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Near Surface 2008 - 14th EAGE European Meeting of Environmental and Engineering Geophysics
- Conference date: 15 Sep 2008 - 17 Sep 2008
- Location: Kraków, Poland
- ISBN: 978-90-73781-56-6
- Published: 17 September 2008
81 - 100 of 130 results
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Estimating Sinkhole Hazard in the Dead Sea Coastal Area Using P-wave Velocities and Magnetic Resonance Soundings
Authors A. Legchenko, M. Ezersky, M. Boucher, C. Camerlynck, A. Al-Zoubi and K. ChalikakisWe propose a geophysical tool for estimating sinkhole hazard in the Dead Sea coastal area in Israel and Jordan. This tool is based on joint use of seismic refraction and Magnetic Resonance Sounding (MRS) methods. Application of this approach in Nahal Hever south (Israel) and Ghor al Haditha (Jordan) reveals its efficiency. Obtained results are in a good agreement with other data available. It has been found that after sinkhole development subsurface caverns are refilled by rocks both in Israel and Jordan. Development of new caverns was not observed. Our results suggest that areas actually exposed to sinkholes disaster could be safely used in the future.
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Combining Seismic and CSAMT Methods in a Sinkhole Site Study
Authors B. Benjumea, J. Ledo, E. Falgàs and S. FiguerasThe Catalan Potasic Basin (Northeast of Spain) has been associated with subsidence and structural failures due to sinkholes influenced by salt mining activities. The study area contains three visible sinkholes developed in 60s, 2000 and 2002. Questions regarding the subsoil extension of the collapse/drainage zone and the mechanism of sinkhole formation are under study. Complex geology and presence of different materials susceptible to dissolution make difficult to understand the process based only on outcrop and borehole information. In this work, we present the combination of two geophysical techniques, seismic and Control Source Audiomagnetotelluric (CSAMT) methods, in order to delineate subsurface anomalies associated with the sinkhole formation. Combining both seismic velocity and resistivity models constrain the interpretation and helps to find high-porosity zones associated with sediment displacement and to define the evaporitic rock top.
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3D GPR Measurements for Sinkholes Detection – Case Studies from Selected Sites in Poland
Authors H. Marcak, T. Golebiowski and S. Tomecka-SuchonThe paper presents 3D GPR investigations for location voids and loose zones in two sites in Poland: first on the area of the Old Town of Sandomierz and second at the post-mining area in the town of Siersza. The appearance of the viods and loose zones in the ground influence on the changes of the dielectric properties of the geological medium, mainly when such zones are water-saturated. The results of GPR deta interpretation allow to predict sinkhole creation in both sites under investigation.
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Geophysical Investigation of a Sinkhole Feature in Schleswig-Holstein
Authors H. Wiederhold, B. Gebregziabher and R. KirschAn area in northern Germany where recently several sinkholes occurred is investigated by several geophysical methods (e.g. seismic reflection with P and S-waves, vertical electrical soundings, cone penetration tests). First results are discussed with respect to the genesis of the sinkholes.
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2D Resistivity Imaging of an Anisotropic 3D Body – Results of a Laboratory Experiment
More LessA simplified 3D model of a vertically “fissured” underground object was studied with 2D resistivity imaging at laboratory scale. The model was built with insulator sheets forming a parallelepiped “cake” embedded in a homogeneous medium (water). Both apparent resistivity of cross-sections and inverted models are complex and depend on the direction of the measuring line in relation to the “fissures”.
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The Near-surface Visualization of Underground Structure by Means of Seismic Holography with Suppression of the d.c.-Term
By Z.M. MotykaThe method of the d.c.-term digital suppression was used to obtain enhanced numerical reconstruction of earlier recorded seismic phase-amplitude hologram of near-surface objects.
