gamma Remote Sensing AG, Switzerland) is presented, which showed good results in the conditions of this territory. A comparison is made with the results obtained earlier by summation of interferograms. In contrast to the methods of persistent scatterers, the summation is performed without analyzing displacements in time. The noisy time series obtained by the summation are not rejected, so the displacement maps cover the study area more evenly. In the persistent scatterer method, the time series is analyzed using a variety of criteria, so the subsidence rates are estimated more reliably. In the areas where the results were obtained by summation and the persistent scatterer method, the subsidence rates are in good agreement. The persistent scatterer method has made it possible to estimate displacements in certain areas separated by vast incoherent woodlands, on which interferograms lose their coherence. At the same time, a new subsidence area was identified with an average rate of subvertical displacements up to 75 mm/year and, in some areas, up to 100 mm/year, which, according to data for 2020 and 2018, was not detected. The subsidence here should be clarified based on the images for subsequent years or using surface thechniques. The time series also show the deceleration of subsidence in spring on persistent scatterers located on buildings and infrastructure. We associate the total spring deceleration of subsidence by 3–5 cm not with underground but with seasonal factors, specifically with the heating of buildings in the spring. Other reasons are also possible, but the main one is that, in areas with a moderate subsidence rate, this effect can lead to some underestimation of the average subsidence rate. A detailed study of the time series for subsidence makes it possible to identify areas requiring special attention. Most of the subsidence occurs more or less evenly; in a significant part of the territory, the subsidence rate in 2021 has decreased. This indicates the effectiveness of the measures taken to protect the ground infrastructure. Within the city area, the acceleration of subsidence was found only at the beginning of Lenin Avenue. SAR interferometry is an effective tool for studying subsidence processes in the city of Berezniki. This method significantly complements geodetic works, since it provides data on vast areas that cannot be covered by detailed ground measurements. In addition, part of the closed territories becomes dangerous for ground works, so there is no alternative to satellite technologies.

The magnetic effects of two similar underwater earthquakes with magnitudes of 6.0 and 7.3, which occurred on March 16, 2022, were considered in (Adushkin et al., 2023). According to the data of INTERMAGNET magnetic observatories, these earthquakes were found to be accompanied (with a delay of ~55 min) by variations in the Earth’s magnetic field in the form of a train of quasi-periodic oscillations with an amplitude of ~2–8 nT and a period of ~30 min at distances of ~210 to ~3000 km from the epicenter. It was suggested in the aforementioned study that this magnetic effect is caused by a disturbance of the geodynamo as a result of the impact of seismic waves propagating deep into Earth. This interesting hypothesis requires a detailed discussion from different points of view. A more detailed analysis of the pattern of geomagnetic field disturbance at all latitudes, performed by us, leads to a conclusion that the found quasi-periodic disturbance is a mid-latitude response to auroral electrojet variations and is not related to the earthquake. According to our estimates, variations with a source at the core–mantle interface on a time scale less than one year cannot manifest themselves on the Earth’s surface at all.

This paper introduces PMTools (https://pmtools.ru), a novel cross-platform open-source web application designed for the analysis of paleomagnetic data. Our software offers a user-friendly interface and supports the most commonly used data formats in paleomagnetism, including .pmd, .dir, .pmm, .rs3, .squid, .vgp, and .gpml. It encompasses all the necessary functionalities for principal component analysis of natural remanent magnetization and computing mean paleomagnetic directions along with corresponding virtual geomagnetic (paleomagnetic) poles. PMTools facilitates the application of various paleomagnetic tests to user data, such as the fold test, conglomerate test, and reversals test. Notably, the application allows for seamless import and export of paleomagnetic data (tables) in formats compatible with .csv and MS Excel. Additionally, all generated figures can be exported as high-quality vector graphics in .svg format, specifically designed for direct integration into publications and presentations. Furthermore, PMTools enables the export of sets of paleomagnetic poles in GMap and GPlates software formats, enabling researchers to promptly use their paleomagnetic data for paleotectonic reconstructions. PMTools has an intuitive interface, customizable hotkeys, and an extensive array of graph elements, all of which contribute to making PMTools an appealing, cutting-edge tool for processing and analyzing the results of paleomagnetic studies.