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7th Congress of the Balkan Geophysical Society
- Conference date: 07 Oct 2013 - 10 Oct 2013
- Location: Tirana, Albania
- ISBN: 978-90-73834-55-2
- Published: 07 October 2013
81 - 100 of 110 results
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Modeling Microgravity and DC-resistivity Response of a Longwall Mine at Soma-Darkale Coalfield
Authors E. Buyuk and A. KaramanAbstract. Estimating the footprint of a coal panel becomes important to resolve conflicts related to the adverse effects of longwall coalmining. The conflicts may be about permit boundary infringement, mitigating subsidence-induced hazard, or in some cases, avoiding the old production fields while projecting a panel and panel orientations. The utility of gravity and dc-resistivity methods provide valuable information when evidence such as fracturing and/or pre-, and post-subsidence deformation profiles are insufficient. Coalmine subsidence increases the secondary porosities of the overlying strata, which causes water-level drop because of increasing storage, and reduces the densities of the overlying rocks. With this study, we develop a 3-D gravity modeling code to account for the factors that are likely affect the geophysical measurements. We also address the factors that are likely violating the fundamental assumptions of the dc-resistivity measurements obtained over a subsided production panel. The geophysical data used in this study were acquired over a longwall mine panel at Soma-Darkale Coal field.
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A Tool for Analysing Depth Resolution in Potential-field Inversion
Authors V. Paoletti, M.F. Hansen, P.C. Hansen and M. FediA careful management of the ambiguities and errors in potential field inversion is crucial for obtaining reliable information about the source distribution with respect to depth. In this paper we introduce a tool, the ApproxDRP, which is based on an approximation of the singular vectors obtained by the iterative Lanczos bidiagonalization algorithm. This tool allows a computational/visual analysis of how much the depth resolution in a potential-field inversion problem is influenced by the way the problem is discretized and regularized. Since the ApproxDRP is based on an iterative method, it is suitable for large-scale problems. We show that when used in combination with a plot of the approximate SVD quantities, the ApproxDRP may successfully show the limitations of depth resolution resulting from noise in the data. This allows a reliable analysis of the retrievable depth information and effectively guides the user in choosing the optimal number of iterations, for a given problem.
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Waste Disposal Sites Investigation by the Use of Electrical Resistivity Tomography
Authors G.N. Vargemezis, P. Tsourlos, G. Tsokas, I. Fikos, N. Diamanti and A. StampolidisManagement of waste disposal is a major issue that authorities had and still have to deal with. The construction of landfills used to be the main way to manage the great volume of waste. At the present time, the construction of sanitary landfills is the dominant option in Greece, while old waste disposal sites where no protection standards had been followed still exist. In both cases, geological and hydrogeological setting of these areas is of a major importance. In this paper, two cases studies are presented. One case refers, to the active sanitary landfill of Thessaloniki where during the remediation of a new cell, underground water has been found. This was a major problem for the construction of the new landfill since water flow beneath the geomembrane can be destructive. The detection of the flow path and the confrontation of the problem was very important. Resistivity survey allowed the mapping of the underground water flow and appropriate measures have been taken according to the suggestions of the geophysical results. In the second case, an old waste disposal site has been investigated since outflows of leakage occurred. The flow paths of the leakage have been detected and remediation measures have been suggested.
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Determination of Uranium, Thorium and Potassium
By Ema DodonaGamma spectrometric method is used for determination of U, Th and K in laboratory and field conditions. For this purpose a gamma spectroscopic instrument GAD-6 with NaI detector was used. The study and experimentation of the main factors like geometry and calibration which influenced in the gamma spectrometry measurements was performed. Calibration procedures were carried out based in rock samples preparation, recommended by IAEA. Through the mentioned methods were analyzed thousand of rock samples for the U, Th and K content determination with great precision and low cost.
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A Review of the Scientific Studies Published in the Radiogeochemical-Radiometric Bulletins during 1949-2000 Years
By A. DodonaThis bibliography is prepared for the sake of 100 anniversary of radioactivity discovery by H. Becquerel about the Uranium (1896), and the first perception of Radium done by Pier & Marie Curi (1898), whom in relation with this were honored with Nobel Reward (1903). The philosophy of such discover remind us A. Flemings saying: “Never left apart the things that seem to be strange or uncommon, often they may be false alarm, but may be even the key of an important truth”. Instead its value and importance is expressed in significant saying of A. Einstein “,,Radioactivity phenomena representative most revolutionary force of technical progress since from the time of the fire discovered by prehistoric man”.