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Integrated Analysis of Potential and Seismic Data Using the Geostatistical Approach
More LessThe aim of the present paper is to develop a method that integrates various geophysical methods with different resolutions and physical properties of interest. To carry out a more reasonable analysis, geostatistical approaches were used. For maximizing the benefit of integration, potential and seismic data, which have opposite characteristics, were used. The potential method has a low vertical resolution but a significant advantage in the study of the structure of a wide area at a low cost. The seismic method has high vertical resolutions but can include substantial cost and effort. In our processing, the vertical resolution of the seismic data and magnetic distribution were used to evaluate the gravity analysis. And the spatial distribution of the corrected gravity data was used to re-analyze the result of the seismic data with the evaluated validity. The proposed method was tested using a hypothetical model and field data from a real intrusive igneous area. The results of the model test agreed well with those of the real model. Moreover, with the real field data, the geostatistical approach used herein demonstrated relatively satisfactory results. So, the newly proposed integration analysis could be used effectively for the analysis of multi-geophysical data.
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Repeated Electrical Resistivity Acquisitions with Buried Permanent Equipment – Estimation of the Noise
Authors M. Peter-Borie, C. Sirieix, V. Naudet and J. RissIn order to monitor the water saturation of an unstable cliff formed by weathered rock in the region of the Cote Basque (France), a permanent electrical array has been installed. This array is composed of forty-eight steel electrodes embedded in a trench since January 2006. In order to determine variations in electrical resistivity values due to noise and those that could be associated to water content variations, repeatability tests have been realised with the same array in the shortest time. The statistical analyses of the results show that the first measurement of a day is significantly different from the other. This result could be explained by a polarisation of the system array-clay at the time of the first acquisition. Furthermore, despite the removal of the first acquisition of the day, a residual noise is still recorded at the foot of the cliff. This area, also characterised by rapid and high variations of spontaneous polarisation, seems to be affected by rapid water flows. These repeatability tests performed thanks to a rapid resistivity-meter, allows, firstly, removing the cause of the major noise, and, secondly, allows locating areas where electrical resistivity values cannot be stabilized because of water flow.
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Adding Corrections to Apparent Conductivity Values Measured in Low-frequency Induction Profiling
By J. AntoniukAn analysis of conditions, under which formulas for apparent conductivity were derived for low-frequency induction measurements, was made. The values of errors resulting from nonfulfillment of the asymptotic conditions were evaluated for measurements made with ground conductivity meters produced by the Geonics Ltd. A concept and way of adding corrections to measured values of apparent conductivity are presented. Examples of correcting apparent cnductivity values obtained both from terrain measurements and mathematical modeling are given.
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The New "Maximum Yield Grid" (MYG) Array in Full 3D Resistivity Tomography
Authors G. Fiandaca and P.L. CosentinoOver the past few years geoelectrical prospecting has experienced many innovations, ranging from instrumental refinements to improvement of data interpretation. The consequence of this has been a strong increase in the method’s resolution power and, therefore, its field of application has broadened. Nevertheless, the diffusion of 3D surveys in electrical resistivity tomography has been very much limited by the long acquisition time required by this kind of investigation, as compared to 2D ERT or other geophysical exploration methods like GPR. However, 3D ERT has a great advantage in terms of resolution power, that is very important in many applications, such as archeological or cultural heritage surveys. Furthermore, the applicability of DC electrical resistivity tomography to media with precious and vulnerable exposed surfaces in the field of cultural heritage, has also been limited by the invasivity of geoelectrical prospecting: in fact it is usually necessary to insert the electrodes for current injections into small perforations on the acquisition surface. To overcome these limitations a new 3D array, named MYG, has been developed to minimize acquisition time (40 times smaller than that of classical arrays) and the invasivity of 3D ERT, and to enlarge its field of application in geophysical prospecting.
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The Effect of Finite Electrodes on ERT Measurements Simulated with the Complete Electrode Model
Authors C. Rücker, J. Igel, M. Furche and T. GüntherIn the inversion of ERT measurements we usually treat the electrodes as points. However, for small-scale arrays, e.g. lysimeter studies, this assumption may lead to severe misinterpretations. We present a method to incorporate both the electrode shape and its contact impedance in the finite element simulation using the complete electrode model. We show that for small-scale measurements the electrode shape can affect the measurements significantly.
