DOI: 10.3897/geostudies.3.e195608

Authors: Michael Ohakwere-Eze

Abstract: Traditional seismic inversion often struggles to differentiate sandstone reservoirs from surrounding shales in the Niger Delta due to overlapping P- and S-impedance contrast. This study utilizes Poisson Impedance (PI), optimized through the Target Correlation Coefficient Analysis (TCCA) method, to overcome these limitations. By iteratively correlating the PI curve with Gamma Ray (GR) and Water Saturation (Sw) logs, optimal rotation factors, c values were determined to isolate lithological and fluid properties, such that the value which gave the maximum correlation coefficient for GR and Sw were used to derive two new attributes namely Lithology impedance (LI) and Fluid Impedance (FI) respectively. The results identified an optimal c value of 1.324 for Lithology Impedance (LI) (max correlation: 0.758) and 1.296 for Fluid Impedance (FI) (max correlation: 0.633). Cross-plot analysis of these derived attributes successfully separated sand-shale facies and identified hydrocarbon-bearing zones. Application to pre-stack seismic data produced LI and FI volumes consistent with well-log observations, indicating that TCCA-derived Poisson Impedance is an effective tool for high-resolution reservoir characterization in complex deltaic environments.

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DOI: 10.3897/geostudies.3.e194004

Authors: Michael Arvanitis

Abstract: Active geothermal systems in the Mediterranean occur in a tectonically diverse belt shaped by subduction, slab rollback, back-arc extension, active faulting and Quaternary volcanism. These settings offer an excellent natural laboratory for integrated geophysical monitoring because the same systems combine deep heat sources, structurally controlled permeability, clay alteration, complex fluid phase changes and strong near-surface heterogeneity. This review evaluates the complementary roles of seismic methods, magnetotelluric and controlled-source audiomagnetotelluric imaging, self-potential, transient electromagnetic methods and ground-penetrating radar for the exploration and monitoring of Mediterranean geothermal fields. A new practical synthesis case study for Campi Flegrei is included to move beyond a purely narrative review: it compares method sensitivity, depth of investigation, uncertainty sources and decision value using original review-level plots and a transparent scoring matrix. Representative examples from Milos, Nisyros, Santorini, Etna, Ischia and western Anatolia are used to test transferability across different geothermal play types. The review concludes that future progress in Mediterranean geothermal characterization will depend less on any single technique than on uncertainty-aware integration of geophysical, geological, geochemical and geodetic information, supported by explicit reporting of resolution and alternative interpretations.

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DOI: 10.3897/geostudies.3.e193286

Authors: Kamelia Petkova

Abstract: Spatial segregation is a key characteristic of contemporary urban development and reflects deep social and economic inequalities. Roma communities are among the most vulnerable groups affected by processes of spatial isolation, often concentrated in peripheral and socio-economically disadvantaged areas. Despite the growing body of scientific research on the topic, there is a lack of a systematic overview of the development, structure, and thematic focus of the field. This study aims to present a comprehensive bibliometric analysis of scientific publications on spatial segregation in urban environments, with a focus on Roma communities, for the period 2020–2026. The analysis is based on data extracted from the Dimensions database and applies a combination of descriptive and network-based methods implemented through VOSviewer. The results indicate a growing scholarly interest in the topic, characterized by an interdisciplinary nature that brings together sociology, human geography, and urban studies. The co-occurrence analysis of terms identifies three main thematic clusters: classical studies on segregation and ethnic groups; theoretical approaches from social and urban geography; and economic and transformational processes in urban environments. Citation and co-citation analyses reveal a fragmented structure of the scientific field, characterized by the absence of a dominant theoretical framework and the presence of multiple interconnected research strands. The overlay visualization demonstrates a clear evolution in thematic focus—from earlier studies related to housing conditions and descriptive analyses to more recent research addressing spatial policies, public spaces, and institutional mechanisms, with an increasing emphasis on Roma communities. The findings confirm that spatial segregation is a multidimensional and dynamic process shaped by the interaction of social, economic, and spatial factors. This study contributes to the literature by systematizing the scientific field and identifying emerging research directions, thus providing a foundation for future interdisciplinary and applied research. It also advances bibliometric scholarship through a broader conceptual scope, framing spatial segregation as a multidimensional urban process.