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Basin Evolution and Hydrocarbon Plays in Albania
More LessA new geodynamic model based on structural and kinematic observations is presented here that predicts that anticlockwise rotation of the Apulia foreland along with its uplifted promontory in the southwest of Albania provided a buffer stop for the incoming ‘train’ of the Ionian basin thrusts during the Oligocene to Pliocene. A regional shear couple was formed between the hinterland and the buffer stop which was accommodated by strain partitioning along the strike. The Ionian basin thrusts were uplifted and exhumed in the south as they buttressed towards the promontory, while propagating freely in the north towards the foreland and overlain by Durresi foredeep basin during the Miocene – Pliocene.
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The Influence of the Shear-wave’s Velocity Variation on the Response of the Geotechnical Models - a Case Study
By E. VeseliIt is well known that the soil response to the earthquake motion depends on the various parameters describing the layers over the bedrock. We analyze one of the geotechnical models of the Tirana City and try to find the influence of the shear-wave velocity variations over the sedimentary cover on this response. We compare the original model formulated at the end of 80-s in terms of VS with new measurements of this parameter carried out through down-hole and MASW techniques, keeping on the same time other parameters constant. The earthquake motion was propagated through the same column, but with three different VS values for the uppermost part of the section. A different pronounced response was noted for each case, indicating that modification of the old model’s VS parameter on a site-by-site case should be carried out before using the soil response analysis data for design purposes.
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Late Pleistocene – Holocene Seismic Records of a Sand Ridge at the Southern Exit of Istanbul Strait, Turkey
More LessThe stratigraphic setting and morphotectonic development of a wedge-shaped sand ridge, 2 km long and 600 m wide, on the southern approaches of the Strait of Istanbul has been investigated using high resolution chirp data. On a ravinement surface it is evolved during the post-glacial sea-level rise in the Sea of Marmara (late Pleistocene-early Holocene). The dynamics of sea bottom sediments, estimated from net sediment transport pathways by applying grain trend analysis, implied that the shallow depression channel behind the sand ridge is one of the much suitable depositional environments.
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Geotechnical Problems Caused by Unknown Cellars
More LessSome months ago there was a collapse in a public park in Budapest, Hungary. On the location called Kőbánya the limestone was covered by 10-30 m of good quality clay. For that reason clay was excavated in general in open-pit mines while limestone was exploited in quarries and in underground tunnels as well. The main reason of the accident was consideret to be the collapse of an unknown tunnel or cellar. The surroundings of the void was investigated by different gophysical metods to find the reason of the event and to map the potencial location of latter collapses. DC geoelectric, GPR, seismic diffraction and tomogrphic methods were applied. The findings were proven by drillings and CPT soundings.
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Determination of Soil–structure Response by Using Microtremor Measurements in Bornova, İzmir (Turkey)
Authors E. Pamuk, S. Turan, F. Onsen and S. KarabulutUnderstanding the seismic behavior of buildings during the earthquakes is very important. Microtremor measurements are required to estimate the resonance frequency of soil and buildings . HV spectral ratio technique is widely used in urban environment to assess the fundamental frequency response of the ground. Therefore, the H/V spectral ratio was calculated with this method. The measurements were taken inside the building basement floor, third floor, fifth floor and eighth floor. 150 m on southwest of the building is selected as the garden point. It is noticed that if the number of floors increases, predominant frequencies decrease and H/V ratios increase. The amplitude spectral analysis of the all points was carried out to determinate the spectral characteristics of soil and building. The amplitude spectrums of all data were compared with each other. It points that significant increasing of amplitude values are interested with increasing of the floor numbers. Therefore, the highest amplitudes are obtained on the top floor. The amplitude values of horizontal components are greater than vertical component at the floors 3rd ,5th and 8th. However, we observed similar values at basement point and outside point at all components.
