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10th Congress of the Balkan Geophysical Society
- Conference date: September 18-22, 2019
- Location: Albena Resort, Bulgaria
- Published: 18 September 2019
64 results
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Preliminary results from analysis of geodetic data for the Northern Black Sea landslide “Momchilov rid”
Authors N. Dimitrov, I. Georgiev, M. Atanasova and A. IvanovSummaryThe study of landslides is of particular importance because these phenomena can lead to great material damage. Northern Black Sea coast is an important economic area and is driven by well-developed tourism. The region is affected by many landslides and it is important to monitor motions of the major landslides in the area. A preliminary study, based on data provided by Ministry of Regional Development and Public Works of the landslide processes in the area of “Momchilov rid” was made. Processed and analyzed are four epochs geodesic coordinates to solve for points velocities of the established geodetic control network.
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Preliminary results of Integrated Geophysical Surveying in an active landslide in Işıklar-Trabzon, Turkey
Authors M. Şenkaya, A.E. Babacan and H. KarslıSummaryIntegrated Geophysical Surveying has gain importance for landslide investigations, deciding the type of landslide, location of the possible sliding and failure zones, the interface between soil and bedrock, determining of water-containing zones, and lithological variation in lateral and vertical direction. This study presents preliminary results of the evaluation of seismic refraction tomography (SRT), multichannel analysis of surface wave (MASW), electrical resistivity tomography (ERT) and microtremor (HVSR) data collected in from an active landslide where is located in Işıklar locality of Maçka district in Trabzon province. From these data, 2D P-wave velocity and ERT sections, 1D S-wave velocity depth profile, and the values of predominant frequency and H/V amplitude of ground were obtained by using regular processes and inversion steps. Based on preliminary results, possible distribution of landslide materials in the horizontal and vertical directions was revealed and it is shown that the landslide materials with a thickness exceeding approximately 12 meters. Dominant materials of study area are composed of large and small blocky rocks and have a very complex structure. Moreover, the SRT and ERT sections show the presence of a valley-shaped structure and that the type of landslide is a combination of collapse-sliding.
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Rainfalls and groundwater influences on landslides in Northeast Bulgaria
Authors Y. Chapanov, M. Atanasova, T. Orehova and H. NikolovSummaryThe main reason of landslide activation is rising of groundwater, saturation by rain, water infiltration and snow melting. One part of landslides in Northeast Bulgaria starts after heavy rainfalls, as was evident during the last 20-year wet period. The interconnection between the landslides in Northeast Bulgaria, rainfalls and groundwater maxima is investigated by variations of discharge for spring near Kotel and groundwater levels in two dug wells near Balchik, precipitation from meteorological stations Sofia, Varna, Veliko Tarnovo and Kazanlak, and Palmer Drought Severity Index (PDSI). The periods of maxima of precipitation, PDSI and groundwater time series are compared with the registered occurrence of landslides. Some part of landslides occurs after groundwater maxima, other part – after intensive short-time rainfalls without significant change of groundwater levels. It is necessary to analyze time series of precipitation and PDSI in order to provide comprehensive landslide forecast. The groundwater levels follow almost exactly the PDSI variations, while the short time intensive rainfalls are presented as significant spikes in precipitation time series. The hazard risk of landslides on the territory of Bulgaria should be estimated by the maxima of PDSI, real meteorological data from stations located near the Black Sea coast and inside the territory.
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Geophysical Surveys for a Quarry Characterization - A Case Study in Konsko, Gevgelija
Authors I. Gjorgjeska and V. SesovSummaryGeophysical surveys by application of seismic refraction and shallow reflection method were carried out on the potential quarry location in Konsko, Gevgelija, R. North Macedonia.
The investigations were performed for defining of the seismo-geological structure, i.e., physical-mechanical characteristics of the rock mass constituting the structure of the terrain in conditions prior to excavation, and exploring the possibility for its use as a construction-technical material for a dam over Konska Reka river.
As a result of the investigations performed by application of seismic reflection, there were defined local disturbances and discontinuities that point to loose, cracked zones in the shallower as well as in the deeper layers of the terrain structure of the investigated location.
The seismic refraction method was used to define the variation of the Vp and Vs velocities of seismic waves down to a maximum depth of 30–50 meters. Defined with these investigations was the thickness of the surface layers composed of highly weathered and crushed rocks under the influence of external atmospheric conditions and also as a result of tectonic processes.
According to the generated 2D isopach map, the most critical zone belongs to the upper North-eastern part of the location
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Heavy rainfalls in Bulgaria due to solar activity and their possible influence on landslides
Authors Y. Chapanov, M. Atanasova and H. NikolovSummaryThe solar activity cycles affect various parameters of surface areas, including rains, snow covers, river streamflows and other hydrological cycles. These processes are due mainly to the total solar irradiance variations, followed by weather and climate changes. The interconnection between the solar cycles and decadal changes of rainfalls over Bulgaria is investigated by means of reconstructed Total Solar Irradiance TSI, precipitation from meteorological stations Sofia, Varna, and Palmer Drought Severity Index (PDSI) for the period 1899–2015. The decadal oscillations of precipitation and TSI with periods corresponding to the sunspots (11 years), solar magnetic cycle (22 years), equatorial solar asymmetry (45 years), Gleissberg cycle (70–100 years) and their harmonics are compared and analyzed. Models of decadal variations of PDSI and precipitation, based on solar cycles and harmonics, are created. The periods with rainfall and PDSI maxima are calculated on a century time span and a forecast of landslides is determined.
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Application of Electrical Resistivity Tomography and Induced Polarization for Identification of Underground Reinforced Concrete Structures
Authors I. Taleski and A. VelevskiSummaryApplicability of the Electrical Resistivity Tomography and Induced Polarization methods for detecting and identification of underground reinforced concrete structures was tested on an overpass foundation with three piers. Prime targets for this survey was detection and delineation of low resistivity and high phase angle difference zones, created by reinforced bars embeded in concrete structure. For the purposes of these investigations, 2 profiles laid along the piers were set up and joint resistivity and IP data was recorded and than processed. Interpreted sections give a very good results in detection and delineation on selected structure, which may provide valuable information that can be used in various engineerical applications.
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Detection of buried foundations in urban environment by Electrical Resistivity Tomography
Authors F. Chitea, D. Ioane, C. Tolbes, M.C. Calin and A. DiaconuSummaryDetection of buried remains of old structures is not always an easy target for electrical or electromagnetical methods as sometimes there is a low contrast between buried remains and embedded rocks or due the interference of modern infrastructure which makes difficult to isolate the buried remains signal or limits the deployment of geophysical profiles. In this paper, we present a successful case study, where local geophysical noise sources were overpassed by using ERT method. High-resolution 2D models allowed to locate buried remains of old facilities and even to reconstruct the footprint of an old building which displayed a complex “L” shape. The 3D ERT resulted model allowed to compare different sectors of the building, to extract the most probable foundation structure (different on two wings) and to analyze the construction rubble filling material.
