Mapping of thin sandy aquifers by using high resolution reflection seismics and 2-D electrical tomography |
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| Institution: | 1. Department of Statistics and Operations Research, Faculty of Science, Kuwait University, P.O.Box 5969, Safat 13060, Kuwait;2. Department of Mathematics, University of Ioannina, Ioannina 45110, Greece;3. Department of Business Administration, School of Business Administration, University of Macedonia, 156 Egnatia Str., Thessaloniki 54636, Greece;1. Royal Institute of Technology, Department of Energy Technology, Stockholm, Sweden;2. IMT Atlantique, Department of Energy Systems and Environment, UMR CNRS GEPEA, Nantes, France;1. Beach and Dune Systems Laboratory (BeaDS lab), School of the Environment Flinders University, Sturt Rd, Bedford Park, South Australia 5042, Australia;2. Laboratoire d''Océanologie et de Géosciences UMR CNRS 8187, Université du Littoral Côte d''Opale, 32 Ave Foch, 62930 Wimereux, France |
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| Abstract: | Electrical tomography, which gives good results even in fairly complex geological environments, has given a new lease of life to electrical methods in hydrogeological surveys. Nevertheless, a rapid decline in resolution with increasing depth remains the main problem of the electrical methods. In the Pannonian basin in Croatia, at a test area, combining both electrical tomography and seismic reflection methods provides data that better constrain the lithological and hydrogeological model of the subsurface.Electrical tomography revealed a rather thick packet of sediments with increased resistivity at depths of 40–100 m. Using the electrical forward modelling, the existence of two different hydrogeological models was shown. The first model presupposes a reasonably homogeneous packet of sandy clays or clayey sands, and the other model presupposes the alternation between layers of clays and sands. From the hydrogeological point of view, the second model is perspective, but unfortunately, the use of electrical tomography alone does not allow the ambiguity to be resolved. The separation of these two models became possible using seismic reflection. Three seismic environments were isolated from the seismic profile treated, and the strongest reflections were discovered in the first seismic environment, which covers the depths from 40 to 100 m. It was determined that the second model is more acceptable, because these reflections are caused by lithological changes, that is, the alternations of sands and clays. The interpretation is consistent with exploratory borehole data. The conclusion is that electrical tomography gives data concerning the sediment lithology up to depths of 40 m, but at greater depths combined interpretation of electrical and seismic data constrains the subsurface model better. |
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