Izvestiya, Physics of the Solid Earth最新文献

Abstract—In 394 samples characterizing 266 stratigraphic levels in four Turonian–Santonian sections of the Southwestern Crimea, characteristic remanent magnetization components (ChRM) acquired at the stage of diagenesis are identified. The obtained data fix the record of the paleosecular geomagnetic variation of high amplitude (root mean square deviation S = 25.9° with a fixed cut-off angle of 45°, which is about twice as high as the model S for this latitude) in the sediments formed during ~5–6 Myr and is interpreted as anomalous behavior of the geomagnetic field in the Turonian, Coniacian, and Santonian.

Abstract

For the eastern zone of the North Caucasus, including the Terek–Caspian trough, Dagestan wedge, and adjacent structures, with the maximum coverage of the data from the Federal network of seismological observations of the Geophysical Survey of the Russian Academy of Sciences (GS RAS), the regional frequency-dependent relations are determined using the Coda Wave Decay (CWD) method to estimate the seismic Q-factor of the Earth’s crust and upper mantle. In total, waveforms from 394 crustal earthquakes with source depths from 1 to 42 km and magnitudes М from 2.2 to 5.5 are analyzed using the Coda Q module of the SEISAN software package (Havskov et al., 2020). The seismic Q estimation technique using the single-scattering model is described in detail. Recommendations are given how to practically use the obtained estimates characterizing the wave properties of different-scale volumes of the fault-block geological environment to make attenuation corrections when calculating the source spectral parameters in the eastern zone of the North Caucasus. The results of the study will help to augment the information content of earthquake catalogs, in particular, with the data on energy characteristics of seismic events (universal moment magnitude values M_w) in the most seismically active regions of the Russian Federation.

Abstract—The study estimates the impact level of storm microseisms on long-term gravimetric measurements. The gravimetric measurements were conducted at the Zapolskoe, Obninsk, and Murmansk sites using CG-5 Autograv relative gravity meters. seismic measurements were conducted simultaneously with the gravimetric measurements at Zapolskoe. The analysis of these measurements has demonstrated the feasibility of using seismic data as control information to estimate the high-frequency noise component in gravimetric data. Additional seismic information was taken from the services of the Incorporated Research Institutions for Seismology. The analysis of these data established that the attenuation of the noise component in gravimetric measurements is consistent with the data from the modeled sensitive element of the gravimeter, which utilizes seismic series as an input. The first characterization of the storm-induced background noise in gravimetric measurements at the Murmansk site is obtained. Also, the possibility of predicting measurement errors based on meteorological forecasts is ascertained, which can aid in the planning of gravimetric work.

On January 8, 2022, an M6.9 earthquake occurred in Menyuan, Qinghai, which caused surface damage. In this paper, the line-of-sight (LOS) coseismic surface deformation field is obtained by the interferometric synthetic aperture radar (InSAR) of the Sentinel-1 satellite. Constrained by the InSAR surface deformation field, a Bayesian method based on sequential Monte Carlo sampling was used to invert the geometric parameters of seismogenic faults and the distribution of fault slip. Moment magnitude of the model is Mw6.6. The earthquake was determined to occur at a left-lateral strike-slip fault. Based on the historical strong earthquake dislocation model, the PSGRN/PSCMP program was used to calculate the Coulomb stress change at the epicenter of the 2022 Menyuan M6.9 earthquake caused by the surrounding historical strong earthquakes. The results show that the occurrence of the Gulang M8 earthquake in 1927, the Menyuan Mw5.7 in 1986 and the Menyuan Mw5.9 earthquake in 2016 caused a significant increase in Coulomb stress at the epicenter of the 2022 Menyuan earthquake. The coseismic and post-seismic Coulomb stress increases were greater than 0.01 MPa. Combined analysis of this result with regional tectonic stress, allows us to conclude that the 2022 Menyuan M6.9 earthquake occurred on the dynamic background of the continuous extrusion of the Indian plate towards the Eurasian plate, and the regional historical strong earthquake activity played a significant role in promoting it. The research results provide a theoretical basis for understanding the seismogenic background and dynamic mechanism of the 2022 Menyuan earthquake.