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A New Approach for Routine Investigation of the Shallow Sea Floor with Bottom-towed DC Resistivity Measurements
Authors T. Guenther and W. SüdekumWe present a new approach for routinely investigating the shallow sea-floor. Hardware is a dedicated multi-electrode cable that is towed above the bottom and additional sensors for determining geometry. Data processing is achieved by a harmonic least squares fit representing a spatial stacking of the data. The resistivity distribution is obtained by a fast and on-situ 1d inversion, a roll-along 2d inversion and a detailed analysis using finite elements.
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Locating an Active Fault by Two-dimensional Joint Inversion of Radiomagnetotelluric and Direct Current Resistivity Data
Authors M.E. Candansayar and B. TezkanWe investigate an active fault by using radiomagnetotelluric (RMT) and direct current resistivity (DCR) method. RMT and DCR field data set observed across an active fault located close to the city of Kerpen in Germany. First, the synthetic RMT and DCR data is generated for similar model expected from the investigated field geology. The individual and 2D joint inversion results of these data sets were compared and we demonstrated that the 2D joint inversion result based on this synthetic data simulates the real model more accurately than the 2D inversion results of each individual method. Then, the field RMT and DCR data are inverted individually and jointly and showed that 2D joint inversion of two data sets are better shows fault location and depth from the surface then the individual data set inversion.
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Estimation of Parameters of Contaminated Ground Layers Using Electromagmetic Waves Hodographs
Authors A.A. Dolgiy, A. Dolgiy, V. Markulis and V. ZolotarevIn this paper practical results of the long-term (1999-2007) application of Ground Penetrating Radar (GPR) technique for estimation of electrical parameters of contaminated ground layers are presented. Contaminations were caused by oil products. GPR technique includes the procedures of profiling, taking hodographs according to the Common-Midpoint (CMP) method and data optimal processing. GPR data processing was applied to acquire the estimations of values of ground layers thickness and their relative dielectric permittivity ε by solving the GPR inverse problem. For data processing were used the methods of weighted least squares, the recursive Kalman filter, the maximum likelihood and the Nelder-Mead optimization. The comparative analysis of these methods allows to define the most expedient technique for the practical estimation of the ground electrical parameters using GPR data. The acquired values of ε were connected with the degree of ground contamination which was attested by measurements of a floating layer thickness of oil products in the observation wells and their concentration in the ground. The monitoring data acquired in 2007 shows in comparison with the year 2006 the values of ground contamination degree estimated by GPR technique were decreased from 2.7% up to 58.8% for different observation wells. These decreases were confirmed by measurements in the observation wells.
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Electrical Conductivity of Soil Contaminated with Post-mining Zn-Pb Wastes
Authors M. Kondracka and A. Wysowska-SwiebodzinskaPreliminary tests were performed to evaluate the electrical conductivity of soils and analyse the effect of water content on soils contaminated with post-mining wastes . Depending on soil type different electrical conductivity (EC) and different relations between electrical conductivity and water content were observed. The soils contaminated with post-flotation wastes were characterized by much higher electrical conductivity (EC=1,5 – 8,3 mS/m) than the soils contaminated with post-launder wastes (EC=0,8 – 0,9 mS/m). This relationship was linear for the samples of uncontaminated soils and contaminated with post-launder wastes while for the soil samples contaminated with post-flotation wastes this relationship was exponential.
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Geoelectrical Survey in the Area of a Long-lasting Zn-Pb Waste Storage
Authors B. Zogala, J. Pierwola, R. Dubiel and J. CabalaThis paper presents the results of geoelectrical study of the former Zn-Pb processing waste-dump situated in the Olkusz region , southern Poland. In the past two kinds of waste were stored in this place. One is the washing waste, the other consists of tailings. A certain amount of them was processed in the first half of the 20th century. At present more than ten thousand tons remain on the stockyard. The results of the chemical analysis show that the contents of metals such as Zn, Pb, Cd and Tl exceed several orders of magnitude standards established for industrial soil. Under the low pH value mobility of these elements is significant. Unfavourable geological conditions can cause the migration into the underground water. In the study area the electromagnetical method was applied to study the boundaries between waste and unpolluted soil. The resistivity method was taken to define the vertical range of waste and to identify layers lying below the waste level. Our investigation points that geoelectrical methods can be successfully used for contouring Zn-Pb waste.
