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6th Congress of the Balkan Geophysical Society
- Conference date: 03 Oct 2011 - 06 Oct 2011
- Location: Budapest, Hungary
- Published: 03 October 2011
61 - 80 of 158 results
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Comparative Gephysical and Mining Forensic Analysis in exploration of Building Damages in Area of Mine „Lipnica
Authors E.D. Delic, Z.K. Karadzin and E.H. HusejnagicGeophysical explorations enable determination of causes to damage or inflicted injuries, understanding of initiation mechanism of accident and proofing of hypothesis beyond reasonable doubt in court proceedings thus leading to material evidence that will either confirm or deny initial hypothesis. Mining operations in Lipnica underground mine were conducted for about 50 years and were stopped at the begging of the war in 1992. Main openings of the mine, as well as the former mining panels in roof coal seam, are located directly under the settlement Lipnica. After more than two decades of mine closure a number of court proceedings are still pending. It concerns claims for compensation of evident damages inflicted on houses. Conventional calculation methods of subsidence dynamics and time frame of consolidation process that were defined in planning of mining operations and previous forensic investigation were mainly stressing the fact that the giving time distance is to long to expect effects of mining operations. The paper gives overview of a comparative analysis of mining-geological conditions and geophysical explorations in the case of forensic investigation into damages inflicted of houses, including analysis of possibilities to apply geophysical forensics in investigation of underground mining operations impacts.
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Continuous Wavelet Transform – A Study in Enhancement of Signal Amplitude Spectra
More LessAnalytic transformations of complex signals provide new perspectives of the intrinsic properties of these observations. Continuous Wavelet Transform (CWT) permits spatial presentation of the frequency and amplitude properties of the signal. This specific feature of the method allows investigation of non-stationary signals, which is not possible with Fourier Transform. The signal enhancement process requires selection of a mother and subsequent daughter wavelets, which depend on the spectral conditions of the data of interest. Examples illustrate that CWT enhances the upper end of the frequencies of even vintage seismic reflections from the sedimentary basin environments. Distinct structural architecture of local tensional fractures zones, barely recognizable on the original data sets, are revealed by the implementation of CWT. Similar implementation of the technique to recent field data, from the same locality, significantly broadens the spectral band of the reflection waveforms improving both the vertical and horizontal resolution. Mapping of complex fractures are more detailed after CWT processing of records from crystalline basement environments.
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Mutiscale Analysis of 3D Analytic Signal using the 2D Continuous Wavelet Transform
Authors S. Ouadfeul and L. AliouaneIn this paper we have analyzed the aeromagnetic data using the 3D analytic signal technique combined with the 2D continuous wavelet transform (CWT). The objective is to delineate structural boundaries using the spatial distribution of maxima of modulus of the CWT of the analytic signal (AS). The proposed idea has been applied at the geomagnetic data of In Ouzzal area, it is located in the western of Hoggar(Algeria). Obtained results are compared with geological map and analytic signal solutions. It shows that with this approach we are able to resolve the problem of noise effect on the analytic signal solutions, and the reduction to the pole in the contacts identification by the CWT. Our method shows a good precision where geological contacts are known. Keywords: aeromagnetic data, analytic signal, boundaries, CWT, maxima.
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Near-surface Earth Parameter Estimation via Recompressive Filtering
Authors P. Scholtz, C. Saragiotis and P. TildyUtilization of dispersive surface waves is a promising technique for velocity model building of the near-surface. To analyse the dispersive properties of surface waves in case of a 3D reflection seismic acquisition, where surface waves are usually regarded as noise, we consider a recompression technique. Recompressive filtering collapses the long wave-train of dispersive waves into an impulse-like signal. This feature of the filtering method proved to be useful in wave type and wave mode separation, which is highlighted in this paper. When recompressive filtering is incorporated into an optimisation procedure the wavelet shape can drive the parameter estimation (dispersion curve and/or model parameters). We have developed a processing sequence, where traces of reflection records containing dispersive arrivals can be used to get information on the near-surface. On synthetic data we show how well the results of the recompression based Simulated Annealing optimisation works even in noisy conditions. The near-surface earth parameters which can be estimated with the help of recompressive filtering, presented in this paper, can support noise removal techniques, help the standard static calculations, intra-array perturbation correction, depth-velocity function estimation near the surface, etc. even in the latest 3D single source and/or single receiver field acquisition methods.