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SEISMIC LOCATION OF COAL SEAM FAULTS IN UNDERGROUND COAL MINING
By O. SukhininaSummaryTo aid in coal seam faults exploration in the underground coal mines, a seismic location method based on multidirectional summation of reflected seam waves was developed. In contrast to the known method of controlled directional reception (CDR), it is proposed to calculate the time shifts between seismic records using not only the linear component of the hodograph of the reflected waves with a common source (or receiver) point, but also a hyperbolic component. The asymmetry of this hodograph, as well as the specifics of the placement of the seismic observation system in the mine workings, allow for a separate detection of the reflecting boundaries in the four sectors of the outer (relative to the observation system) part of the coal seam. The proposed method can be useful when a single mine working is utilized.
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Depth Estimation from Gravity Data Using Radial Amplitude Spectrum Method: Application on Dikili (İZMİR) Geothermal Field
More LessSummaryGravity method is a natural potential field method which is frequently used in geophysical investigations. The main principle of the method is to determine the buried structures in the ground by taking advantage of the changes in the vertical direction of gravity acceleration. There are many different methods developed to determine the depth of structures. In this study, the mean depth values of Bouguer gravity data obtained in Dikili district of İzmir province were determined using Radial Amplitude Power Spectrum Method (RAPSM) based on 2D Fourier transform. The greatest advantage of this method over the conventional power spectrum is that it works by determining the mean value of the cross-sections taken in different directions. Thus, it does not matter what direction the user takes the cross section and the depth of the structure can be determined more accurately. As a result of the application, the average depth values of the basement structure of the study area were determined. The topography of the basement structure varies between 320 m and 640 m in the region.
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A hidden caldera revealed from magnetotelluric data in Cappadocia region of central Turkey
Authors A.T. Basokur, N. Meqbel, Ö. Hacioglu, H.I. Arslan and T. EfeçinarSummaryA magnetotelluric survey has been conducted in the Cappadocia region of central Turkey in order to find new geothermal resources. The survey area has formerly been postulated as the location of a buried caldera that was one of the main eruptive centres of Cappadocian Volcanic Province. Three-dimensional non-linear conjugate gradient inversion of magnetotelluric data by using the full impedance tensor helps to delineate the subsurface resistivity distribution. The derived resistivity model reveals the possibility of a buried caldera. The low resistivity anomalies are interpreted as the clay alteration zones caused by hydrothermal activities.
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Processing and interpretation of geological and geophysical data for establishing the geothermal resources
Authors N. Asimopolos and L. AsimopolosSummaryA geothermal system can be described as a system in which water is used as a transport agent, through which the heat is taken from the sources from basement and transmitted to the consumer. The main elements of a geothermal system are a source of heat, tank and transport fluid, represented by water. The geothermal prospecting for the entire territory of Romania, carried out by temperature measurements allowed the development of geothermal maps, highlighting the temperature distribution at different depths and heat flow. For a good image of the Romania’s geothermal potential, we present, in our paper these maps, that made with the Surfer program, based on the data obtained through digitalizing geothermal maps of Romania (scale 1: 1000000) using Surfer software, kriging method for interpolation. Also, we made maps with other geophysical parameters after smoothed and filtrated of geophysical data (Bouguer anomaly, Free Air anomaly, geoid) and correlations between them.
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Investigation of Geothermal Potential of Balıkesir-Sındırgı-Düvertepe Area with Magnetotelluric Methods
Authors C. Sari, E. Icoz and E.G. YurtkalSummaryIt is aimed to investigate the potential of geothermal fluids to be used in the power plant. The purpose is to determine the total thickness of the sedimentary units and the basement topography, to clarify the underground structure, to identify the regions that can operate in terms of geothermal energy and the lateral discontinuities of the sedimentary units. The study was carried out in the eastern part of Sındırgı/Balıkesir Province (Turkey). 60 MT and AMT measurements were made in the area and the deep geological structure was tried to be clarified. Paleozoic metamorphic rocks and the Upper Cretaceous age series which are incompatible with them were found in the study area. Upper Miocene volcanics unconformably overlie the complex sequence. These units cover alluviums unconformably, especially in stream beds. According to the results, it was found that there were many lateral discontinuities in which the throws and directions were very different from each other. When the cross-sections were examined in terms of the resistivity distributions, it was observed that low resistivities, high-very high resistivities dominated deep in the regions near the surface. The low resistivity zones between very high resistivity blocks were interpreted as a possible volcanic activity in the area.
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Tentative oblique subduction high resolution models, lead to reducing costs of HPCC usage
Authors M. Pomeran, L. Zlăgnean and L. BeşuţiuSummaryThe Computational Fluid Dynamics (CFD), is a method of analysis which scientists and engineers are using to build high complexity models. One of the most important side problems of CFD is the cost of operating the computational infrastructure, that is increasing along with the models.
This work tries to contribute a technique of building high resolution CFD models along with reducing these operational costs. We try to rise the awareness to an understated part of the parallelization process: the mapping phase, when the bulk computing load is distributed towards the individual computing cores of a computing cluster.
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Wireless Mobile Digital Device for Ambient Noise Recording
Authors D.Z. Zlatanski and D. GospodinovSummaryA wireless ambient noise accelerometer (ANA) device for data recording, based on a tri-axial acceleration sensor, has been developed by us. The mobile device has wireless control allowing great mobile convenience. The device is designed to record microseismic ambient noise on the basis of which to analyze the fundamental response frequency at the recording site. It is based on the three component ADXL355z acceleration sensor, featuring a 24bit ADC. The applied method for the data analysis is the H/V spectral ratio technique. We performed simultaneous recordings of ambient noise at two sites with two systems – ANA and a velocimeter GBV-316. The obtained results are similar, which reveals the applicability of ANA for ambient noise recording and site effects analysis.
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Absolute magnetic measurements, methods, and instrumentation
Authors A. Domjan, L. Hegymegi and C. HegymegiSummaryAbsolute geomagnetic measurement is an accurate determination of magnetic declination D and inclination I at a given location and time on the Earth. These quantities are essential to monitor the long-term baseline changes and calibration parameters of variometers in observatories and repeat station surveys.
Methods and the instrumentation are tightly coupled to this kind of measurement. Since all the relevant methods based on the usage of a classical theodolite equipped with one-axis magnetometer known as declination inclination magnetometer (DIM).
DIMs have several difficulties. Measurement process is carried out manually. Difficult to use DIM for I observation in equatorial region because the microscope cannot be read in nearly vertical position even with diagonal eyepiece. The computation of magnetic meridian is calculated by the operator during the measurements.
To overcome this problem at MinGeo company we developed a cable-less, digital, non-magnetic DIM instrument, named as FluxSet Declination Inclination Digital Station (DS), which was designed to facilitate the absolute magnetic measurements.
The aim of this presentation to asses the accuracy and precision of the absolute magnetic measurements, which were measured by some reference DIMs and DS instrument using null and this new proposed method.
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High Resolution Reflectivity Inversion with Cauchy Regularization and Acoustic Impedance Conversion
By H. KarslıSummaryAcoustic impedance (AI) is one of the most effective ways of quantitatively interpreting seismic data and can simply be obtained by converting the reflectivity series of the subsurface layers. Therefore, high resolution seismic reflectivity inversion (HRRI) of the seismic data has been an important step in the seismic data processing. However, when seismic data include noise, traditional damped and undumped least square inversion methods mostly lead to unreliable and low quality results. In addition, estimation of reflectivity from seismic data is generally band-limited and negatively affects impedance producing. For this reasons, in this study, I performed the HRRI with using Cauchy regularization (HRRI-CR). The method is iteratively applied to produce reflectivity with high resolution and has anti-noise ability, which leads to obtain accurate seismic acoustic impedance results. I tested the performance of the HRRI-CR method on synthetic data in obtaining the AI and showed that the method provides more accurate information about the layers when comparing the subsurface layer model with calculated impedance curves.