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DOI: 10.3897/geostudies.3.e176708

Authors: Plamena Raykova, Dimcho Solakov, Stela Simeonova

Abstract: Strong earthquake with moment magnitude MW7.5 hit the city of İzmit, Turkey with devastating effect in August 1999. The earthquake occurred in the North Anatolian Fault (NAF),and was followed by an intensive aftershock activity. It is assumed that the studied earthquake is a part of a seismic sequence that started in 1939 along the North Anatolian Fault. Over a period of 60 years or more, a series of large earthquakes moved progressively from east to west by the fault. The analysis of the space-temporal pattern of seismic clusters (foreshocks and aftershocks) distribution of the 1999 Turkey earthquake, is presented in the research. The properties of aftershock sequence (distinct cluster in space and time) allow for a time-dependent prediction of aftershock probabilities. Aftershock activity can sometimes cause more destruction than the main earthquake, due to factors such as radiation pattern, location and the cumulative nature of building damage. If the distribution of aftershocks over time is considered as a non-stationary Poisson process, the maximum likelihood method is used to estimate the parameters of the modified formula of Omori - power-low decay. A transformation from the time scale t to a frequency-linearized time scale τ is applied to test the correspondence between different statistical models and the occurrence of an aftershock sequence. As a final step of the study, a criterion - Akaike’s information criterion is used to determine the best model for the temporal distribution of aftershocks.The results of the study show that the precursor aseismic gap before the August 1999 MW7.5, Turkey earthquake is not observed. The aftershock sequence shows a complex temporal pattern - one secondary aftershock sequence with a different value of p – parameter.

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DOI: 10.3897/geostudies.2.e180731

Authors: Nadezhda Ilieva, Kamelia Petkova

Abstract: This study examines the transformations in fertility among Roma living in urban settings in Bulgaria by combining demographic data, a large-scale quantitative survey, and in-depth interviews. The findings reveal that despite the traditionally high fertility rates and favourable age structure characteristic of the Roma population during the 1990s and the early 21st century, the last two decades have been marked by a distinct decline in both overall fertility and adolescent childbearing. Changes in reproductive behaviour are shown to result from a complex interplay of socio-economic conditions, migration processes, educational trajectories, shifting family roles, and religious influences. The data demonstrate a strong association between the number of children, educational attainment, employment status and income levels, with higher levels of education and economic stability correlating with planned parenthood and smaller family size. At the same time, the large-scale migration of young Roma abroad exerts a dual effect: on the one hand, it generates a demographic vacuum at the local level, and on the other, it transfers norms of postponed parenthood and limited fertility. The interviews highlight increasing female emancipation and the growing role of education as an internal regulator of reproductive decision-making. The article argues that fertility should not be conceptualised as an isolated demographic characteristic, but rather as a reflection of social inequalities and the dynamic processes of adaptation within Roma communities.

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DOI: 10.3897/geostudies.2.e159500

Authors: Brenda Araújo, Adriana Brambilla, Elídio Vanzella, Felipe Gomes do Nascimento, Priscila Fernandes Carvalho de Melo

Abstract: The addressed theme focused on the importance of online reviews in contemporary hotel industry, emphasizing the crucial role customers play in sharing their opinions and experiences through review platforms. Therefore, the research aimed to contribute to the improvement of hotel services by highlighting the relevance of perceived quality in various aspects, such as location, comfort, cleanliness, cost-benefit, and Wi-Fi availability. In this context, the main objective of this article was to analyze the most present positive and negative factors in online reviews of hotels in the Cabo Branco district, Paraiba. Regarding the methodological approach, reviews of hotels listed on the Booking and TripAdvisor platforms were collected and analyzed, focusing on the Cabo Branco district, PB. The results revealed that location, cleanliness, and Wi-Fi quality emerged as the main positive aspects highlighted by customers, while cost-benefit and the amount paid for the service were pointed out as the main negative factors. For future research, it is recommended to conduct longitudinal studies to monitor the evolution of reviews over time, as well as a more in-depth investigation into the factors that influence customer satisfaction in the hotel industry. This includes aspects such as organizational culture, customer experience, and technological innovations. These approaches can provide valuable insights for the development of effective management strategies and the improvement of hotel service quality.

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DOI: 10.3897/geostudies.2.e145909

Authors: Alessandra Souza Queiroz Melo, Cláudia Araújo de Menezes Gonçalves Martins, Elimar Pinheiro do Nascimento, Marilia Ferreira Paes Cesário

Abstract: The objective of this study was to investigate how gastronomic tourism has been approached in academic productions both nationally and internationally. The research used a qualitative methodology, with emphasis on bibliographic research, carried out on the journal portal of the Coordination for the Improvement of Higher Education Personnel (CAPES). The search was directed to the period from 1990 to 2022, in order to gather the theoretical support necessary to deepen the understanding of the theme. 25 articles that were most aligned with the object of study were selected. The results indicate that scientific research on gastronomic tourism is recent, covering a period of about three decades, with different approaches and perspectives. The presence of convergent and divergent points was found between the articles, addressing aspects such as cultural identity, symbolic values and socioeconomic development. However, the main focus of the research was the analysis of the materials and methods used in the selected academic productions, which allow us to understand the most recurrent methodological approaches in the investigation of gastronomic tourism.