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Offset-Dependent Predictive Deconvolution
Authors R. Güney, H. Karsli and D. DondururPredictive deconvolution depends on the two important parameters, prediction distance (alpha) and operator length (N), and is commonly used to attenuate reverberation, short path and also long path multiples in seismic data. These parameters are generally used as constant along offset in routine processing. In this study, an offset-depended application procedure is developed in choice of the two parameters. It was observed that the use of the parameters based offset increased the performance of the predictive deconvolution rather than the constant parameters, leading to better stack and interpretable sections.
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Evaluation of Earthquake Hazard Parameters for the Different Regions in the Western Anatolia for Whole Time Periods
More LessThe earthquake hazard parameters are estimated for different regions of the Western Anatolian (WA). The whole examined area is divided into 15 seismic regions based on their seismotectonic regime. The database used in this work was taken from different sources and catalogues such as TURKNET, International Seismological Centre (ISC), Incorporated Research Institutions for Seismology (IRIS) and The Scientific and Technological Research Council of Turkey (TUBITAK) for historical and instrumental periods. The technique of maximum likelihood method is applied. The procedure allows the use of either historical or instrumental data or even a combination of them. By using this method the earthquake hazard parameters, which are the maximum magnitude, Mmax, mean seismic activity rate, λ, and the b-value which is the slope of the frequency-magnitude Gutenberg-Richter relationship, are estimated. Also, probabilities (Pr) for the occurrence of earthquakes of a specified size in a each region are evaluated. According to earthquake hazards parameters computed for each region Aegean Sea, Aegean Arc and Gölhisar-Çameli, Acıgöl and Tatarlı Kumdanlı Faults and Dinar Graben have highest hazard potential.
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Investigation of seismcity of the Marmara region with statistical approaches
By N. SayilEarthquake prediction researches keep an important place among the studies about the minimizing of earthquake damages. Great earthquakes in a characteristic region where is defined as seismogenic source take place recursively, but the time interval among these events varies from a seismogenic source to another. These changes do not only depend on a ratio of plate motions. Rupture length along the strike, the downdip width and the dip of the plate boundary are also effective factors on earthquake recurrence intervals. If a certain pattern is identified concerning changes in seismic activity in the hypocentral region after a large earthquake and leading up to the next large earthquake, an examination of the course of seismic activity will provide a lead to long-term forecasting of the occurrence of the next large earthquake. In order to estimate the recurrence intervals for large earthquakes occurred in the Marmara Region, this region limited with the coordinates 39°-42°K, 25°-32° has been separated into six seismogenic sources on the basis of certain seismological and geomorphological criteria. Poisson and exponential distribution methods have been applied for each source and recurrence times and seismic risk of earthquakes have been determined in the period of one hundred years.
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Statistical Assessment of Seismicity Pattern in Muğla and Rhodes Region, Turkey: Current Seismic Quiescence
More LessAn assessment of current seismic quiescence for Muğla and Rhodes region of Turkey using ZMAP software are studied. For this purpose, a quantitative study of the spatial distribution of the seismicity rate in the beginning of 2011 has been performed using standard deviate Z-value. Two regions with an apparently significant seismic quiescence are observed in the beginning of 2011. These areas are found centered at 37.32ºN-27.812ºE (around Milas and Yatağan) and 36.84ºN-28.712ºE (between Dalaman and Köyceğiz). These areas of seismic quiescence are recently observed and nearly started in the beginning of 2005. For this reason, special attention should be given to these regions where the seismic quiescence is observed. If such features could be recognized as a constant and reliable character of the seismicity, they could eventually contribute to the forecast of impending main shocks in future circumstances.
