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11th Congress of the Balkan Geophysical Society
- Conference date: October 10-14, 2021
- Location: Online
- Published: 10 October 2021
41 - 60 of 86 results
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Shear-wave Velocity Database as key Input for Seismic Site Amplification Models in Bucharest City, Romania
Authors A. Bala and D. Toma DănilăSummaryThe contribution of local site effects to seismic hazard is significant in cities located on thick stack of loose Quaternary layers of sediments such as Bucharest City. Here, strong-motion recordings of major intermediatedepth Vrancea earthquakes in 1986 and 1990, as well as the disastrous effects of previous major earthquakes (in 1940 or 1977) proved the necessity and importance of microzonation maps not only for new building design, but also for a great part of Bucharest old buildings stock, which is in a critical need for urgent retrofitting. Some studies emphasized the conclusion that mean shear-wave velocities (Vs) corresponding to the main 7 geological layers in the Bucharest underground: i) are important and must be known until deeper depth of 100- 150 m, making Vs-30 an insufficient and obsolete proxy for the explanation of spectral acceleration peaks at surface (Bala et al., 2014); ii) in surface the values of Vs may vary considerably across the city in just a few hundreds of meters.
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Time Series Analysis of Monthly sea Level Data at Varna Tide Gauge Station
Authors A. Ivanov and I. GeorgievSummaryThis article contains time series analysis of tide gauge data to solve for short and long-term sea-level variations at the Varna tide gauge station. The period of observation is 1928 – 12.2020.
Тime series data includes average monthly sea level data corrected for subsidence of the tide gauge staff. Applied methods are Single spectrum analysis, Fourier, and Least-squares linear regression model. Determining the mean sea level and trend plays a key role in determining the results of global warming.
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Infrared Spectral Measurements of Quartz, Malachite and Hematite in Interpretation of Remote Sensing Data
Authors D. Borisova and M. GoranovaSummaryInfrared spectral measurements as a part of remote sensing are used in mineral deposit investigations. The objective of the present paper is to compare infrared spectral measurements made in laboratory and spectral data from USGS spectral library. In the present investigations laboratory spectral reflectance measurements of quartz, malachite and hematite in the infrared range (2–25 micrometers) of the electromagnetic spectrum are performed. The obtained data of the performed spectral measurement could be used for filling in the database and for better interpretation of satellite data. This work is supported by Bulgarian National Science Fund under Contract number KP-06-M27/2 (КП-06-М27/2).
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Joint Interpretation of Dissimilar Geophysical Data from Philippi, n. Greece, Using the Curvelet Transform
Authors A. Karamitrou, G. Tsokas and A. StampolidisSummaryImage fusion between different types of overlapping data offers significant advantages in archaeological research. For example, it complements the information that exists in images from dissimilar geophysical methods, enhances elusive yet systematic features and can reduce the effect of noisy spurious signals. Such improvements allow the identification of buried structures of archaeological importance with higher accuracy and greater confidence. In this work we use the curvelet transform to combine geophysical images from different modalities to detect possible archaeological targets in Philippi, Northern Greece. We jointly interpret overlapping data from two surveys, one utilizing the method of magnetic gradiometry and another measuring the apparent electrical resistivity. The images show several possible rectangular anomalies whose dominant orientation lies along the azimuths of 0 and 90 degrees which coincide with prior knowledge about this region. We utilize one of the main advantages of the curvelet domain that is the ability to express the imaged features as a function of their orientation and wavelength and we produce fused images that exploit the prior information about dominant building orientations. Our initial results are promising, showing several prominent features and possible excavation targets with sharp rectangular boundaries that possibly depict buried masonry of archaeological interest.