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DOI: 10.3897/geostudies.2.e126114

Authors: Petar Stavrev, Petya Trifonova, Metodi Metodiev

Abstract: Analysis and solution of the forward magnetic problem for models of disjunctive layered geological structures, such as faults and layer discontinuities, are developed in this paper. Magnetic anomaly components Z, H, T, ΔT and Ta resulting from disjunctive geologic structures are similar to those caused by thin-layer magnetic sources of finite size. Structures of a discontinuous horizontal layer, an up-thrown fault, inclined, normal or reverse faulted, an over-thrusted structure and also a thick-layer fault of the relatively small throw are examined. The composition of different forward magnetic models of disjunctive structures and their calculations can be facilitated by the applied specific properties of thin layers with unlimited depth extent. A method of rotation is proposed to analyse the anomalous magnetic effects caused by discontinuous crustal structures. The results shown are useful in analysing field magnetic data, recognising sources, inverting anomalies and interpreting geophysical data.

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DOI: 10.3897/geostudies.2.e145652

Authors: Ramom Santos Custódio, Adriana Brambilla, Elidio Vanzella, Felipe Gomes do Nascimento, Priscila Fernandes Carvalho de Melo

Abstract: The hotel industry is facing an increasingly competitive market in which customer loyalty is crucial to gaining a competitive edge and increasing profitability. Loyalty programs are valuable strategies for customer retention, especially in an environment of high competition and high acquisition costs. In this context, the general objective of this research was to analyze the loyalty programs used by the hotel sector in João Pessoa, Paraíba, Brazil. As far as the methodological procedures are concerned, this paper was characterized as descriptive, with a qualitative-quantitative approach, under a field study. Data was collected by applying a questionnaire to 10 hotels located on the beaches of Cabo Branco and Tambaú. The results indicated that, in many cases, there is a growing use of technology and marketing tools to improve customer relations and increase the attractiveness of loyalty programs, especially the use of CRM and e-mail marketing. However, there are significant challenges, such as high costs and a lack of technological integration, which prevent these programs from reaching their full potential. It was suggested that future studies analyze the impact of omnichannel strategies and the use of artificial intelligence in the management of loyalty programs.

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DOI: 10.3897/geostudies.2.e144761

Authors: Daiko Lima e Silva, Marília Ferreira Paes-Cesário, Felipe Gomes do Nascimento, Kennedy Kaufummam Costa Mafra, Simone Neto de Santana Oliveira

Abstract: The world lives in the age of the internet, real-time information, and a growing appreciation and concern for diversity across all areas of society. As a result of these transformations, discussions about the rights of people with disabilities and the challenges they face in navigating urban spaces and participating in various activities, including everyday tasks that should be guaranteed by law, as well as sports and leisure activities, have become more prominent. In this context, this study aimed to assess the accessibility conditions for people with disabilities at Joaquina Beach in Florianópolis, the capital of Santa Catarina, located in southern Brazil. This research is characterized as exploratory and descriptive, with an applied nature, and qualitative analysis. It was organized into two stages: a theoretical phase, including bibliographic and documentary research as primary investigative strategies, and a field phase, based on the application of a checklist to assess accessibility conditions on beaches. The checklist covered the following aspects: 1) Support points for specific assistance for people with disabilities; 2) Access routes; 3) Communication and signage; 4) Parking spaces for vehicles; 5) Toilets; and 6) Beaches. The results indicate that Joaquina Beach currently does not offer satisfactory accessibility conditions for people with disabilities or reduced mobility. Therefore, it is necessary to encourage and implement public policies that can provide better conditions for accessing the beach and waterfront facilities, ensuring greater autonomy and freedom for all individuals.

