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Among the important parameters determining the likelihood of occurrence of significant damage to engineering structures during an earthquake are the dynamic and seismic characteristics of the structures such as natural frequency, damping coefficient, and vulnerability index of the structure. In this article, the Nakamura method is applied to investigate the seismic stability of an earth-filled dam wall and the surface layer using microtremors. Measurements were taken at seven points on the dam crest and three poin...

The analysis of the dynamic and fractal properties of the released seismic energy time series allows for the classification of the seismotectonic system that produces earthquakes as a deterministic-chaotic system. The dynamics of such systems suggests that relatively small changes can lead to significant (with one or more order large) jumps. At the same time, the size of these jumps and the intervals of time that separate them are irregular, and the possibilities for their prediction are limited or absent. In this...

The present study focuses on the assessment of station corrections for eleven seismic stations from the national network of National Operative Telemetric System for Seismological Information (NOTSSI). Station corrections are obtained by calculating the ratio of the spectrum of the horizontal components of the signal to the spectrum of the vertical component (H / V). Records of S-waves from 20 local and regional earthquakes are analyzed. The values of A0 - site-effect and f0 - resonant frequency were obtained. Acco...

The study of seismicity in the Black Sea region is of particular interest for assessing the vulnerability of the surrounding coastal zones to strong earthquakes and their consequences. The seismicity pattern in the area is determined by the geodynamic processes along the boundaries of the Eurasian, Anatolian and Arabian tectonic plates. The paper presents an approach to assessing the seismic activity of the Black Sea and the surrounding region covering historical and recent seismicity. The historical events since ...

The focus of this study is detection of the deformations of the Earth's surface caused by March 3 2021 earthquake using Differential Interferometric Radar Synthetic Aperture technique. This method takes advantage of the remotely sensed SAR data provided at no cost by ESAs’ Sentinel-1 mission which are often used for creation of topographic maps as well as for detection of ground motions. The final results of this processing deliver reliable information about the displacements caused by the mentioned events with ce...

Eleven stations of the Bulgarian seismological network - National Operating Telemetry System for Seismological Information have been used for an assessment of the stations' corrections (site effect), to account for the impact on the seismic waves of the low-density layer immediately below the seismic stations, amplifying the signal. Nakamura's method for calculating the ratio of the spectrum of the horizontal component to the spectrum of the vertical component (H-to-V) is applied. Data from 20 local and regional e...

An earthquake catalogue covering the seismicity on the territory of Bulgaria and adjacent lands for the period 2000-2020 is presented in the current study. In this catalogue are included events with magnitude equal to or larger than Mw ? 2.5. As a country, Bulgaria belongs to the Alpo-Hymalian seismic belt, it is also not absent of strong earthquakes. Bulgaria is an earthquake prone country taking in account that on its territory are recorded some of the strongest earthquakes from the beginning of the last century...

Correlation studies have been made between the gravitational field (Bouguer anomalies - G) and the magnetic field (common vector (T) and the vertical component dZ) for the territory of Bulgaria. The map data is in digital format, which makes it easier to calculate. The correlation itself is estimated from -1 to 0 and from 0 to +1, which means that a positive correlation is possible in the case of increased values of both parameters and vice versa - decreasing values are associated with reduced values. This forms a...

We analyze a series of data in the ultra-low frequency (ULF) range of geomagnetic variations, which are collected from search coil instrument and acquisition system at Panagyuriste, Geomagnetic Observatory (PAG), Bulgaria, a part of South European Geomagnetic Array (SEGMA, http://sole-terra.aquila.infn.it/it/), and data for seismic noise collected at three Bulgarian seismic stations (VTS, RZN and KDZ part of National Operative Telemetric System for Seismological Information) and three Turkish seismic stations (GOM...

We analyze the micro-seismic noise recorded at five seismic stations ? DEC, DJJ, FMP, MWC and RPV. They operate within CI: Southern California Seismic Network (SCSN), USA. The data set is collected from 01 July 2018 till 31 July 2019 and all seismic events with a magnitude Mw?4 are excluded. Our main goal is to find the effects of seismic noise synchronization between different seismic stations using data relevant to the vertical seismic components. The width of the multifractal spectrum, the spectral exponent and...