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Uniaxial Deformations Estimation in the Vrancea Area Based on GPS Data
Authors N.D. Mateciuc and A. BălăSummaryThe present paper aims to analyze the state of crustal deformation in the Vrancea area using GPS measurement data. Unlike previous approaches that used station networks, uniaxial deformations method on profiles has now been used. A brief description of the extended Vrancea network was made, whose nodes were used to draw the measurement alignments. For each subnet Northern Vrancea and Southern Vrancea respectively, separate alignments were drawn, the analysis being carried out for each subnet separately. The analysis takes into consideration 21 alignments, 8 in the Northern Vrancea subnet and 13 in Southern Vrancea subnet. The results are presented in the form of result tables, in which the uniaxial strains and the variation of the angle with respect to the North direction at the two moments of the determinations, t1 and t2 were determined. For each measurement alignment, a graphic representation that contains all the calculated elements was made. The conclusions refer to the characteristics of the two subnets in terms of calculated values, to the strain magnitudes and to their possible connection with the local fault system.
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Astronomy Teaching and the Impact of NEA Asteroids on Earth
Authors A.L. Boldea and M. StavinschiSummaryThis paper aims to present and implement modern training methods, as efficiently as possible, through the e- Learning platforms Moodle, Googleclass, and Mooc for teaching an Astronomy course to students. An interdisciplinary approach, Mathematics-Geography-Geophysics-Astronomy leads even more to the explanation of the phenomena of appearance and development of the Solar System, as well as to find out the data referring to the age of our Solar System, approximately 5 billion years. We propose a brief presentation of the component of our Solar System, as well as the study of other small celestial bodies, such as NEA, Near Earth Asteroids and their impact on Earth. The paper presents several applications of Astrometrica software for the detection of NEA asteroids, and which have proven to be effective and useful, using active teaching-learning methods, such as learning through investigation and discovery. Some of these mixed teaching-learning methods have been successfully used to teach astrometry and astrophysics to students at the University of Craiova, using real astronomical data obtained from the Isaac Newton Astronomical Observatory in La Palma, Spain.
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Building up a Seismic Network in the Early Days of Seismology in Romania
Authors V. Adina, M. Popa, C. Ionescu and D. PaulescuSummaryThe science of seismology is relatively new. In the last 100 years, important milestones were achieved both in the understanding of the geological particularities which influences the earthquakes occurrences and in the development of seismological instruments.
In Romania, the seismological service was founded at the end of XIX century by the initiative of some dedicated researchers in the field of astronomy, geosciences, mathematics and physics. In 1902 in Romania there were two seismological services at Bucharest and Timisoara.
Through hard work and devotement, these earthquake study initiatives extended in organizing the first seismic stations in Romania. In time, the seismic stations activity was organized in a more durable context, by creating the Romanian Seismic Network.
Nowadays, the Romanian Seismic Network has over 200 stations both in Romania and in neighboring countries, fully equipped with digital instruments of high precision.
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A Possible Seismic gap in Vrancea (Romania) Zone at Depths below 150km
Authors I. Moldovan, B. Enescu, C. Ghita, C. Ionescu and A. MarmureanuSummaryThe Vrancea seismic zone is located beneath the Eastern Carpathians in Romania and characterized by persistent, well-confined seismicity. The main seismic activity occurs at intermediate depth (60 - 180 km). The purpose of this study is to explore a possible seismic gap of seismicity, similar to that reported by Marza (1979) before the 1977 Mw 7.2 Vrancea earthquake. The earthquake data is provided by the ROMPLUS earthquake catalogue (Oncescu et al., 1999 – updated).
The results of the analysis show a clear decrease in the number of Vrancea earthquakes (Mw >= 2.5) with depths below 150 km, starting in the year 2014. The number of recording seismic stations in the eastern part of Romania, as well as in and around the Vrancea region, does not change significantly in 2014, so the decrease in the number of deep events may not be related with the station coverage. Further exploration is, however, necessary. We have also found some intriguing changes of hypocentral depth, for the same earthquake, when comparing the output of the Early Warning System (EWS), automatic and manual locations. We will further analyze the reasons behind these changes and confirm whether the current seismic gap is genuine or not.