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DOI: 10.3897/geostudies.1.e137361

Authors: Nadezhda Ilieva, Boris Kazakov, Desislava Varadzhakova

Abstract: Ghettoised urban structures form an essential component of the urban environment wherever they are found and their distinctive physical traits make them clearly identifiable. In the present study, various theories, concepts and viewpoints – mostly of European and American scientists – have been examined and the theoretical aspects of the term "ghetto" have been outlined through the prism of the Bulgarian reality – based on the example of the Roma neighbourhood of Harman Mahala in the City of Plovdiv. The main research question to which an answer is sought is: are the Roma neighbourhoods in Bulgaria essentially ghettos and how many of the characteristics of the ghetto do they exhibit? The study is based on a survey amongst 500 inhabitants of Harman Mahala or 27.8% of its population, as well as on in-depth, semi-structured interviews, with representatives of local authorities, educational and health mediators from the studied Roma neighbourhood school principals, teachers and students. Through the application of the so-called checklist method, it was established that the studied Roma neighbourhood meets all but one condition (Involuntary segregation), in order to be referred to as a “ghetto” and, therefore, it can only be regarded as a “ghettoised urban structure”.

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DOI: 10.3897/geostudies.1.e133185

Authors: Emil Oynakov, Mariya Popova

Abstract: The present study comprehensively analyzes seismic events recorded by the National Operative Telemetric System for Seismological Information (NOTSSI) in 2023. Seismic data are collected in real-time by 26 Bulgarian stations, supplemented by numerous stations from neighboring countries, enhancing the precision of hypocentral location determinations. The main kinematic parameters and the magnitude of the earthquakes are estimated utilizing an adaptation of the product HYPO’71. In the practice of NOTSSI, two types of magnitude estimates are used. Magnitude MP is determined by measuring the maximum amplitude of the P wave. The seismic moment magnitude MW is estimated from the seismic moment M0 - a quantity that combines the rupture area and the residual displacement along the fault with the strength properties of the medium (shear modulus µ). The present study transforms MP, into the more reliable and widely used magnitude scale MW.MW allows for homogenizing the magnitude estimates in the available seismological information and creating a homogenized catalog. The energetically homogenized catalog ensures compatibility of the input seismological information and a reliable assessment of the energetic distribution of earthquakes. The year 2023 was remarkable for the two devastating earthquakes, magnitudes M7.8 and M7.5, that occurred in Eastern Turkey on February 6th, followed by more than 40 000 aftershocks. They caused human losses and enormous material damage. Although they were more than 1500 km from the territory of Bulgaria, the main shocks were partially felt on the high floors of some buildings.The earthquakes analyzed in Bulgaria and its surroundings in 2023 were primarily low-magnitude events with uneven spatiotemporal distribution. The hypocenters’ depth distribution was in the upper levels of the earth’s crust. The largest number of events were registered in the Rilo-Rhodope seismic area, which covers the Struma and Rhodope seismic zones. The highest concentration of seismic events is observed again in the Struma seismic zone. In the Srednogorie region, along the Maritsa River valley, on June 7, 2023, occurred the strongest earthquake for 2023. It had a magnitude of 4.8 and an intensity of 6.5 in the epicentral area.Looking at the overall picture of earthquakes in Bulgaria in 2023, we should also note the weak seismic events in the Burgas and Strandzha regions in Southeastern Bulgaria and the region of Northwestern Bulgaria.For the last five years, 2023 has been characterized by the highest seismicity, as measured by the number of registered events (68 with MW>3) and the highest magnitude (MW4.8).

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DOI: 10.3897/geostudies.1.e120103

Authors: Yulia Kroumova, Tanya Trenkova, Stoyan Nedkov, Aleksandra Ravnachka

Abstract: In the contemporary digital world, data is a pivotal capital considered an economic factor for generating digital products and services. The rapid growth in data volume and their heterogeneity requires optimization of the data management in order to extract higher added value from them. In the context of this issue, one of the goals of the National Scientific Program “Environmental Protection and Risk Reduction from Adverse Events and Natural Disasters” is the creation of a unified geo-informational environment integrating the data from the work packages. To realize this goal, the present study examines certain aspects of data quality related to their usability. By reviewing basic standards for geospatial data, the metadata paradigm, and previous experience in data quality assessment, a theoretical framework with the main stages of a methodological approach evaluating the suitability of primary data sources for building a unified geoinformation database has been developed. The research results reflect the application of developed criteria systems (detailed and generalized) in analyzing the quality and the study of the suitability degree of selected information resources for one of the Program’s working packages. The results of extensive surveys from work program packages have been generalized. Selected primary data sources have been catalogued, and a multicriteria methodological approach has been developed to assess their quality in terms of their suitability for the unity of the database.

