Radan Ivanov, Emil Oynakov, Irena Aleksandrova, Mariya Popova, Jordan Milkov – EVALUATION OF THE FUNDAMENTAL FREQUENCY AND DAMPING OF A CAST-IN-SITU REINFORCED-CONCRETE BUILDING BY AMBIENT NOISE ANALYSIS

DOI: 10.35101/prg-2023.1-2.1

Earthquakes are among the most significant natural phenomena with highly negative social and economic consequences. The behavior of building structures during earthquake, the ensuing damage and other side effects are extremely important for all large cities. The dynamic characteristics of structures – predominant frequency and damping ratio used to assess the vulnerability of buildings, are most conveniently determined by analyzing ambient vibration data, as opposed to the more expensive and time-consuming traditional methods of Experimental Dynamics. In the present work, the damping ratio and the fundamental frequency are calculated by the RDM (Random Decrement Method). A bandpass filter with filter parameters chosen according to the predominant frequency obtained by the FSR (Floor Spectral Ratio) method is applied to the signal before the actual RDM processing. The results obtained by the RDM method are compared with those obtained by the FSR method. The investigated structure is the building of the National Institute of Geophysics, Geodesy and Geography (NIGGG), to the Bulgarian Academy of Sciences, which is a five-floor, cast-insitu RC building. Ambient noise measurements of 100 samples/second were made at ten locations on each floor using ETNA 2 mobile accelerometers.

Keywords: Fundamental Frequency, Structural Damping, Ambient Vibration, Damping Ratio

Emil Oynakov, Irena Aleksandrova, Maria Popova – SPATIAL AND TEMPORAL VARIATION OF SEISMICITY IN BULGARIA BASED ON THE EARTHQUAKE CATALOG (1981–2019)

DOI: 10.35101/prg-2023.1-2.2

This study statistically analyzed the earthquake catalog for the period 1981–2019, (Solakov et al., 2020). The catalog consists of earthquakes localized on the territory of Bulgaria and its surroundings area (41° – 44.6°N, 220 – 30°E; 1024 events). The present data from the earthquake catalog have been studied in two aspects – temporal variation and spatial distribution. For the region, original data were used without modification; were calculated: b-values, a-values, magnitude of completeness (Mc). A focal depth h = 0–60 km was chosen to calculate the b-values. Results obtained from a catalog with dependent events present have no statistical significance. For this, dependent events were removed using the proposed declustering technique in the Zmap software (Wiemer and Wyss, 2000). Magnitude completeness Mc was calculated using the maximum curvature method (Wiemer and Wyss, 2000). The residual catalog obtained after declustering, including 625 events with Mw ≥ 3.2, is used to estimate various parameters characterizing the temporal and spatial seismic activity in the spatial extent of the catalog (b-value, a-value, etc.).

Keywords: Catalogue, declusterization, b-value, magnitude completeness (Mc)

Marian Varbanov, Kristina Gartsiyanova, Atanas Kitev, Stefan Genchev – ASSESSMENT OF RIVER WATERS QUALITY THROUGH THE COMBINED USE OF DIFFERENT INDICES (BY FOLLOWING THE EXAMPLE OF THE TOPOLNITSA AND LUDA YANA RIVERS)

DOI: 10.35101/prg-2023.1-2.3

The article presents the possibilities for combined application of heterogeneous indices for the assessment of the quality/pollution of river waters. For the purposes of the research, the so-called “open”, “partially open” and “closed” indices were used, which are different in their construction, algorithm and content, and include at least 10 physico-chemical indicators for assessment. Their sensitivity in regard to heterogeneous anthropogenic impact – industrial, domestic and agricultural – was tested. The obtained results testify that the evaluation indices applied in the article react in a different way to individual types of anthropogenic pressure, and in specific cases the selection of only one index could give incorrect results. The Canadian Water Quality Index (WQI) is most sensitive one, and to a significant extent the Water Pollution Index (WPI) also could be regarded as sensitive. The Bavarian pollution index is more suitable for checking primarily “domestic” pollution, which limits its independent use. The results of the research make it possible to specifically reveal the spatio-temporal characteristics, forms and scales of the pressure on surface waters in the basins of the Topolnitsa and Luda Yana rivers, where various economic activities have been carried out for many years.