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Integrated Approach for Pre-drill Pore Pressure Prediction in Data-limited Exploration Area—A Case Study from Offshore Myanmar
SummaryIn Basement-high Area, Gulf of Moattama Basin, Myanmar, the geological setting is complex. A significant change in tectonostratigraphy setting across the area leads to different sedimentation and thermal maturation of the source rock, thereby highly variable subsurface pore pressure with undetermined mechanism occurred. Even though drillability of exploration wells depends crucially on a precise pore pressure prediction, the estimation of such pressure is problematic due to the lack of primary dataset. To ensure reliability, the assessment of pre-drill pore pressure and fracture gradient illustrated herein is performed by an integrated approach. Interval velocity from broadband seismic, borehole geophysical dataset, 3-D heat-flow model, and basin history analysis were taken into account during the course of the model construction. Additionally, to handle the prediction in this complicated geology setting, comprehensive geological interpretation was included and has shown the usefulness for validating the output and quantifying the sensible range of uncertainty.
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Velocity model building — key issue for seismic migration process
By M. GrigorovaSummaryPrestack Kirchhoff Time Migration (PSTM) is probably the most used method for obtaining proper image of complex subsurface. In areas of rapid lateral and vertical velocity changes, energy is dispersed in such a way that it is very complicated to be provide desired resolution of the data. The PSTM focuses scattered energy by moving it to a proper subsurface position if accurate velocity model is provided for migration. Only when energy is properly focused, stacking improves the quality of signals and eliminates noise. Building such velocity model, can bring significant improvement of seismic data quality (both resolution and continuity) and proper spatial structural positioning. For these reasons, velocity estimation process has great influence in seismic imaging. The process of moving seismic events to their actual location of occurrence in the subsurface is strongly dependant on the velocity model, but also is greatly affected of the whole processing quality. Seismic processing is long and comprehensive process of converting seismic field data into a meaningful seismic section and involves a lot of steps of data manipulations. The result is a high quality time image of the subsurface which better matches to the real geologic structures.
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Geophone array vs single sensor field data case study in Pannonian Basin
Authors M. Vanić, A. Saprygin, S. Milojević, I. Bogatyrev and A. PolivakhoSummaryAim of the research was to examine influence of single sensor interval and application of single sensor vs geophone array on 2D seismic data quality. Seismic data were acquired at two 2D lines with different sensor configuration. Line 1 was acquired with single sensor on 25m separation between sensors and with geophone linear array. Line 2 was acquired with single sensor at 12,5m spacing from which we obtained two data sets: with 12,5m single sensor spacing and with 25m single sensor spacing. All data sets were processed in a same way, with optimal parameters for each data set. Geophone array is giving us better coherency of reflections on stack section, leading to more geological details we can interpret. With geophone array ground roll is suppressed on later times, giving us better resolution and higher dominant frequencies in deeper parts. With 12,5 m useful signal is better preserved and it’s not spatial aliased. Ground roll is more efficiently removed on 12,5 m interval then on 25 m. Recommendation for future surveys with single sensor is to further decrease interval between sensors. This will also lead to better removal of ground roll and preserve more geological information for structural and quantitative interpretation.
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Crosshole seismic tomography for the detection of abandoned underground lignite mine galleries
Authors G. Kritikakis, A. Vafidis, G. Tsilfidis and K. PapakonstantinouSummaryThis work presents the results of crosshole seismic tomography geophysical survey at selected positions along the extension of Athens subway line #2, Ilion-Anthoupolis area (Greece). This geophysical survey aimed at: 1) the detection of abandoned underground lignite mine galleries at selected positions along subway line, 2) the mapping of geological formations and possible faults at the studied sites and 3) providing information for optimal design of tunnel path. Eleven (11) seismic tomograms of 225.3m total length and 520m total depth were generated between twenty (20) boreholes. The borehole source BIS-SH was utilized to produce highly repeatable compressional (P) waves at 2 m intervals and a hydrophone streamer consisted of 12 receivers at 1 meter intervals and a 12-channel seismograph were employed for seismic wave recording. First arrivals picking and travel time tomography were performed using SeisImager2D and ReflexW, respectively. Low velocity anomalies were found at 2 seismic sections, which probably are associated with abandoned underground lignite mine galleries or intact lignite layers. Moreover, indications for an unmapped fault presence revealed and a new tunnel path was proposed in order to avoid crossing the fault zone.
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Seismic investigation for the detection of liquefaction phenomena in an archaeological site, Lechaion, Greece
Authors G. Apostolopoulos, K. Leontarakis, C. Orfanos and D. Minos-MinopoulosSummaryLiquefaction phenomenon created destruction on the marble floor of an Early Christian Basilica at the area of ancient Lechaion port. This phenomenon is dominated in loose, of various grain size, sediments with water playing a key role. That gives great privilege to electromagnetic and geoelectrical methods to detect and discriminate liquefaction zones. Seismic methods though can detect loose sediment layers prone to liquefaction, as well as discriminate areas in relation with compaction after liquefaction phenomenon. The use of MASW method along with seismic refraction and 2D seismic sections with P and S velocities look promising in detecting liquefaction features.
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Establishing the necessary conditions of geopotential data for optimal use of the iterative 3D modelling software
Authors L. Asimopolos and N. AsimopolosSummaryFor understanding of complex geological phenomena, we can use 3D modelling software, based on the whole of knowledge and available data for the study area. The input data in this software include: digital terrain models, geological and geophysical maps, sections, drill-holes and geological interpretation, for assemble together into the same 3D space data from various sources, in order to ensure geometrical coherence. Are important to take into account the geology ‘boundary’ data (geology contacts, interfaces and limits), the deep geology and processing/filtering of geophysical data with properly algorithms. The type of filtering of gravimetric and magnetic data must be chosen based on the depth of the model we want to get. This is necessary because the values of the geophysical parameters recorded at the surface of the terrain contain weighted average information from both the surface and from different depths, even to the base of the Lithosphere.
In our paper we show algorithms for filtering data in 2D and 3D and example for a case study.
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Boundary Analysis Using Moving Average Differences of Bouguer Gravity Anomalies
Authors N.G. Aydin and T. IssevenSummaryBoundary analyses are commonly used methods in gravity data processing in order to investigate possible source body boundaries from Bouguer gravity anomalies. Despite most of the methods use derivatives to estimate boundaries, it is possible to apply boundary analysis using simple arithmetic operations. In this study, we present Moving Average Differences as a new and simple boundary analysis method. The method examines the smoothed areas of Bouguer anomalies by moving average filter to enhance the boundaries. We tested this method on artificial and actual Bouguer gravity anomalies and compared with commonly used boundary analysis methods.