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Recent Seismotectonic Implications of the East Anatolian Fault Zone, Eastern Turkey
Authors A. Tan, H. Eyidogan, V. Gecgel, O. Tan, Z. Pabuccu and A. YorukAbstract One of most prominent and active faults in eastern Turkey is the NE-SW oriented left-lateral strike-slip East Anatolian Fault Zone (EAFZ) with a length of approximately 500 km. In this study, we have examined the recent seismicity of EAFZ that was obtained from the records of 34 3D broad-band earthquake stations established around the fault zone within TURDEP project since 2006. Further the seismicity and fault mechanism solutions of EAFZ, eastern Turkey have been examined. The new fault mechanism solutions in addition to previously published 220 earthquakes that occurred on the EAFZ between 1951 and 2010 were studied to understand the principal stress field and the seismo-tectonic characteristics along the fault zone. The new mechanism solutions of the earthquakes, with a magnitude of ML=2.0 or more were determined by a local moment tensor solution and P-wave first motion data. It is suggested that the recent tectonic deformation of EAFZ south of Turkoglu is taken up by the left-lateral strike-slip active faults in between Amik and Adana Basins where young trans-tensional stress regime is also active.
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Different crustal structures of the Istra and SW Pannonian basin from receiver functions modelling
Authors J. Orešković, F. Šumanovac, E. Hegedűs, S. Kolar and A.C. KovácsWe have used teleseismic events recorded at temporary seismic stations from the ALPASS-DIPS experiment to estimate the crustal structure of Istra peninsula and SW Pannonian basin. The data were analysed by P receiver function method based on the converted P-to-S phase generated at significant velocity discontinuities in the crust and upper mantle. Forward modelling of receiver functions was used to construct crustal shear-velocity models under the stations. The receiver function results can be compared with results from wide-angle seismic experiment in this area. The receiver functions analysis at stations deployed in Istra have showed that crustal velocity models fit to Dinaridic type with three major discontinuities within the crust. Whereas, models with single-layered crust could fit well observed receiver functions in the Pannonian basin. The crustal thickness for stations in the SW Pannonian basin is 25.5 – 28 km, and for Istrian stations it is in the range from 37 to 43 km.
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Some Seismotectonic Consequences of The W Black Sea Opening as Inferred from Geophysical Data
By L. BesutiuThe paper presents some crust to upper mantle geophysical imprints of the W Black Sea opening and seismotectonic consequences of this large event on the NW inland. Potential fields and seismic tomography are used as a tool
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Structural Impacts on Crustal Seismicity of Lake Van Basin (Eastern Turkey): Seismological Constraints for Crustal Defor
Authors M. Toker, S. Krastel, F. Demirel-Schlüter, E. Demirbağ and A.M. ŞengörOrogenic and seismically active lakes constitute only a few of the world’s lakes and do not produce the largest earthquakes. However, strike-slip lacustrine basins point to sharp mechanical changes at the bends along their faults, with specific implications for lacustrine earthquakes. Increasing attention has been paid to the micro and intermediate seismic events on the Highlands lacustrine environment “Lake Van basin” of Eastern Anatolia High Plateau (Eastern Turkey), creating solid base of seismic reflection and seismogram data for the estimation of structural characteristics of intra-plate earthquakes based on tectonic and sedimentary observations. Anomalous distribution of earthquake patterns and fault focal mechanisms in Lake Van underscore the need for better use of seismological and seismic structural information from the lake to understand its Highlands crustal seismicity and contribute to thin-skinned crustal deformation. Seismogram data clearly support overall deformation patterns shown by seismic sections and comparatively characterize them with the evolution of earthquake waveforms during magma migration and brittle faulting at volcanic stress conditions of the lake. This study has strong structural and seismological impacts on the surficial manifestation of volcano-seismicity and physical mechanism of tectono-magmatic processes all over Lake Van, significantly giving an evidence of “the Highlands lacustrine seismicity”.