Keywords: water quality, evaluation indices, water pollution, water quality indicators

Rumen Penin, Dimitar Zhelev, Atanas Kitev, Tanya Stoilkova – GEOCHEMICAL RESEARCH OF THE HEAVY METALS IN THE LANDSCAPES OF THE MILEVSKA MOUNTAIN AND CHUDINSKA MOUNTAIN

DOI: 10.35101/prg-2023.1-2.4

The main purpose of the study is to establish the total content of an association of heavy metals (Cu, Pb, Zn, Ni, Mn, Co, Cr), which are prioritized in the organized background monitoring of the natural environment. The study was conducted in the soils of the landscapes of Milevska and Chudinska Planina, located in the Kraišten Natural Geographical Region of Bulgaria. Field and laboratory studies were conducted on the collected soil samples from different horizons of brown (Cambisols) and mountain-meadow soils (Umbrosols), as well as an integral sample of anthills in characteristic landscapes of the two mountains. The interpretation of the obtained results shows a relatively increased content of trace elements Zn (149.6 mg/kg), and to a certain extent Pb (19.16 mg/kg), compared to other soils from different regions of the world and mountainous territories of the South-West Bulgaria. In some parts of the region, the soil diversity is also due to a relatively high content of lithomass in the soil profile, which is differentiated differently for each soil type. Geochemical spectra were made to establish the soil-forming rock-soil relationship, as well as the degree of differentiation of microelements in the soil horizons. The relationship between the lithogeochemical features and the soil cover is weak to moderate and is related to the specific conditions of soil formation and the established small ore occurrences in the two mountains. The association of trace elements Cu, Ni, Mn, Co, Cr is distinguished by relatively low average contents in the studied soils and confirm the background character of the studied areas in the mountains. This applies both to brown forest soils (Cambisols) and to upland-meadow soils (Umbrosols). The results of the research can be used in the construction of complex ecological monitoring in the area of the two mountains.

Keywords: heavy metals, soils, landscapes, environmental monitoring

Nadezhda Ilieva, Tamás Hardi, Stefan Genchev, Aleksandra Ravnachka1, Dessislava Poleganova, Szilárd Rácz, Boris Kazakov – SUBURBANIZATION PROCESSES IN SECOND TIER CITIES IN BULGARIA – DEMOGRAPHIC, SOCIO-ECONOMIC, AND SPATIAL TRANSFORMATION OF THE AGGLOMERATION AREAS (A CASE STUDY OF PLOVDIV AND BURGAS)

DOI: 10.35101/prg-2023.1-2.5

The main goal of this study is to explore the suburbanization process by analyzing the population dynamics, socio-economic and spatial transformation in the agglomeration areas of the second tier cities (according to ESPON’s classification) of Plovdiv and Burgas in Bulgaria. For the scope of the present study, three essential tiers of analysis have been defined: demographic transformation, socio-economic transformation, and changes in land cover. Depending on the population change trends (positive and negative) and the impact of the two main components (natural and migratory growth), a settlement typology has been done using the methodology of Webb (1963) for the 2001–2011 and the 2011–2021 periods. Subsequently, an analysis of particular social and economic indicators has been carried out in order to track the changes and highlight the differences between the urban transformation of Burgas and Plovdiv respectively. The most valuable sources for spatial transformation analysis are the geospatial databases obtained by decoding satellite images enabling the study of land cover types and their change. Currently, various information sources are available, but as far as European countries are concerned, the database created and coordinated by the European Commission under the Copernicus programme is considered the most applicable (the layers containing information on the land imperviousness), as well as the JICA data. The agglomerations of Burgas and Plovdiv differ in terms of the type and intensity of changes in land cover in the 2006–2018 period. During the entire period, the agglomeration of Plovdiv exhibits a definite prevalence of the new land cover in its periphery, at the expense of the agglomeration core, in contrast to the agglomeration of Burgas. In the case of Plovdiv, the changes in its agglomeration periphery occur at least twice as fast as those in the agglomeration core. In the agglomeration of Burgas, on the other hand, the relative share of new types of land cover prevails in the periphery during certain time periods (2006–2009 and 2012–2015), at the expense of the size of that same class of land cover in the agglomeration core.