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Nonlinear Analysis of Geomagnetic Variations Data from Panagyuriste Geomagnetic Observatory, Bulgaria
Authors M. Chamati and E. BotevSummaryWe apply the detrended fluctuation analysis (DFA) to the geomagnetic field data set collected from 14 till 31 May 2016 by the equipment at Panagyuriste Observatory, Bulgaria and calculate DFA exponent and its temporal evolution in different time scales (10-180 s, 10-900 s). Performing this analysis we obtain useful information about long range correlations of time series and about the global and the local variations of the geomagnetic field in the ULF range. It is found that an unusual behavior of the DFA exponent is observed only for the vertical (Z) geomagnetic component on 19.05.2016. We assume that this unusual behaviors of the scaling exponent and the fluctuation function in time scale 10-900 s may be due to lithospheric source.
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Regional mapping of geophysical and geological data in the process of their integrated analysis and interpretation
Authors P. Stavrev, S. Dimovski, A. Kisyov, P. Trifonova and M. MetodievSummaryA joint mapping of two type of data - geophysical gravity data in terms of Total Horizontal Gradient (THG) and geological data for the distribution of known metal ore deposits, occurrences and mineralization in Bulgaria, is presented in a regional scale. For the purpose the whole territory of Bulgaria is divided in 1270 areal elements E of size 10×10 km. The number V1 of metal ore objects, and the length V2 (km) of gravity lineaments (THG, mGal/km), that appear in every single element E, are used as input data. Thus, a space index of coincidence, Qi = [(V1+V2)/√(V1 2+V2 2+C)]i, can be calculated in the areal elements Ei, i=1,2, …, N. The space distribution of this index gives us the integrated geological-geophysical information which can be used for revealing of different characteristics such as common origin, similar tectonic environment, etc.
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Gravity networks for the Geodetic Reference Framework of Albania
Authors H. Reci, A. Stampolidis, N. Perparim, G. Tsokas, S. Bushati, R. Pašteka and K. QirkoSummaryThis paper presents a general overview of gravimetric measurements carried out for the first order gravimetric network of Albania. Data compensation, correction methodologies, interpretation and related results have been presented as well. Relative gravimetric measurements were carried out in 42points, with two CG-5 instruments. Real Vertical Gradients have been measured at all the points of first order network which together with other corrections, are used in the final data compensation in order to bring the final values at reference point as absolute ones. The measurements were carried out during the period from August to October 2018, in collaboration with Aristotle University of Thessaloniki, Department of Geophysics. The project was supported by the Agency of Geospatial Information of Albania.
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Seawater intrusion in the Alepu protected area, part of the Ropotamo complex (Southern Bulgaria)
Authors N. Stoyanov, S. Dimovski and A. KisyovSummaryThe article presents the main results from a complex study of the processes of seawater intrusion in a costal aquifer and the subsequent changes in composition and qualities of surface waters and groundwater in a wetland of international importance (a Ramsar Site). With purpose of preliminary assessment of the spatial boundaries and salinity level of the coastal aquifer complex, limited geoelectrical studies were carried out in the area. The obtained electrical resistivity sections along all studied lines are transformed into hydrogeological models of saline water intrusion through key criteria.
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Influence of geomagnetic activity on electron concentration of the ionosphere
By R. BojilovaSummaryThe present study investigates the seasonal dependence of the geomagnetic activity influence on the diurnal variability of the maximum electron concentration of the ionosphere over Bulgaria. Data from the ionosonde station Sofia for the period of 1995–2014 are used. The geomagnetic activity is described by the planetary Kp-index. The ionospheric response to the geomagnetic storms is studied by considering the deviation of the diurnal variability from its steady (median) course. It is found that the ionospheric reaction in summer is stronger than that in winter. Using the correlation analysis the seasonal dependence of the ionospheric response time delay for two ionospheric characteristics, foF2 and MUF3000, was determined. It is found that the time delay of the negative ionoispheric response in winter is longer than that in summer; an explanation of this result is offered.
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Indexing of ULF/ELF electromagnetic emissions as a health and life quality factor
Authors D. Teodosiev, P. Nenovski, M. Chamati, D. Borisova and T. NikolovaSummaryThe authors of the presented work aim to present a project for future work in the field of electromagnetic geophysical methods for applying ULF/ELF electromagnetic emissions measurements as a health and life quality factor.
The sources of ULF and ELF are various and could be classified as outer and internal in respect the place of generation. The outer, generally, are geomagnetic pulsations, the Schuman resonance, thunderbird activities having at all global character. The outer sources are due to natural magneto telluric currents generated in globe core, or a product of artificial radar work of humans reaching tens of MW of power. The level of ULF and ELF variations is an important parameter that directly influences the live cells metabolism.
The expected results are:
Development of indexing methodology of the ULF/ELF variation
Comparison between the traditional indexations and the proposed one
Elaboration of a practical evaluation scale having direct impact on the human’s health and the live quality
Development of a measuring system for extending existing one
Informing the public with adequate information as a media announces, workshop etc. about the nature, the benefits and the level of damage caused by these radiation, especially of the ULF/ELF diapason.
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Site characterization using integrated well logging techniques: Preliminary results for hydraulic and geometrical evaluation
More LessSummaryGroundwater flow is mainly dominated by fractures or secondary porosity especially in rock formation considering that rocks generally have very low porosity and permeability. The key issue is thereby to identify fractures and characterize their role in groundwater flow. A dedicated test-bed was established and managed to improve field testing techniques and analysis methods for characterizing flow and transport properties of formations. This article paid attention to the hydrogeophysical characterization of test-bed site, and furthermore focused on the identification of individual fracture attributes and high permeability conduits through the thinly layered and fractured zone using comprehensive integrated interpretation based on borehole and core data. Gamma ray logs gave us an information to lithologic characteristics of test-bed, and spectral gamma ray signature assisted in the evaluation of lithology variations and interval stratigraphy. Temperature and borehole image analysis yielded significant identification of all fractures in which active groundwater flow occurs. Understanding fractured formation properties such as lithology, fracture distribution, aperture, and fracture development led to conceptual model reflecting hydraulically active fractures. Ongoing research focuses on the hydraulic and geometrical characterization of fracture networks as well as individual fractures.
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Aperture width estimation from acoustic televiewer log using 3 inches physical fractured borehole model
More LessSummaryBorehole image logging has been used in various fields by measuring the dip and strike characteristics of the fractures. In this study, we conducted an experiment on the fractured borehole model to understand the possibility of estimating the aperture width using ATV data. We used ATV tool from Mount Sopris in the US and Robertson Geologging in the UK. The diameter of the borehole model is 3 inches, the dip angle are 0, 30, 60, and 90, respectively, and the aperture width are 1, 2, 3, and 5 mm, respectively. To investigate the relationship between the fracture borehole model and the ATV measured data, the amplitude and the travel-time data were carefully analysed. As a result of the test, in case of the dip angle is 0, the aperture width should be at least 3 mm. As the dip angle increases from 30 to 60 degrees, the aperture width can be more easily distinguished, but it tends to be measured larger than the actual. When the dip angle is 90 degrees, it is possible to distinguish the 2 mm aperture width. It is recommended that amplitude data be used rather than observational data when estimating aperture width
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Monitoring of landslide processes at the NE Bulgaria by joint use of GNSS and InSAR
Authors M. Atanasova-Zlatareva, H. Nikolov, I. Georgiev, A. Ivanov and N. DimitrovSummaryThe objective of the newly started project is monitoring the ongoing landslide processes. This will be achieved by using of an innovative methodology for continuous monitoring of landslide areas by integrating interferometric images and GNSS data from permanent and local geodetic networks. The study will give reliable data for ongoing risky geo-processes for the region of the Northeastern Bulgaria, known with several large active landslides. These results are important for understanding the origin and dynamics of landslide processes as well as assessing the resulting hazards. Local archive with Sentinel-1A/B images for this region is created and interferograms are produced.
