Results of airborne EM groundwater exploration in a desert area using the centroid depth algorithm for evaluation
Sengpiel, K.-P. (1989). Results of airborne EM groundwater exploration in a desert area using the centroid depth algorithm for evaluation. Natuurwet. Tijdschr. 70(1-4): 349-356
In: Natuurwetenschappelijk Tijdschrift. L. Walschot/Natuur- en Geneeskundige Vennootschap: Gent. ISSN 0770-1748, meer
Ook verschenen in:De Breuck, W.; Walschot, L. (Ed.) (1989). Proceedings of the 10th Salt-Water Intrusion Meeting Ghent (Belgium), 16-20 May 1988. Natuurwetenschappelijk Tijdschrift, 70(1-4). Natuurwetenschappelijk Tijdschrift: Gent. 408 pp., meer
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Algorithms
Arid environments > Deserts
Exploration > Geophysical exploration > Electromagnetic exploration
Pakistan [Marine Regions]
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| Abstract |
Secondary magnetic-field data from a three-frequency electromagnetic (EM) helicopter survey have been evaluated using a novel inversion technique called the centroid depth algorithm. It yields the centroid depth z* of the electric current system (induced by a dipole source) and the "ambient" resistivity pa at this depth, both for each transmitted frequency. It is illustrated by several examples how the true vertical resistivity distribution is approximated by the p a (z*) function. For three transmitted frequencies this function is only partially known but it can be closely represented by a spline interpolation function. The complete, although approximate, resistivity information can be represented as vertical sections along flight lines or horizontal sections at certain preselected depths.Using these techniques the three-dimensional resistivity distribution below a non-perennial river in a desert area in Pakistan is shown and compared with Schlumberger resistivity soundings and results from drilling and dug wells. Several other fresh-water deposits in salt-water-bearing environments have been delineated using this airborne EM method. |
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