In recent theoretical studies of the authors, some estimates of the atmospheric disturbances related to inhomogeneities of the gravity field (IGF) have been obtained. The main attention was paid to dynamic effects: disturbances of the wind field under the influence of IGF. In this paper, attention is drawn to the fact that noticeable thermal effects of IGF can also exist in the surface layer of the atmosphere. These inhomogeneities, deforming the fields of pressure, air density, and air temperature, affect the temperature regime of the boundary layer and the heat exchange of air with the underlying surface. An analytical model designed to estimate the magnitudes of these effects is considered. Based on the proposed model, an analytical solution is found for a linear stationary two-dimensional problem for perturbations caused by one horizontal harmonic of the IGF in a semi-infinite stably stratified medium rotating around a vertical axis. The temperature of the lower boundary (underlying surface) was assumed to be fixed. It was also assumed for this boundary that the no-slip and no-flow conditions are satisfied. The attenuation of all disturbances with height was also assumed. The essential similarity parameters in this problem are analogues of the Rayleigh and Taylor numbers, in which the given horizontal scale of IGF serves a spatial scale. Analytical expressions are obtained for the profiles of temperature perturbations and amplitudes of deviations of vertical heat fluxes on the surface. The latter, along with amplitudes of gravity field inhomogeneities, depend most strongly on the background stratification of the medium. In highly anomalous regions, the amplitudes of heat flux deviations, according to the estimates obtained, may reach and even exceed 1 W/m², which gives grounds for taking into account the gravity field inhomogeneities in climatic calculations and numerical models of the atmosphere.

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 rate of production of ion pairs in the atmosphere against the background of ionization of the atmosphere by radioactive gases exhaled to the atmosphere from the ground and propagating together with their short-lived daughter products. The radon flux density 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 observations and the diffusion model. The distribution of the gamma radiation dose from the earth radionuclides in the soil and the atmosphere is calculated using Gleant4 software. The propagation of the radon isotopes and their decay products in the atmosphere is calculated simulated using large eddy simulation supplemented with kinematic simulation of subgrid flux of a passive scalar. It is shown that depending on the specific activity of radionuclides in the ground, the soil parameters, and the turbulent regime of the atmosphere, the total contribution of gamma 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.

An algorithm for optimizing the trajectories and movement sequence of a fleet of marine seismic survey vessels in solving the problem of marine seismic surveys using bottom stations is presented. The algorithm is based on solving the traveling salesman problem with mixed deliveries and collections of goods (TSPDC). A description of the algorithm extension to a problem that takes into account static closed zones that simulate ice and meteorological conditions unsuitable for the ship movement is given. The Dubins path algorithm provides a path close to the minimum and takes into account real characteristics of the ship movement and its speed when performing various types of work (installing bottom stations, collecting stations, maneuvering, etc.). The scientific novelty of the study lies in applying the solution of the TSPDC to problems of marine geophysics with the condition of presence of closed zones and developing an algorithm for optimizing the work of seismic vessels with the use of bottom stations, which is relevant in the conditions of the Arctic shelf during the period of limited navigation. The algorithm described in the article makes it possible to take into account the return of the vessel for collecting the equipment when working with bottom stations in the transition zone. The developed algorithm for planning marine seismic surveys formed the basis of the application software. The formalization of the problem, the results of the algorithm operation, and examples of planning on test data are presented. The possible limitations for the proposed algorithm are raised. The obtained results are applicable for further use in the implementation of tasks on optimizing the work plan for marine seismic surveys with several vessels, both when planning seismic surveys and when adjusting plans directly on the ship. The use is also justified if it is necessary to reenter the profile (for example, when reworking out a defective work area).

In this paper, we present the first results of complex geological and geophysical studies of active tectonics in the northeast of Taymyr that were 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 Taymyr 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 showed the high efficiency of application in the Arctic to identify young fault-fold structures, which are potential sources of strong earthquakes.