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Impact of atmospheric refraction on precise leveling observations
Authors N. Dimitrov, P. Danchev and I. GeorgievSummaryThe effect of atmospheric refraction on the results of precise leveling measurements is investigated. This study is based on level measurements for 30 km line provided by Geodesy, Cartography and Cadastre Agency. The results show that refraction’s impact is not eliminated with one and the same positive and negative differences of elevation. The correction must be applied for each instrument set-up. Largest values of refraction are observed in the leveling distances with highest terrain slope. The error caused by refraction is a significant systematic error in the leveling measurements and it is mandatory to be applied.
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DInSAR in displacement detection after seismic events
Authors M. Atanasova, H. Nikolov and V. ProtopopovaSummaryEarthquakes have devastating effect on population, landscape and economy. Since it is quite challenging to predict those events of utmost importance is to obtain reliable information after they had happened. This information is essential for rescue operations and for preparation of post-event management plans. In this paper two earthquake events are studied and produced are the ground displacement maps have been produced. Those maps are created on the basis of interferometric images obtained after processing SAR data from the ESA Sentinel-1 mission. The results have been compared with in-situ observations and measurements made after the event exhibiting good correlation with them.
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Remote sensing of land covers over a test area
Authors D. Borisova, M. Goranova and V. HristovaSummaryRemote sensing methods as a part of geophysics have wide applications in different areas of science and practice. In the presented work the team of PhD students and Post-docs aim to collect spectral data for filling in thematic database. The spectral data are result of performed laboratory and terrain spectrometric measurements of the presented in a test area land covers (minerals, rocks, etc.). The result of the project work is collection of remote sensing data and additional information for filling in thematic spectral database in remote sensing monitoring of land covers in Novi Iskar region, Sofia, Bulgaria. Therefore the results will increase efficiency of research investigations in remote sensing monitoring of land covers, synergy between different fields of science and practice, and shared information between researchers.
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Relations between lower stratospheric O3 and ENSO
Authors T. Velichkova and N. KilifarskaSummaryIt is well accepted that temperature difference between western and eastern equatorial Pacific is the main driver of ENSO climate mode. The temporal variability of the spatial distribution of this difference, on the other hand, corresponds to the different ENSO phases – El Nino and La Nina. Although the rough periodicity of ENSO events is well known, it possesses also long-term variability, the reason(s) for which is unknown.
This study offers an explanation of the ENSO variations, related to the lower stratospheric ozone and its control over the near tropopause temperature and humidity. Statistical analysis of the spatial distribution of connectivity between ozone and Nino3.4 index reveal strong coherence in their temporal variations, with the leading role of ozone. Additional analysis of the coupling between ozone at 70 hPa and water vapour at 150 hPa confirms the proposed mechanism for ozone influence on the near the tropopause water vapour and consequently on the regional pattern of surface temperature.
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Paleomagnetic investigation of the Miocene - Quaternary volcanic rocks between Varto-Tunceli
More LessSummaryAfter collision between the Arabian and the Eurasian plates, Anatolian plate began to move westward, along the East Anatolian Fault Zone (EAFZ) and North Anatolian Fault Zone (NAFZ). NAFZ and EAFZ meet with the Varto Fault Zone (VFZ) and form a triple junction in the 10 km northeast of Karlıova. In order to determine the tectonic evolution of Karlıova Triple Junction (KTJ) and it’s around, paleomagnetic samples were collected from the volcanic rocks, whose ages range from Miocene to Quaternary times. Our paleomagnetic results, obtained from the Karlıova - Varto - Solhan region are indicate that there are counterclockwise (CCW) rotation in the regions closer to the NAFZ and EAFZ. different rotations are seen in the east of the KTJ, both western and eastern parts of the Varto Fault Zone. Also there is a remarkable change in the tectonic regime of the Tunceli - Elazığ province in the Miocene - Pleistocene time interval.
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Lithofacies identification using anisotropic parameters from logging data:A case study on Muglad Basin, South Sudan
More LessSummaryThe formation identification of reservoirs using seismic reflection data and log data for anisotropic reservoirs has tendencies in differences to the true formation. Considering on the anisotropic parameters is the one of methods for reducing this difference. For the reservoir formation discrimination of lithofacies, surface geological survey, geophysical exploration, drill core, and log data are analysed. In this study we tried to find out anisotropic parameters from log data using Backus averaging, then applied it to lithofacies discrimination. We calculated Lame’s constant and shear modulus from the log data in the Muglad Basin. After applying Backus averaging to these, we obtained the stiffness coefficients then calculated the anisotropic parameters. The lithofacies for reservoirs were classified by 11 layers based on the anisotropic parameters. If there is no drill core data or drilling-cuttings, the anisotropic parameters from log data is efficient for lithofacies discrimination. The classification of sedimentary layers without drill core or drill-cuttings, this approach will be useful for discrimination of lithofacies using anisotropic parameters from Vp, Vs and density log.
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Teleseismic Receiver Functions and Gutenberg-Richter b-value distributions around the Lake Van region (eastern Turkey)
More LessSummaryThis study will supply an overview of crust and upper mantle structure beneath the Lake Van region based on the Receiver Function analyses of P- and S- waves using the teleseismic data set taken from the European Integrated Data Archive. All inversion results will depict the present day tectonics of the Lake Van region. Also, spatial variations of the b-values are calculated by using data covers all earthquakes occurred between 1900-2017. The b-values will inform us about the compatibility between the seismic regime and seismic velocity for the depth from near surface to 30 km.
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Thrusting tectonic and the oil traps formation in the Albania Ionian tectonic zone
By A. MesonjesiSummaryMany studies have described the complicated tectonic pattern of Albanides. The data show the presence of the three lithological formations: evaporitic, carbonate and clastic formations. This paper presents the tectonic model created as a result of the relationships of these formations with each other. The older formation, evaporitic formation, is already accepted to have acted as a detachment layer, which is also cut by thrusts that carry evaporites to the surface along their hanging walls.
This paper attempts also to show the relationship of this tectonic pattern with the oil fields discovered to date in Albania.
Many published papers show different examples about the complicated tectonic model with a lot of westword thrusting tectonic within Ionian zone in Albania, while the authors of this paper are refering to Kurveleshi area as an example.
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Empirical relations converting seismic intensity to moment magnitude
Authors I. Aleksandrova, D. Solakov, S. Simeonova and P. RaykovaSummaryIntensity is a basic parameter for assessment historical seismicity - realized until the instrumental period. The relation between intensity and seismic moment magnitude allows the creation of a homogeneous catalog. The homogeneous catalog provides compatibility of the input seismological data and allow reliable estimation of the energy distribution of earthquakes - an important stage in seismological research and essential for seismic hazard assessment. In this study are analyzed 92 earthquakes with magnitude above 4.0 (M>4.0), which occurred in space window 37.0° – 45.0° N; 21.0° – 30.0° E, during the time period 1912 – 2018 and the coefficients of the linear regression MW=MW(I0/Imax) are evaluated.