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DOI: 10.3897/geostudies.1.e115530

Authors: Neli Jordanova, Diana Jordanova

Abstract: Identification of magnetic minerals, which determine the magnetic properties of natural rocks, sediments and soils, is of crucial importance for any further interpretation of their magnetic signature in environmental or paleogeographical context. One of the major and widely used methods for determination of kind of magnetic phases in natural materials is by obtaining the Curie/Neel temperature of the respective magnetic mineral. In this contribution, we report a set of thermomagnetic measurements of high-temperature behavior of magnetic susceptibility for topsoils from the territory of Bulgaria, aiming to reveal the pedogenic and lithogenic signature. The data are considered and reported in respect to the parent rock type. Our results suggest that pedogenic magnetic minerals are represented mainly by fine-grained maghemite and/or hematite with possible Al-substitutions in the crystal lattice. This phase is expressed on the heating run of the thermomagnetic curve as a “hump” with a maximum at 250–300 °C. Coarse-grained magnetite is identified as a dominant lithogenic magnetic mineral. Hematite’s presence in a sub-set of red-colored soils is confirmed by additional analyses of isothermal remanence acquisition curves. Two hematite coercivity components were identified, related to pedogenic and lithogenic origin, respectively.

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DOI: 10.3897/geostudies.1.e113477

Authors: Vladimir Ivanov, Reneta Dimitrova, Ivelina Georgieva, Georgi Gadzhev, Kostadin Ganev, Nikolay Miloshev

Abstract: According to future climate projections, the expected thermal stress environmental conditions will get worse if the authorities do not apply appropriate measures for mitigation and adaptation to these changes. The health issues concerning air pollution and extreme temperatures have assumed great importance in recent years. The objective of this study is to estimate the thermal comfort in two of the biggest cities in Bulgaria - Sofia and Varna and their surroundings for the year 2017 by biometeorological indexes. We use computer simulations of the atmospheric parameters that define the thermal comfort indexes, by Advanced Research Weather Forecast Model WRF ARW version 3.9. We performed the simulations on four domains for 2017 with an output frequency of 1 hour. The outermost domain has a horizontal resolution of 9 km and encompasses the Balkan Peninsula. It uses initial and boundary conditions from the 0.25-degree NCEP Final Operational Model Global Tropospheric Analyses datasets with a time-frequency of 6 hours. The estimation of the thermal comfort conditions is performed with characteristics called indexes. The differences in the number of cases between the indexes are due to the specific definitions and the meteorological factors that each of them takes into account. Some of these characteristics have applications depending on the specific thermal conditions.

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DOI: 10.3897/geostudies.1.e109372

Authors: Kostadin Ganev, Georgi Gadzhev, Ivelina Georgieva, Vladimir Ivanov, Nikolay Miloshev

Abstract: Bulgaria has developed national emission reduction strategies for the period from 2020 to 2029 and the years after 2030, in accordance with EU Directive 2016/2284. Our fundamental aim in this study is to assess the effects of the strategy on the PM near surface concentrations in Bulgaria. All the simulation was done by the modeling system U.S. Environmental Protection Agency (US EPA) Models-3 for 2008 to 2014 period and with 9 km horizontal grid resolution for the selected region – Bulgaria. The meteorological background that was used is with 1°x1° resolution from the National Centers for Environmental Prediction (NCEP) Global Analysis Data. There are 5 emission scenarios structured: 2005 emissions (reference period), 2020–2029 emissions projected with existing measures (WEM) and with additional measures (WAM), projected after 2030 WEM and WAM emissions, as parallel calculations were performed with all of the scenarios. Making parallels between the concentrations, with different scenarios simulated, gives the possibility to evaluate the national emission reduction strategies’ effect.

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DOI: 10.3897/geostudies.1.e115877

Authors: Marina Raykova, Alexander Naydenov

Abstract: Tourism is a very important sector for the Bulgarian economy with its GDP share varying between 10 and 13% before the COVID-19 health crisis. In 2021 domestic tourism accounted for 89% of the personal travel expenditures of Bulgarians. The purpose of the present paper is to analyse public attitudes towards the domestic leisure tourism in Bulgaria and its spatial distribution at the NUTS-2 regions and the residence place type level. The data used in the research are from a national representative survey based on a two-staged random sample stratified by the Bulgarian districts and the residence place type (capital, district administrative centre, town and village). The methodology includes: literature review, descriptive analysis, spatial analysis, average values, building one- and two- dimensional frequency distributions, statistical hypothesis testing, etc. The indicators used in the paper are: practices for domestic leisure tourism, stay duration in domestic resorts, frequency of domestic leisure tourism, people not practicing domestic leisure tourism, domestic leisure tourism average satisfaction level. The obtained results show the differences between those indicators in NUTS-2 and residence place type level, as well as between summer and winter leisure tourism. The presented results are of particular importance, since some of these differences are significantly large.

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