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Water and its Effect on the Lithosphere-asthenosphere Boundary
By I. KovacsThe water in the Earth's upper mantle considerably lowers the melting temperature and this was investigated experimentally with the application of a novel experimental and analytical approach. It was shown that the instability of pargasite at depths greater than ~90km and at temperatures higher than 1000-1050 ºC leads to a sharp drop in the upper mantle's solidus temperature. It is speculated that this effect may define Earth's lithosphere–asthenosphere boundary at many geodynamic settings characterised by relatively high heat flow (>60 mW/m2).
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Stress Condition Determination based on Focal Mechanism Data: A Case Study on Kraljevo Earthquake
Authors A. Mladenovic and D. PetrovicThe aim of this research was to perform stress condition analysis in the area of Kraljevo, based on focal mechanism data of an earthquake from November 3rd 2010, as well as it’s three strongest aftershocks. Focal mechanisms of these earthquakes have been formed based on polarity of first arrivals of P-waves on seismic stations. Also, structural inversion of these data was performed. It was determined that, during investigated earthquakes, strike-slip faults of WSW-ENE were reactivated.
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Metamorphic Reactions as Indicators of Lower Crustal Processes during Formation of the Pannonian Basin
More LessThe Pannonian Basin is famous of its xenolith localities hosted by late Tertiary alkaline basalts, from different depths of the lithosphere. In this work we present the petrography, mineral chemistry, and geothermobarometry study of lower-crustal mafic garnet-granulite xenoliths from the central Pannonian Basin, namely from the Bakony-Balaton Highland Volcanic Field (BBHVF). Based on geothermobarometric calculations, the estimated pressure of the peak metamorpishm was about 1.0-1.6 GPa, at temperatures of about 800-1050 °C. Several reactions have been recognized in both the mafic garnet granulite and the metapelitic granulite xenoliths from the BBHVF, involved. The breakdown reaction of the garnet is the only reaction which can be observed both in metabasics and in metapelites. Experimental works and thermodynamic calculation show that the breakdown reaction of the garnet occurs at relatively low pressures of about 0.6-0.8 GPa. This pressure value is equivalent to 20-30 km depth which is equal with the present day depth of the lower crust. Reaction of garnet in metapelitic granulites shows similar or even slightly lower pressures. The metamorphic reactions show not only the thinning of the crust during the formation of the Pannonian Basin, but also make it possible to estimate the quantification of crustal thinning.
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Recent Tectonic Model of East (Iranian) Azerbaijan
By B. Zamani G.The stress analysis results in this study (by analytical method, for seismic and field data) have shown that there are two compressional stresses (NE-SW and NW-SE directions) in E-Azerbaijan Microplate. First stress system by NE-SW direction causes development of three tectonic grains, Arasbaran, Ahar and Bozkosh thrust sheets (fig. 3a). While, the second one (NE-SE direction stress system) causes the development of thrusts in N-S direction. Results show that thrusting leads to the development of tear faults in N-S and NE-SW directions with dextral strike-slip mechanisms. Also, development of young geological structures has good consistency with stress state in this area. These results could be developed as recent tectonic model of E-Azerbaijan. In this model materials are compressed in four sides of the E-Azerbaijan lozenge, while structures and materials escaped from north and Southern parts of this lozenge (fig. 3). The state of multiple stress system and the escape of material impose a left-lateral rotation to the E-Azerbaijan microplate (Fig. 3-b).