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The april 2017 MS5.2 kurbneshi earthquake and its seismogenic zone
More LessSummaryOn 8 April 2017 (GMT 13:53) a moderate Ms5.2 earthquake sequence burst in the Kurbnesh-Skavica tectonic fault zone. The main shock was located 3 km in north of Kurbnesh town and 54 km NNE of Tirana city and was felt over a larger area from northen to southen Albania. The Kurbnesh-Skavica tectonic fault zone is exposed on the ground at a length of about 35 km, according to the SW-NE direction. This tectonic segment is part of Ulza-Kurbnesh-Kukes-Prizren seismogenic fault zone. For this analysis, the local and regional data concerning the epicentral locations, focal mechanisms, macroseismic data of the April 2017 earthquake were used. The focal mechanisms of the mainshocks, indicate that deformation is taken up by NE-SW trending normal faults with strike-slip elements. Analysis of this earthquake and some other recently moderate earthquakes and also of seismic activity shed light on the seismotectonics of the area and the stress field. The Kurbnesh-Skavica transversal fault zone presents a threat to the nearby urban areas.
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Frictional Strength of Faults: Evidence for Post Seismic Deformation
By A. PinarSummaryFrictional coefficient of faults is investigated using the approach described in Iio (1997) where the orientation of a fault plane relative to the maximum compression direction is related through the equation β = 1/2 arctan (1/μ), where β is the angle between the direction of the maximum compression and the fault plane orientation, and μ is coefficient of friction. The data used are the frequency distribution of azimuth and plunges of P- and T-axes of focal mechanisms. The relation between β and μ is illustrated for different types of faults. Aftershocks of 2011 Lake Van earthquake (Mw=7.2) are utilized to demonstrate the technique. Focal mechanisms for about 400 aftershocks (Mw>3.5) are retrieved showing mostly reverse and strike-slip faulting mechanisms. The frequency distribution of P-axis azimuths of the mechanisms are utilized as an approach to investigate the frictional strength of faults on and around the ruptured fault. The azimuth of predominant frequency of P-axis distribution determined separately for reverse and strike-slip focal mechanism are close to the orientation of the maximum compressive stress axis pointing out low frictional coefficients that is likely due to post-seismic deformation.
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Seismicity of the Shabla-Kaliakra-Balchik region over the period 1986–2014
Authors M. Tsekov, E. Botev, L. Dimova and R. RaykovaSummaryWe study spatial and temporal properties of the seismic activity in the Shabla-Kavarna-Balchik region over the period 1986–2014. This region is located in the NE part of Bulgaria (longitude range between 27.75E and 30.0E, and latitude range between 43.0N and 44.3N). The seismic activity there is related to a multitude of onshore and offshore faults. We use data from the Bulgarian National Seismic Network to identify 204 earthquakes in the region for the considered period. We find that the seismic activity rate increases abruptly after the August 5th 2009 Md=4.7 offshore earthquake. We identify the most active faults in the region for the considered period: (1) the Kaliakra fault; (2) the Batovo fault; (3) the Shabla fault; (4) the Razelm fault, as well as several near-coastal NNE-SSW faults where the aftershocks of the strong quake of August 2009 concentrated. The spatiotemporal behviour of the earthquake activity in the region suggests possible interaction between adjacent or intersecting regional faults.
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Extensive strike-slip faulting to NNW-part of Lake Erçek region by finite source and coulomb modeling (E-Anatolia)
More LessSummaryWe have examined the finite fault source characteristics of the October 23, 2011 Erciş-Van earthquake through modelling the seismic waveforms recorded at local and teleseismc distances. A finite source model has been retrieved using the teleseismic body waveforms constraining the source location by info given in previous studies. The finite source modeling suggests a major moment release on a transpressive fault segment located at the central part of the source region surrounded to the SW and NE by strike-slip faults acting as tear faults with the accretionary prism in Eastern Anatolia. We examine the fault interaction between the fault ruptured by the mainshock and the faults that have been activated by the mainshock. Tremendous strike-slip faulting has been observed to the NE of the source region extending in a depth range from shallow subsurface to the lower crust. A Coulomb stress modeling using the slip model derived indicates a stress increase in the lower crust on the optimally oriented strike-slip faults extending from shallow crust to deeper lower crust.
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The present geodynamics and kinematics of albanides
More LessSummaryIn the present work, an introductive summary of the Albanian geological position within the framework of the regional geology is briefly given. Additionally, the neotectonic structure of the Albanian territory is comprehensively described, analyzing the geological formations which build it up. The geological structure of Albania appears folded and complicated by various tectonic faults of different type and age.
Treatment from the regional geological standpoint is ascribed to the relationship between the Albanian orogens and the Adria microplate, as a reference tectonic unit, continuously playing an important role in the geodynamics, kinematics and tectonic modeling of the Mediterranean basin, and consequently on the Albanian territory.
Herein, results on the Albanian territory geodynamics and its relation to the Apulian block and Eurasia are discussed referring to the GPS data obtained from the Albanian GNSS and neighboring analog networks. Special attention is dedicated to the correlation of these data with the tectonic pattern of the Albanian territory. Based on the instrumental observations, the movements and the strain pattern of the external and internal Albanides, referred to the up-mentioned tectonic blocs, are correspondingly discussed.
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Azimuthal rotation-dependent spatial distributional patterns of small repeaters estimated from microseismic data-set of Gokova Gulf (SW-Turkey)
By M. TokerSummarySmall repeating earthquakes reveal properties such as the temporal and spatial clustering of events, which serve as a key tool to constrain the rate/state stress transfer and seismogenetic properties of active seismic areas. In our case, azimuthal rotation-dependent spatial patterns of the small repeaters were estimated from the four years-microseismic data set (∼10.000 events) of Gokova Gulf (GG) (SW-Turkey). The process of microseismicity taking place in Gokova Gulf in 2010–2014 was relocated in an attempt to quantify the prominent seismogeneity in the GG and to unveil properties of the associated current stress state of the GG and its projected surroundings at crustal depths. In the present study, we evaluated the 26th November 2012 Bozburun mainshock (Mw 4.4, 4.8) with its accompanying small repeating events and its accompanying multiple aftershock series; the 16th May 2013 Ula aftershock (Mw 4.6), the 25th March 2014 Bozburun aftershock (Mw 4.0), the 1th May 2014 Bodrum aftershock (Mw 4.0) with their accompanying small repeating events, symptomatically occurring in the Bozburun, Ula, and Bodrum areas of the GG by using the microseismic data set. Then, we produced azimuth-dependent, rotational and cross sectional distributional patterns of all microearthquake clusters at depth, up to ∼ 160 km.