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Preliminary Results of Displacements Monitoring from Radar Interferometry in the Area of "Kazimierz-Juliusz" Coal Mine
Authors S. Porzycka and A. LesniakIn this paper the analysis of satellite radar interferometry data (PSInSAR data) was presented. These data concern mining area of “Kazimierz-Juliusz” coal mine and they supply information about small, long-period surface displacements, which occur there. PSInSAR data have been compared with conventional leveling, GPS and InSAR data. They were also compared with locations of the exploitation fields. Paper provides basic information connected with technique of the radar scenes processing (PSInSAR) and presents description of the available PSInSAR data as well as characteristic of “Kazimierz-Juliusz” mining area.
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Monitoring Resistivity in Non-hazardous Waste Landfill Using Time Domain Electromagnetism (Drôme, France)
Authors M. Descloitres, J.P. Laurent, C. Morra, R. Clément, L. Oxarango and J.P. GourcGeophysical surveys using resistivity methods have been carried out since 2007 at an experimental landfill site (Drôme, France) as a part of ANR French research projects “Bioréacteur” and “Envirhonalp” aiming at optimizing landfill biodegradation of non-hazardous municipal wastes. The objective of the present study is to propose efficient methods to monitor resistivity variations with time using non-destructive and low cost methodology. We experiment an alternative and complementary approach to resistivity (DC) methods using Time Domain Electromagnetism (TDEM). This method is non-destructive, sounds deeply without large extension at the surface, is very sensitive to the conductivity of the ground, and can be used without using electrodes. We present the first results obtained when monitoring resistivity of a cell of 125 000 m3 over one year using time-lapse TDEM. The results are compared to neutron logging and gamma densimetry monitoring. We found that resistivity is not changing with time on this site. A TDEM synthetic modelling is presented to demonstrate the sensitivity of time-lapse TDEM to resistivity changes. Finally, we conclude that TDEM can be an efficient alternative to DC resistivity method for resistivity monitoring related to bio-degradation.
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Geoelectrical Signature of Hydrocarbons – A Case Study
More LessThe detection of the organic contaminants, such as hydrocarbons commonly known as LNAPL in the ground has become of great interest to the geophysicists particularly in the last few years. A detailed geophysical survey has been planned based primarily on the use of the electrical resistivity methods, to locate groundwater contamination sources. The geophysical signature of the hydrocarbon contamination has been discussed in this work.
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Study on Detection of Hydrocarbon Pollution of Soil and Groundwater with the Use of Geophysical Methods
Authors A. Wójcicki, G. Pacanowski, T. Golebiowski, H. Marcak and S. Tomecka-SuchonThe study has been carried out in the frames of an ongoing R&D project “Study on detection of hydrocarbon pollution of soil and groundwater with the use of geophysical methods” supported by Polish Ministry of Science and Higher Education and Programme of Structural Funds “Competitiveness”. The overall goal of the project was to utilize related knowledge and expertise of research partner – AGH University of Science and Technology in order to help the contractor, service company - PBG Geophysical Exploration Company Warsaw Ltd, developing an methodology on the effective use of geophysical methods to detection and monitoring of hydrocarbon pollution on areas of old oil fields. These areas are are intended in not to distant future to be converted for the use of local communities. Results of geophysical ERT and GPR surveys can be used to detect contaminated zones within groundwater and soil system if they are correlated with results of computer simulations of electromagnetic wave field and within contaminated soil and numerical modelling of hydrocarbon pollution range and fate within characteristic types of ground (and aquifers).
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