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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...

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...

The territory of Bulgaria represents a typical example of high seismic risk area in the eastern part of the Balkan Peninsula. The spatial distribution of seismicity in Bulgaria is uneven, which gives reason to group earthquakes into geographically defined zones - seismogenic zones. In the present study the Sofia seismogenic zone will be examined. Sofia seismogenic zone is located in southwestern Bulgaria - the area with pronounces tectonic activity and proved crustal movement. The capital of Bulgaria - the city of...

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...