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Unipolar Magnetic Pulses – A Manifestation of Stress Induced Impulse Modes (A Petroplasma Viewpoint)
By P. NenovskiSummaryUnipolar magnetic pulses (UMPs) are recorded prior to strong earthquakes at different points: California, Italy, Peru. Their basic characteristics are considered and analyzed. Supposed mechanism of UMPs are underground electric currents of impulse type. Laboratory experiments have evidenced the phenomenon that igneous rocks under stress/strain change conditions turn into semiconductor plasma. Stress induced (current-carrying) impulse modes of rock plasma (petroplasma) are suggested. The emerging diffusion processes inside and outside the current-carrying channel are discussed to explain the pre-seismic UMPs ⌝ their appearance, with one polarity, pulse width, etc. A possible cause of pre-seismic UMPs is proposed.
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Pre-earthquake changes of atmospheric ozone and temperature over the wide Balkan region
More LessSummaryIncreased long-wave thermal emissions is found out prior to many strong earthquakes. Within the wide Balkans, however, there are a few recent strong earthquakes (EQs), so our analysis is aimed to test the hypothesis for the pre-EQ generation of near surface thermal anomalies, for EQs with magnitude 4 or greater. 1872 events have been selected from the EMSC catalogue of earthquakes, occurred in magnetically quiet periods, during the time interval 2004–2014. The selected area for investigations covers the region with coordinates: 80–300E longitude and 350–530N latitude. Besides temperature, the near tropopause ozone and water vapour are also analysed.
Statistical analyses, based on the ANOVA F-test of variances, and the t-test of mean values, reveals that the suggested pre-EQ influence of the tectonic processes is stronger and most significant on the near tropopause ozone density. This influence is still traceable in the air temperature at 2m above the surface, and notably reduced in the soil temperature at ~3m beneath the surface. This result is suggestive that the pre-EQ anomalies in the lower stratospheric ozone density are projected on the surface temperature, due to modulation of the upper tropospheric water vapour greenhouse power.
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GMPEs used in seismic hazard assessment for Bulgaria-selection and testing in Bulgaria
Authors D.E. Solakov, S. Simeonova, P. Raykova, E. Oynakov and I. AleksandrovaSummaryGround Motion Prediction Equations-GMPEs define the values of a ground motion parameter as a function of earthquake size and the distance in terms of both expected values and their dispersion. GMPEs are essential in probabilistic seismic hazard studies, which are a key step for the evaluation of seismic risk and loss estimation for a region. In the present study, six attenuation relationships were selected for shallow and three for intermediate depth earthquakes on the base of general criteria. The Nakamura method was applied to classify the soil conditions of Bulgarian stations. The LLH and LH approaches were used for quantifying the goodness of fit of these relations to a large dataset of ground motion data from Balkan region.
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Population exposure index – an element of seismic risk assessment
Authors D. Solakov, M. Metodiev, S. Simeonova and P. TrifonovaSummaryThis paper presents assessment of one of the main elements of the seismic risk – human exposure at the territory of Bulgaria. Seismic hazard in terms of Peak Ground Acceleration map is modelled using GIS and overlaid with a model of population distribution in order to extract a population exposure index (PEI). We use as indicator the population density to allow comparison between less populated and more populated regions. Analysis is performed on a gridded network with a single element of 1×1 kilometer. Information about the population cover the period 2011–2018 using data from the last census performed in 2011 and the updated information for the towns provided by the National Statistical Institute for 2018. As a result, a classification of region is provided based on the results obtained for PEI.
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Relief resolution effect on the tsunami numerical modelling
Authors L. Dimova and R. RaykovaSummaryThe relief resolution effect on the tsunami numerical modelling was evaluated in this study. One hypothetical tsunamigenic source with earthquake magnitude 7.5 was modelled in the area of the Shabla-Kaliakra seismic zone in the northeastern Bulgarian Black Sea coast. The resolution of computational grids on which the numerical simulations were made are 50 m, 250 m and 500 m. Synthetic mareograms were calculated at a number of points near the coastline and the results obtained by different grids, were compared. The vertical water column on the coastline generated by the modelled event is evaluated, indicating that higher resolution in the finer grid leads to more realistic results. Radiation pattern of the tsunami waves has insignificant changes using relief grids with different steps. In general the extreme amplitudes of the modelled tsunami vary with different relief resolution. The phase shift in the wave trains is more significant for a specific location that causes important changes in the estimation of vertical water column on the shore at this point. Further that it is a basis of over or underestimation of the local tsunami hazard.
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Ice generated events in Perunika Glacier, recorded by LIVV station
Authors G. Georgieva, L. Dimitrova and V. GourevSummaryIn this paper we present the initial results from our study of the seismicity generated by the processes in the Perunika glacier, Livingston Island, Antarctica recorded from Bulgarian broad band seismic station LIVV and its relationship with measured GNSS displacements on the glacier surface. Seismic and GNSS data from January 2018 were used. Different types of ice-generated events were observed. About 90 events with identical waveforms, very short duration (up to 1–2 s) and clear P and S onset were localized. GNSS measurements were carried out in five points on glacier and later the velocity in cm/day was computed.
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Evaluation of geophysical methods for studying snowfields in Pirin Mountain, Bulgaria
Authors G. Georgieva, A. Kisyov, C. Tzankov, B. Chtirkova, V. Gourev and Y. IvanovSummaryThe article stages the results of surveys conducted in 2018 in the Pirin Mountain in order to evaluate geophysical methods for studying glacier thickness and structure. Two perennial snowfields are known in Pirin and the test investigations were carried out on one of them, situated in the area of Golyam Kazan. Ground penetrating radar (GPR) and 2D electrical resistivity tomography (ERT) were selected for the survey.
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Marine (Sonar and Shallowe Seismic) Investigations in Izmir Gulf-New Results
By M. SenozSummaryİzmir Gulf is an actively growing shallow marine basin controlled by active faults trending NE, NW, N–S and E–W in the West Anatolian Extensional Province. The bay is topographically divided into an E–W-trending inner bay and a NW-trending outer bay. In the bathymetric maps was the gulf according to the shoreline into three regions divided. These regions are:the eastern (inner) part, the central part (outer part) and the western part Geologicaly is the the inner bay of İzmir an asymmetric graben structure containing upper cretaceous–Palaeocene basement, an older succession of lower to upper Miocene basin fill, overlain with angular unconformity by a younger Plio–Quaternary basin fill. The older succession contain a thick, folded and coal-bearing continental volcano-sedimentary sequence. The younger succession includes the upper Pliocene–Pleistocene Görece formation and Holocene to recent alluvial fan, fan delta to shallow marine deposits.This shallowe marine deposites will be investigated today systematicaly using modern shallowe marine geophysical instruments. This investigations reveals everyday more features of the sea bottom related bathymetry (topographie,), structures on the sea bottom (geothermal site, naturell gas site, gas seeps site, mud volcanouse site, pockmark-pockmark field site and man made object site (wreck site) in the regions of İzmir bay.
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Single spectrum analysis for monthly sea level data from Varna tide gauge station
Authors A. Ivanov, I. Georgiev and N. DimitrovSummaryClimate changes and global warming are assumed for main reasons of constant sea level rise. Survey methods such as altimetric measurements are essential for determining global processes related to sea level change, but the regional and local changes are also important. In this paper regional sea level changes at tide gauge station Varna at Black sea coast is analyzed. Single spectrum analysis is carried out for monthly sea level data for period 1929–2019. The sea level trend, long term tidal constituents, amplitudes and phases are estimated. The results clearly indicates positive mean sea level trend with value of 1.2 ±0.1mm/yr.