Keywords: agglomeration area, core-periphery, suburbanization, imperviousness, land cover

Milen Velikov – ASPECTS AND EVOLUTION OF THE MOTIVATION AND SATISFACTION OF WORKERS IN BULGARIA BETWEEN 2011–2021

DOI: 10.35101/prg-2023.1-2.6

The research part cited in the article is based on a series of author surveys and studies conducted in the period 2018-2021. It is formulated in such a way as to be of benefit to both employers, different types of labor intermediaries, HR experts and hiring of personnel, as well as to economically active persons in Bulgaria. The results of these studies and their analysis will enable employers to better revise and upgrade their recruitment, management and retention processes, their development and evaluation, motivation and commitment.

Keywords: motivation, attitude, expectations, people development, satisfaction, human capital, surveys, recruitment, Labor market

Velimira Stoyanova, Boian Koulov, Bilyana Borisova, Nikolay Rachev – REVIEW OF ENVIRONMENTAL AND NATURAL DISASTER POLICIES IN THE 21ST CENTURY

DOI: 10.35101/prg-2023.1-2.7

In the last decades of the 20th century and at the beginning of the 21st century, the issue of protecting the environment and reducing the risk of adverse natural disasters around the world and in Bulgaria is very high on the public agenda. The purpose of this publication is to review research on natural disasters and policies for environmental protection around the World. European environmental policy is based on the principle of precautionary measures, preventive action, and removal of pollution at its source, as well as the “polluter pays” principle. The main topics of EU environmental policy are combating climate change; biodiversity, land use, and forestry; water protection and management; air and noise pollution; efficient use of resources and creating a circular economy, sustainable consumption, and production; decreasing the use of chemicals and pesticides in agriculture. In Bulgaria, the topic of environmental protection is also receiving increasing importance. In the latest Constitution of the Republic of Bulgaria from 1991, five articles are devoted to the protection of the environment. The main challenges for the country in this field are the implementation of EU environmental legislation and the respective policies, especially improving air quality, ensuring proper collection and treatment of urban waste and wastewater; nature protection legislation; adoption of a comprehensive program and action plan on circular economy. Given the above goals and challenges, a Decision of the Council of Ministers № 577/17.08.2018 was approved on 06.12.2018, according to which the Ministry of Education and Science set up and financed Agreement № Д0-230/06-12-2018 about starting a National Science Program (NSP), entitled “Protection of the environment and reducing the risk of adverse events and natural disasters”. The program’s purpose is to conduct fundamental and applied scientific research to ensure a sustainable, favorable, and safer living environment for the current and future population of the Republic of Bulgaria.

Keywords: climate change, earthquakes, floods, COVID 19

Yulian Tyutyunnik – RADICAL GEOGRAPHY, HISTORY AND MODERNITY (IІ)

DOI: 10.35101/prg-2023.1-2.8

The concept of radical geography emerged in the late 1960s and became very popular in America and Europe in the 1970s. «Radical geography» is a problem-oriented research topic in geographical science, united by the «concept of social justice» (D. Harvey). It has such distinctive features: a) the uniqueness of the theme itself, defined by spatial and ecological problems, which are generated by man’s violence against man and man against nature; b) signs of a «scientific underground» (V.M. Kotlyakov – V.S. Preobrazhensky); c) the «leftist» political orientation of theory and methodology. Radical-geographical intensions in culture and science have always been present. The article traces their evolution from ancient Greek antiquity to the 1970s. The viewpoint that at the historical stage of «modernity» the transformation of radical geographic ideas is conditioned by a) historical collapse of marxism as a project of future society, b) emergence of the newest egalitarian and antiestablishment doctrine «postanarchism», c) cardinal transformations of historical process connected with assertion of network principles (in a broad sense) in modern society and eschatological expectations of ecological disaster, is expressed and justified. Modern geography cannot but be radicalised.

Keywords: radical geography, human rights, social justice, networking, multiculturalism, postanarchism, environmental disaster, eschatology

Dimitar Zhelev – GEOGRAPHY AS A LIFE MISSION. PROF. RUMEN PENIN AT 65

DOI: 10.35101/prg-2023.1-2.9