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Tsunami Waves in the Region of Southeast Europe: Analysis and Modeling
Authors L. Dimova and R. RaykovaSummaryThe aim of this study is to review and model tsunami waves in the region of Southeastern European sea basins. The strongest earthquakes are revised using several seismic catalogues over the period 1000–2021. Tsunami data was collected from a historical catalog, as well as more recent tsunami tide-gauge records from the mareographic network. The geometry of the faults is calculated via formulas or directly taken from the European Database for Seismogenic Faults (EDSF). Thirteen seismic sources placed in the broad Eastern Mediterranean are analyzed in order to build a reliable input for tsunami simulation. Recent tsunami events in the Aegean Sea are simulated using numerical code UBO-TSUFD: 20 July 2017 (Bodrum-Kos, Mw=6.6), 2 May 2020 (Crete, Mw=6.6) and 30 October 2020 (Samos-Izmir, Mw=7.0). In all three cases the focal mechanisms favor the formation of a tsunami, as well as the generated waves were registered by several tide-gauges and a comparison between computed synthetic mareograms and observed tsunami was made.
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Importance of Post-project Evaluation and its Implementation Method - GwB Project in Serbia and BiH
Authors S. Komatina, T. Aizawa, K. Suto and J. SugawaraSummaryHeavy rain in May 2014 triggered thousands of landslides in Balkan region. In order to help in overcoming difficult situations, humanitarian expert project was performed by AGES and financially supported by SEG GwB.
The project brought students, researchers and practitioners in Serbia and BiH together with experts - volunteers from seven other countries. They cooperated towards a common goal of geophysical surveys, data analysis and design of countermeasures for landslide disaster mitigation, overcoming the divisive history of wars, race, religion and culture.
But, evaluation of geophysical surveys often accounts for the technical aspects alone, while social, economic and environmental evaluations are rarely discussed in professional societies. The importance of achieving the SDGs is increasing in all the social activities; geophysics is expected to deliver value to the world and that is why geophysical projects should be assessed in terms of social, economic and environmental impacts as in the SDGs.
Among various methods of project evaluation, the Development Assistance Committee of Organization for Economic Co-operation and Development (OECD-DAC) proposed six evaluation items. These assessment criteria are tools for business evaluation from the perspective of sustainable humanitarian benefits and often involve volunteers across national borders and set standards based on international consensus.
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Geophysical Approach for Mapping Zones of low Permeability Endangering the Stability of a Tailings dam Wall
Authors G. Georgieva, N. Stoyanov and S. DimovskiSummaryThe presented results confirm the applicability and high efficiency of the proposed integrated approach, based on the application of electrical resistivity surveys, exploratory core drilling, and wireline logging. It allows not only a reliable delineation of the studied zone of low permeability but also an evaluation of the efficiency of the installed relief wells. The acquired hydrogeological cross sections are of great importance for the development of an applicable technological solution regarding seepage control and the stability of the tailings dam wall.
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Contribution of ERT Geophysical Survey in the Study of Sediments Accumulated Inside Karstic Caves
Authors I. Fikos, G. Vargemezis, C. Pennos and J. TverangerSummaryIn this work we present the results of electrical resistivity tomography application inside two karstic caves in Macedonia, North Greece. The primary objective of this survey was the identification of the thickness of sediments accumulated in the caves. The second objective was to try to identify features in the sediments and possible unknown cavities below the floor of the chambers investigated each time. These two findings would serve to better understand the geometry of similar caves and help build realistic 3D models of caves as a possible hydrocarbon reservoir.
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Short Introduction to the Importance of Spectral Data Library
By M. GoranovaSummarySpectroscopy is the study of the interaction between matter and electromagnetic radiation as a function of the wavelength or frequency of the radiation. Spectroscopic measurements of using laboratory spectrophotometer are performed. The acquired spectra are used in creating a thematic spectral library. The used instrument working in the wavelengths (175–3300 nm) is UV-VIS-NIR Spectrophotometer Perkin Elmer Lambda 1050. An example of the performed measurements of samples of minerals is described. The acquired information from spectroscopy is supposed to be analyzed, systemized and present to the public in a user-friendly way. One of the possibility to present data as open access database is organized databases in the library. In this case the acquired spectral data could be shared in the professional community organizing the data in spectral library. Such spectral library could include also information of the input images that could be interpreted in different levels. Except the spectral data in the databases of the library different type of additional information for better analysis of images are planned to include. This work is supported by Bulgarian National Science Fund under Contract number KP-06-M27/2 (КП- 06-М27/2).