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Digital terrain model of the seafloor of south bulgarian black sea coast
Authors T. Lambev and B. ProdanovSummaryThe paper discuss the creation of a composite seafloor digital terrain model of the south Bulgarian Black Sea coast - broad Burgas Bay from Cape Emine to Cape Maslen nos. It is a result of processing and assembling data from single beam echosounder and multibeam sonar systems derived from the Institute of Oceanology-BAS, bathymetric LiDAR data and data from digitizing water lines from marine navigational charts. Data from single beam echosounder and multibeam sonar systems were acquired during the implementation of various national and international projects of IO-BAS. Areas where no data are available were completed by manually drown isobaths built on the grounds of the surrounding terrain and circular interpolation with step of 55 meters. By combining all the data a comprehensive 3D digital terrain model of the topography of the seafloor with resolution of 1/128 arc minute or cell size of 14 meters was created. The digital terrain model allows detailed understanding of the seafloor morphology and successfully can be used in the compilation of highly accurate, navigational charts. The work is a result of the implementation of a project under the Program for supporting young scientists and PhD students at the Bulgarian Academy of Sciences.
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Is it possible to obtain reliable archaeomagnetic results from baked clays with very weak magnetism?
Authors M. Avramova-Kostadinova and P. DimitrovSummaryThe primary goal of archaeomagnetism is to accumulate information about the behaviour of the local geomagnetic field in the past using well-dated archaeological baked clay materials. Sometimes, however, these materials can possess weak magnetic properties due to an insufficient firing in the antiquity, low amount of ferro-oxides or domination of antiferromagnetic minerals. In such cases, it is not possible applying the complete set of laboratory experiments and requirements, which assure the authenticity of archaeomagnetic data.
A detailed investigation of samples with extremely weak magnetism was performed and the reliability of the obtained data is demonstrated. These results cannot be included in archaeomagnetic database as referent feature because they will not pass all the necessary quality criteria. However, the produced archaeomagnetic determinations can serve as valuable check-up of the calculated secular variation curves (when the structure studied is well archaeologically constrained) or can be used for archaeomagnetic dating.
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Applying archaeomagnetic method to identify the purpose of usage of archaeological furnaces
Authors P. Dimitrov and M. Kostadinova-AvramovaSummaryThe potential of archaeomagnetism as a reliable dating tool (absolute and relative) is beyond any doubt. Magnetism of archaeological baked clays, however, can be used for solving other archaeological problems that are not related to the site’s chronology. In some cases, the discovered archaeological structures are so fragmented and poorly preserved that it is very difficult to establish the purpose of their usage. In this study, magnetic measurements were applied to determine maximum firing temperatures for several structures found at Prehistoric Settlement Damyanitza to find out if they were used for domestic purposes or for ceramic production. The determined firing temperatures with one exception vary from 730 to 770 °C and they are very similar to these observed for Neolithic and Eneolithic ceramic fragments analyzed with thermomagnetic method. Consequently, it can be concluded that the ovens from Damyanitza were used in the past for pottery production.
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Geophysical investigation of hidden wall passages in the historical building of Hungarian Academy of Sciences
Authors G.A. Hutka, P. Nagy, Z. Prónay and E. TörösSummaryThe main building of the Hungarian Academy of Sciences is a neo-Renaissance palace built in 1865 in Budapest, situated on the eastern bank of the Danube River. In October 2018 MinGeo Ltd. was entrusted with the task of the inspection of hidden wall passages and chimneys connected to the ceremonial hall of the Academy in order to improve its ventilation. For this purpose, we used ultra-high resolution GPR inside the building; endoscope camera and cable locator in the chimneys. With this method five wall passages were found on the ground floor of the ceremonial hall and seven on its gallery, while we had an indication of a passage at 8 locations in the Museum hall on the floor above. The GPR measurements also revealed 4 so far unknown passages in the southern wall of the ceremonial hall. With the opening of the outlet of these four passages the ventilation of the hall could easily be improved. If this is not enough, there are several more passages connected to the chimneys, which also could be utilized for this purpose.
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Civil and scientific applications using data from the International Monitoring System of the CTBTO
Authors C. Saragiotis, R. LeBras, P. Mialle and P. NielsenSummaryThe role of the CTBTO is to ensure that the Comprehensive Nuclear-Test Ban Treaty is observed by means of detecting nuclear tests. The data collected by its International Monitoring Station, however, can and have been used to contribute to sustainable development, knowledge expansion and human welfare. A number of such civil and scientific applications are be presented as well as vDEC, a system put in place by the CTBTO to share its data with interested parties.
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Virtual Seismological Network of Sofia University - a research database
Authors L. Dimova, R. Raykova, L. Dimitrova and M. TsekovSummaryVirtual Seismological Network of Sofia University (VSNSU) is operating since 2015 and it is supported by the Scientific Research Fund of Sofia University. The network consists of 16 seismic stations from 6 different countries in the Balkan Peninsula region. The seismological database consists of structured files containing: the characteristics of each analyzed earthquake (location, origin time, depth, etc.); different magnitudes; focal mechanisms; and seismic phases from the station records. The database structured a different measurements made since the operation of the VSNSU and included also the available information from different international datacenters. Database includes also the specific manuals for the used software explained by an individual example. The purpose of the established database is to simplify the education and research of the students as well as to contribute to the inter-institutional international cooperation.
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National Geoinformation Center – scientific infrastructure for dissemination of accurate, durable and reliable geodata and products
Authors N. Miloshev, P. Trifonova, I. Georgiev, T. Marinova, V. Slabakova, N. Dobrev, V. Milusheva and T. GuerovSummaryThe NATIONAL GEOINFORMATION CENTER (NGIC) is a newly established scientific infrastructure for cooperation and integration of human resources, informational products and data from monitoring networks and observatories, their complex analysis and implementation into services to the community. It is part of the National road map for scientific infrastructure (2017–2023), adopted by the Council of Ministers of Bulgaria. NGIC is a distributed infrastructure with national territorial coverage and incorporates monitoring networks, observatories, observation stations, laboratories, computing centers and other specialized equipment of the participating partners. The partners joined in the research consortium are four institutes working in the field of Earth observation: the National Institute of Geophysics, Geodesy and Geography (NIGGG), the National Institute of Meteorology and Hydrology (NIMH), the Institute of Oceanology (IO), the Geological Institute (GI), and two institutes competent in ICT: the Institute of Mathematics and Informatics (IMI) and the Institute of Information and Communication Technologies (ICT). Using all the initial capacity which partners have, NGIC will strive to provide permanent access to geo information, to deliver reliable data and services for the geo-environment and to support the effective prevention from natural and anthropogenic disasters and industrial accidents.
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Investigation of Trees’ Internal Structure Using Electric Resistivity Method
Authors Y. Yilmaz, T. Isseven and N.G. AydinSummaryThe resistivity method in geophysics is used to solve various geological and engineering problems. Recently, this non-destructive method has been used on trees to investigate possible infections within the trunks by creating resistivity tomography images. In this study, the electrical resistivity method has been applied on various tree types at three different locations in Istanbul, Turkey. Then the measured data are processed via a specifically written program in MATLAB. The processed data are used to prepare resistivity contour plots as slices and the results are interpreted considering moisture content within the trunk.
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