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New Interpretation of the Old ∆Z Anomaly Map of Hungary
More LessThe Hungarian magnetic vertical component anomalies were interpreted first more than 40 years ago by Posgay Since then, no one has conducted a country-wide interpretation and, unfortunately, there has not been any regional magnetic survey. However recent progresses in geological and geophysical knowledge allow a new, more complete analysis of the old magnetic anomaly map. The study of relationship between anomalies and geological structures and model calculations at some selected area resulted in the following interpretation. • Near the Austrian border the Penninicum represents a large-scale high-amplitude anomaly. In the territory of Little Hungarian Plane the visible anomaly is connected in Slovakia with the anomaly north of the Diósjenő line. The anomalies along the Balaton line continuing in direction to Buda and Recsk are caused by Eocene andesites. In South-Transdanubia both anomalies caused by serpentinites and basalts have characteristic curved shape which was formed during the Cretaceous. Anomalies located on the Great Hungarian Plane are caused by Cretaceous basalts and covered Miocene andesites. Miocene andesites and Mio-Pliocene basalts at the surface have intensive, rapidly changing anomalies. However it must be noted that to improve the interpration new magnetic survey and unification with data from the neighbouring countries is essential.
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Basalt Volcanoes under the Lake Balaton
More LessThe oldest volcano in the Bakony – Balaton-highland Volcanic Field is the Tihany Volcano (7,99-7,93 Ma). Due to its phreatomagmatic origin there was no lava flow onto the surface, one can find only tuffs and pyroclasts. In these pyroclasts there are volcanic bombs at multiple levels, derived from the ripped up basement clasts of the Balaton-highland. Reconstructed trajectories of these clasts suggest the existence of a volcanic center towards the East of the peninsula. According to the interpretation of seismic sections, recorded in the eastern part of the Lake Balaton, basalt intrusions can be present at a few places bellow the lake. In September 2010 we carried out magnetic survey in this area to confirm the seismic interpretation. We have acquired 14 north-south directed sections of the total magnetic field, with a complete length of 140 km. Correction of temporal variation of the field strength was performed on the basis of the continuous record in the Tihany geomagnetic observatory. After spatial correction based on the relevant normal formula, we arrived at a magnetic anomaly map. Although the resulting amplitude of the anomaly (30-40 nT) is lower than expected, it occurred exactly where the seismic interpretation indicated basaltic intrusions.
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Determination of Site Characteristics with Single Point Microtremor Measurements at the KTU Campus Area
By Y. BekerMicrotremor method used for engineering seismology is very important for determining of dynamic ground parameters and its variations. Method based on frequency of horizontal and vertical component microtremor records provides to quick and economical estimation of dynamic ground parameters. Most important advantage of Nakamura method defined as single station method isn’t required reference point and it can be applied easily in the area with low seismic density and without base rock. In this study, Nakamura (H/V) method has been applied to microtremor records taken with CMG-6TD three component broad band velocity seismometers in 6 profiles and 75 points with the aim of determining ground predominant period and magnification parameters of the (KTU) campus area of Black Sea Technical University in Turkey. Maps of magnification, predominant frequency and ground classification (Z1, Z3, Z4) according to the predominant period are created by derived values.
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Assessment of the Subsidence in Internal Maliqi Depression using Geophysical Methods
More LessThis study have covered the former Maliqi Swamp which of point view consists of the Quaternary overburden formations (Q1-4) and the Upper Neogene, concretely not differentiated Pliocene and Pliocene-Quaternary (N2-Q1) formations The main objectives (intention) are: - Investigation of the subsidence phenomenon, which may lead to the gradual formation of the Maliqi Swamp. - Locating on eventual second turf layer under the known one and its control with integrated methods. - The monitoring of the subsidence phenomenon To achieve a good result for above the objectives there have been used geodesics, geological and geophysical (VES) methods. The integrated interpretation of geodesic and geogolical-gephysical date allowed drawing the following main conclusion: - VES do not indicate the presence (at least up to70-80m) of e second turf layer; this is not a definitive conclusion. This conclusion can be verified by drilling up two holes 50m deep. - The youngest formations (swampy ones) are about 30-35m thick and composed of two fine grained argillaceous layers and two sandy-argillaceous layers. - The Maliqi Depression has been constantly having subsidence, at least since the swamp started to get dried out. In the period 1952-1977 the monitoring showed a vertical dipping from 0.5-3m
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