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Site Condition Mapping using Topographic Slopes
More LessWe investigate the possibility of adaptation a new method for large scale assessment of seismic site conditions and amplification, by using maps derived from topographic data, making the technique quick and cost effective. The maps uses topography slopes as a proxy for site conditions, based on its close connection to the results of shear wave velocity measurements proved by previously accomplished correlation calculations. The technique was investigated on a test site in Hungary by using SRTM 3 sec maps and VS,30 (average shear wave velocity down to 30 m) results of surface wave measurements carried out previously. Our results show that the measured and calculated VS,30 values are close to one another, but in case of the test and similar areas (characterized by consolidated alluvial deposits) the velocity values scatter around the important boundary level (360 m/s) of “B” and “C” categories. Consequently some refinement of correlation and involving geologic data can be necessary and useful for a more accurate classification.
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Modelling of the Shallow Structures of Cappadocia Region by Gravity Method
Authors Ö. Bektaş, S. Koşaroğlu, A. Büyüksaraç and A. AteşCentral Anatolia and the surrounding area for many researchers engaged in studies concerning the origin of the tectonic and volcanic activities are examined, which is composed of tectonic units in Cappadocia is different based on the findings, many researchers have obtained different results. In this study, using a 2.5-D and 3-dimensional models of gravity data and the work area made of low-density, loosely defined thickness of the upper structure. Working in the field surveys conducted in recent years, volcanic studies, hydrocarbon and geothermal research, field research has revealed the need to describe the relationship between deep and shallow structure. In addition, studies so far out in the study area is shallow and low-density units on the caldera is showing some of the basic approaches to feature-reach, within the scope of this thesis are among the targeted results.
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Direct Targeting of VMS through Amplitude Consistent Seismic Imaging
Authors S. Yavuz, J. Kinkela, A. Greenwood, M. Penney, V. Araujo, R. Neto, A. Dzunic and M. UrosevicBased on physical property measurements of core samples and the often observed difference in elastic properties from these there should be a significant difference in seismic amplitude between mineralisation and the surrounding host rocks. These results indicate that relative amplitude preservation processing may be of importance in the use of seismic data for the targeting of mineral resources, particularly in the case of massive ores. Such ‘true relative amplitude’ processing is not easy to achieve due to intrinsically low signal to noise ratio in hard rock environments, complex 3D geology, steeply dipping structures, high seismic velocities and often patchy and poor reflectivity. To help reduce the ambiguity in targeting and increase the likelihood of success we have worked on careful re-processing of 3D seismic data with the application of true amplitude preservation. We compare the anomalous amplitude zones that are related to massive sulphide bodies using a true amplitude seismic cube and a conventionally processed cube with the application of AGC (automatic gain control). A higher level comparison is conducted after seismic calibration with boreholes. The zonation and precision of targeting is discussed in this paper.
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Time-frequency Analysis of Georgia Earthquake (25 December 2012)
More LessSeismic waves that observed in earthquake records are non-stationary typical. To better understand the structure of the seismic signals, not only is enough to examine changes at time domain, also frequency domain is shows a component characteristics of the signal important. Therefore in recent years, different time-frequency analysis methods are used extensively. Time-Frequency analysis is suitable for non- stationary signal analysis and processing. Time-frequency analysis contains a signal in both time domain and frequency domain at the same time. In this study we applied and compared a linear and a quadratic two different time-frequency analysis methods short-time Fourier transform and Wigner-Ville distribution in December 25, 2012 Georgia earthquake record. As a result of this study, short-time Fourier transform method gave better results than the Wigner-Ville distribution.
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Resistivity (ERT) Prospection in Tropaeum Traiani Roman City
More LessTropaeum Traiani archaeological site consists of ruins of an ancient city and a triumphal monument built after a victorious Roman campaign against Dacians during the winter in 102 AD. Civitas Tropaensium started as a castrum and became a municipium around 200 AD. The main archaeological interests presented as geophysical tasks to the geophysical prospection were the remnants of the first Roman stage of the city (first century AD), impossible to excavate and directly study due to the legal protection of the shallowest remains of ancient constructions, dating from the second Roman stage of the city (started during Constantin the Great, IVth century AD). Geophysical profiles of Electric Resistivity Tomography (ERT) were carried out in the area of Basilica Forensis and along Via Principalis. The two levels of high resistivity anomalies illustrated on the Via Principalis ancient street were interpreted as remnants of limestone pavement and constructions walls, remains of the second stage of the city, and of the first stage respectively. The resistivity survey inside Basilica Forensis shown also two levels with high resistivity anomalies, interpreted to be associated with the basilica inner pavement and its infrastructure.