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Structure of the North Eastern Pannonian Basin, Romania, a Review
Authors I. Munteanu, I. Panea and R. RobanSummaryThis short review is focused on the understanding of the structure and evolution of the NE Pannonian Basin realm, Romania by integrating outcrop geology with geophysics data (gravity, magnetics and seismic). The Pannonian Basin open during Middle Miocene-Pliocene times as a back-arc of the Carpathians and Dinarides orogens. The extension produced several asymmetric sub-basins separated by highs, some of them made by metamorphic basement, like Codru, Ticau, Mezes and Preluca. We interpret that the metamorphic basement has been uplifted in the present-day position in the footwall of major extensional detachments which generated the accommodation space for the Neogene sediments. The basins and the highs are clearly evidenced by the Bouger gravity map, the basins are contoured by local gravity lows of up to 15–20 mGal, like in the case of the Miresu Mare Depression. The extensional system and the Neogene magmatic arc are cross-cut by a large left-lateral strike-slip fault system the Bogdan Voda Dragos Voda with a Middle Miocene horizontal displacement of around 25 km. This Middle Miocene deformation is well correlated with the emplacement of the Subcarpathian Nappe over the foreland platform and accommodates differences in shortening across the Carpathian Orogen.
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Array Electromagnetics for Reservoir Monitoring
Authors Y. Martinez, K. Strack and H. PassalacquaSummaryGeophysical methods are key for characterizing geologic formations and monitoring fluids within the reservoir. Electromagnetic (EM) methods, in particular, are sensitive to the changes of the reservoir fluids by measuring the bulk resistivity. Therefore, they are preferred for reservoir monitoring and geothermal exploration applications. A field-tested EM reservoir monitoring workflow, including 3D feasibility and field noise measurements at the study areas, has been implemented. The result of the workflow is an optimized survey configuration combined with the best performing sensors for an array system that can send recorded data to the cloud in real-time for a 24- hr turnaround for quality assessment. This remote assessment allows crews without experience in EM methods to efficiently carry out operations, increasing the EM methods development for global operations. This presentation includes examples of the workflow application to waterflood and CO2 storage monitoring. These examples validate our approach and demonstrate the value of EM methods for injection monitoring.
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Evaluating Capability of Automated Detection and Location Method for the Case of Intermediate-depth Earthquakes from Vrancea
Authors N. Poiata, D. Tataru, F. Borleanu and B. GrecuSummaryThe intermediate-depth seismicity from Vrancea seismic region in Romania represents the main source of seismic hazard for Romania and neighbouring countries, with the most recent largest events (M 7.7 and 7.4) known to have caused significant and widespread destruction. The particular characteristics of Vrancea seismogenic volume that fall into category of, so called, “seismic nests”, make it as well of great scientific interest in seismology. In this study we present first results evaluating the performance and capability of an automated network-based full-waveform earthquake detection and location scheme for building a detailed view of seismic activity in space and time with the focus on the intermediate-depth earthquakes from Vrancea seismic source Romania. We make use of case-specific synthetic examples for testing the parameters of the detection and location scheme and analysing the influence of station configuration on the accuracy of events location.
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Identifying the Possible Locations of Earthquakes M6+ in the Bulgarian Region
Authors A. Gorshkov, O. Novikova, S. Dimitrova, L. Dimova and R. RaykovaSummaryInformation on potential earthquake sources is a key issue for seismic hazard assessment. The work presents an application of the phenomenological approach for identifying possible locations of strong earthquakes in the Bulgarian region. The methodology hypothesizes the nucleation of strong earthquakes at morphostructural nodes, forming at the intersections of morphostructural lineaments, which are detected by morphostructural zoning. Based on a wide set of geophysical and geological data characterizing nodes pattern recognition algorithm Cora- 3 pinpointed capable nodes for M6+ in the Bulgarian region. Most of the recognized seismogenic nodes are located on the borders between the largest tectonic domains. They are boundaries between the Rila, Pirin, and Rhodope massifs, the Serbo-Macedonian, and the Rila-Pirin massifs as well as in the Stara Planina range. The set of characteristic features of seismogenic nodes established by recognition suggest the high contrast of neotectonic movements and the presence of deep heterogeneities in the earth’s crust in the vicinity of such nodes.
