Seismic Instruments最新文献

The article presents the following: the results of deformation monitoring by GNSS tools at the FSUE Radon radioactive waste disposal site (Moscow oblast); a brief history of the development of the geodynamic observation network at the industrial site of Radon. the results and geodynamic interpretation of GNSS observations of Earth surface movements for 2008–2017. the results of studies on upgrading Radon’s geodynamic structure, taking into account the creation of a single digital space for the industrial site to manage its lifecycle. The article summarizes the experience in creating life cycle monitoring systems at radioactive waste disposal sites using modern digital measurement methods.

The authors have studied the characteristics of the short-period S-wave attenuation field in the lithosphere of southwest Alaska (in the Alaska subduction zone). Records of seismic station KDAK, obtained for shallow earthquakes within the distance range of ~250–750 km, were processed. We used a method that analyzes the ratio of maximum amplitudes in Sn and Pn waves (parameter Sn/Pn). The correlation dependence of this parameter on distance for wave lines crossing rupture zones of three large and great earthquakes is plotted: the Great Alaskan earthquake of March 28, 1964 (M_W = 9.2), the Simeonov earthquake of July 22, 2020 (M_W = 7.8), and Chignik earthquake of July 29, 2021 (M_W = 8.2). It was established that this dependence goes a little higher than similar dependences obtained earlier for regions of southwest Japan and central Chile, and much higher than for the region of northeast Japan. The reasons for the substantial differences of these dependences in different regions are discussed. The authors consider heterogeneities of the attenuation field in the rupture zones of the Simeonov earthquake and its largest aftershock (M_W = 7.6), as well as of the Chignik earthquake.

In his early works, the author developed a mechanical–mathematical method for modeling synthetic seismograms and accelerograms of strong earthquakes for a given site with certain ground conditions, whereby an earthquake is viewed as an effect of instantaneous rupturing of Earth’s crust. This study examines ground displacements, velocities, accelerations, and relative shear strains, as well as earthquake response spectra based on synthetic accelerograms. All ground categories are reviewed, from the hardest rocks to the most unconsolidated soils. The maximum values for ground displacements, velocities, and accelerations are obtained as a function of the attenuation coefficient of rocks and the number of oscillation modes of the considered foundation bedding, as well as peak ground accelerations as a function of distance from the expected earthquake’s rupture. It is shown that higher oscillation modes increase ground acceleration 1.66 times if calculated using only the first oscillation mode; they also increase ground displacements 1.1 times, while decreasing shear strain 1.1 times. The maximum positive attenuation effect in hard ground compared to its absence reaches 37%. Shear strain values increase proportionally to an increase in soil category number. At a level of 15 m from Earth’s surface in rocky soils, at a magnitude of М = 7.0, the shear strain values exceed the critical thresholds, which implies a high probability of surface rupturing. Response spectra obtained by synthetic accelerograms are compared to similar spectra based on a large number of actual earthquakes, showing that they are quite similar both qualitatively and quantitatively. Based on the results, it is recommended to use them for assessing seismic hazard levels in various areas, monitoring for earthquake prediction, ensuring seismic safety of facilities and underground structures, and enhancing analysis methods of seismic impact on buildings and structures.

The article presents the results of monitoring the seismic impact of bulk blasts during explosive breaking of iron ore in the Gubkin mine on the city of Gubkin. The dependence of the maximum oscillation velocity in a seismic explosion wave on the reduced (based on the mass of the explosive in the delay stage) hypocentral distance to the explosive chamber is obtained. For one bulk blast, an isoseist map was constructed, demonstrating the intensity of seismic impact on residential areas of the city. Taking into account the requirements of regulatory documents and duration of seismic and explosion vibrations, estimates of the permissible and maximum permissible velocities of seismic vibrations for the population have been obtained.

A brief analysis of different regulations for determining seismic loads based on the spectral theory shows that they have much in common but, at the same time, contain numerous amendments and clarifications for assessing true seismic effects. The calculation of seismic loads for one and the same conditions according to the regulations used in different countries produces significantly different results. According to the authors, there is a real possibility of creating common international regulations by refining and supplementing the existing ones. Apparently, the most promising regulations are European Standards EN 1998-2004/2012. The principle of calculation according to EN is more natural because seismic actions are actually transmitted to structures through a foundation. In addition, this approach allows consideration of a number of factors that affect the degree of seismic effects (ultimate shear resistance of soils, pressure on foundation soils, foundation−soil contact area, seismic beam tilt, etc.). An attempt is also made to assess the factors that impede the acceleration of building foundations during strong earthquakes.

Automated assessment of felt reports in accordance with the regionalized DYFI questionaries were implemented on mobile applications and messengers of the seismological service eqalert.ru. The new tool was tested on Sakhalin Island, which is considered as an active crustal region. We have developed a regression relationship between the peak ground acceleration and the community internet intensity for the studied area. The community internet intensity calculated from a large number of felt reports has a variance comparable to those given from a prediction equation of the physically based ground motion parameters. The given approach is considered as a state-of-art tool for the rapid collecting and assessment of macroseismic data. It may be used both with the weighted average method for generating high-quality shaking maps immediately following the felt earthquake. It is also a good way to involve the population in ground shaking measures.

This paper reports the first estimates of the characteristics of radiation and propagation of seismic waves in the Ural region obtained by modeling the accelerograms of recorded local earthquakes. The obtained source parameters are similar to those of the Caucasian region, while the seismic wave propagation characteristics are similar to those of the Baikal rift zone. A somewhat increased duration of strong motion in the Ural region can obviously be explained by a fractured structure of the Ural Mountains. The ground motion prediction equations (GMPEs) proposed by the Global Earthquake Model (GEM) project for the Ural region correspond to the platform regions with a stable continental seismicity, while the obtained characteristics of radiation and propagation of seismic waves in the Ural region correspond to the seismically active regions with a crustal seismicity. The comparison of the amplitudes of acceleration response spectra of the strongest earthquake recorded in the region with the estimates obtained by using the GMPEs has revealed a considerable excess of the estimates over the observed spectral amplitudes. Hence, the recommendations of the GEM should not be used in their original form, without correction factors, and it is necessary to develop the regional GMPEs for the purposes of seismic hazard analysis.

This paper presents the results of a detailed study of two relatively strong seismic events, occurred on November, 22, 2016 (М_W = 5.0) and April 3, 2017 (М_W = 4.8) at the northeastern flank of the Baikal rift zone in the areas of the South Muya and Kalar ranges. Both the events were followed by weak aftershocks (N = 178–539, К_р ≤ 11.0), whose epicenters were densely distributed over an area. The seismic moment tensors and hypocentral depths of the mainshocks were calculated from surface wave amplitude spectra. It has been shown that their sources were formed under the influence of the subhorizontal SE–NW extension and the subhorizontal or inclined NE–SW compression. Both the earthquakes were followed by noticeable macroseismic effects at epicentral distances up to 500 km. In the area of the Baikal−Amur Railway, their shaking intensity was IV–V MSK-64. The results obtained can be used in continuous seismic monitoring at the northeastern flank of the Baikal rift zone and can contribute to an objective seismic hazard assessment of the study area.