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Diffraction Imaging Using Plane-wave Destructor Filters in Common-depth Specularity Gathers
Authors T.J. Moser, I. Sturzu, A.M. Popovici, I. Musat and N. TanushevSeismic diffraction imaging is recognized as a rapidly emerging technology with great potential to reduce exploration and production risks and increase recovery, for conventional reservoirs as well as unconventional resources such as shale gas. The idea behind diffraction imaging in a pre-stack migration framework is to apply a weight factor inside the migration loops, which attenuates events that satisfy Snell's law of specular reflection, while preserving diffractive events that do not satisfy Snell's law. Here we further develop an approach, called specularity gathers, to construct the weight factor in a very efficient way. We introduce a method to filter the specular energy from specularity gathers in order to obtain diffraction images. The use of a filter like plane-wave destructor enables an automatic algorithm, but leaves the option for interactive updates based on interpretation input as well. Further development of this method will help in advancing diffraction imaging technology.
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Some Results for 3D Gravity Inversion in Parallel Systems
Authors N. Frasheri, S. Bushati, A. Frasheri and B. CicoThe aim of the paper is presentation of some results obtained for the 3D gravity inversion in high performance parallel computer systems (HPC). Calculations were based on CLEAN algorithm parallelized with OpenMP and MPI using HPC capacities offered by FP7 project HP-SEE. Scalability of runtime in terms of model sizes and number of computing cores was analyzed. The quality of inversion was evaluated for single and two body models, and concrete tests with field data were carried out. Runtime analysis results matched theoretical expectations for the order of magnitude of calculation time O(N^8) where N represents the linear size of the geosection, and permitted an evaluation of effective runtime for small and medium models. Two modified least squares schemes were applied for the inversion of multi-modal anomalies and respective errors compared. The link between symmetries of geosections and respective anomaly approximation errors was observed. Obtained inverted geosections are characterized by distinguished contrast of mass density between anomalous bodies and surrounding rocks. But more work is required to deal with multi-body geosections (multi-modal anomalies) to reduce the lack of discrimination capacity of the algorithm for in-depth bodies.
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Preliminary Results from DANA Array on the Crustal Structure of the Western Segment of NAF
Authors N. Turkelli, M. Kahraman, S.A. Poyraz, M.U. Teoman, S. Rost, G.A. Houseman, D. Thompson, D. Cornwell, M. Utkucu and L. GulenThis study focuses on upper crustal studies such as earthquake locations (especially micro-seismic activity), moment tensor inversions and receiver function analysis. Accurate earthquake locations will eventually lead to high-resolution seismic images of NAF including both the northern and the southern branches in the upper crust.In this study, 722 earthquakes within the time period of 09 May – 17 September 2012 were located. Furthermore, the crustal structure beneath the DANA Array is investigated using receiver functions obtained from the teleseismic recordings from a total of 73 broadband stations. Calculated Moho depth beneath the most of stations is between 33 and 36 km.
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Seısmıc Rısk Analysıs of Sapanca Dıstrıct
By M. SaygiIn and around the lake sapanca the environmental impact of earthquakes and seismic risk analysis
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Exploration of Buried Cannons Using Magnetic and GPR Methods in Canakkale, Turkey
Authors A. Büyüksaraç, C.Ç. Yalçiner, Y.C. Kurban, M.İ. Topçu and B. SayilirThe old Ottoman fort of Kumkale lies 5 km from the ruins of ancient Troy and 45 kilometres south of Çanakkale, Turkey. The fort dates from the 17th century and was built as part of the outer defences of the Straits. From the Kumkale area there are fine views to Gallipoli Peninsula and Dardanelles, and throughout the campaign Turkish batteries hereabouts bombarded Allied positions at Helles. The French fleet had stationed in front of Kumkale shore, Çanakkale, during World War I on 25th of April, 1915. Turkish Cannons in the batteries bombarded the fleet, however, they were not be able to complete their duty. French soldiers landed under protective bombardments of the navy targeting Kumkale and Orhaniye. After that all cannons were destroyed by allied soldiers. The ruins of the cannons were buried and disappeared at site. However, army has plans of the batteries and places of them were approximately known by historians. That’s why a geophysical survey campaign was planned to find the old cannons. In the frame of geophysical survey, magnetic and GPR methods were applied. Figure 2 shows profile map for both of these methods. Of course magnetic method was more successful in prospecting the heavy and huge iron cannons.
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