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Modulation in VHF Wireless Signals Associated With Preearthquake Processes. Case Studies for the Balkans
Authors D. Ouzunov, S. Velichkova and E. BotevSummaryWe study the atmospheric variations in the intensity of broadband wireless signal propagation correlated with preearthquake processes. We maintain ground observations in the VHF range of 1.8 -3.5GHz in Bulgaria, Southeast Europe, close to Northern Greece, and FYR since 2012. We are recently working with three EMC antennas with a receiving range of 10MHz - 6GHz and real-time processing RF Spectrum Analyzer. Our observations revealed phenomena associated with a natural enhancement of the intensity of the signals days/hours before the seismic events, even far from the observation region. We are presenting results related to several earthquakes in the Balkan area: M5.6 of May 22, 2012, in Bulgaria, M5.1 from August 12, 2018, in Albania; M4.1 from August 2, 2018, in Southern Bulgaria; and M5.5 of October 28, 2018, in Romania. The VHF antennas have registered all earthquake events in Bulgaria at a distance of between 20 and 400km. The source for the intensity intensification could be the electrical and electrochemical processes in the atmosphere presented into the regions surrounding the transmitter- EMC antennas. Some changes in the atmospheric boundary layer (ABL), triggered by an intensification of radon and other gases release, could lead to a change in lower atmosphere conductivity.
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Parameters Related to Earthquake-early-warning System for Some Seismically Active Areas in the Balkan Peninsula Region
Authors D. Dragomirov, L. Dimova and R. RaykovaSummaryThis study investigates the possibility of early warning procedures for some seismically active areas in the Balkan Peninsula using freely available seismic data. Specifically, signals from seismic events in some regions near the stations of the Virtual Seismological Network of Sofia University (VSNSU) are evaluated. A number of characteristics are estimated, including signal-to-noise ratio of P- and S-waves, amplitudes, and durations of the first trains of P- and S-waves, the difference in the arrival time of P- and S-waves, etc. Additionally, the direct relation between magnitude estimation and maximal P-wave amplitude is compiled in order to calculate the magnitude of the detected events as early as possible. Three-component records for some seismic areas are tested to localize events using the method of Golitsyn. Since most of the seismic areas in the Balkans are crustal faults, a first evaluation of the distance range between different parts of the specific fault and the location of the used station was made. Detected parameters may be used in the development of regional early warning systems in the near future.
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Application of Contemporary Technologies for Monitoring Landslides „Thracian Cliff“
Authors M. Atanasova-Zlatareva, H. Nikolov, I. Georgiev and A. IvanovSummaryThe area of research interest is an activated landslide located near the village of Topola, Kaliakra municipality and it is manifested in the front of an ancient stabilized landslide “Kalkan tepe”. The combined GNSS and InSAR applications for landslide monitoring in the north of the Black Sea coast, Bulgaria conducted in the past 3 years aimed to contribute to the complex geodetic and geological research. Due to their high precision GNSS are very appropriate for investigating geodynamic processes. The InSAR technique is a remote sensing technique mostly applied for the detection and monitoring of earth surface deformations with wide spatial coverage. In November 2020, an aerial drone survey of the Thracian Cliff landslide was performed using UAS technology to mapping surface models of the study area. The ability to observe many points (pixels), including the whole object, as well as their behavior over time, allows the development of models of the deformation process and facilitates the solution of a number of tasks on forecasting and geohazard. The application of contemporary technologies for monitoring greatly facilitates the monitoring of landslide deformation processes.
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