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Error in depth determination from resistivity soundings due to non-identification of suppressed layers
The magnitude of errors in the determination of depth to bedrock from Wenner and Schlumberger resistivity sounding curves, caused by the nonidentification of a suppressed layer, has been investigated. The principal objective is to evaluate how the layer thicknesses and resistivities affect the accur...
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1997
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| LEADER | 00000njm a2000000a 4500 | ||
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| 001 | oai:repository.ui.edu.ng:123456789/5432 | ||
| 042 | |a dc | ||
| 720 | |a Olayinka, A.I. |e author | ||
| 260 | |c 1997 | ||
| 520 | |a The magnitude of errors in the determination of depth to bedrock from Wenner and Schlumberger resistivity sounding curves, caused by the nonidentification of a suppressed layer, has been investigated. The principal objective is to evaluate how the layer thicknesses and resistivities affect the accuracy of depth estimates. In the computations, the intermediate layer in a 3-layer model, in which the resistivity increases with depth, is removed and the 2-layer sounding curve that is electrically equivalent to the 3-layer curve is generated. The results indicate that there is a possibility for large depth underestimations when the resistivity contrast between layers 1 and 2 is very large. This is manifested in a steeply rising terminal branch on the sounding curve. There is a slight decrease in the depth underestimation as the resistivity contrast between layers 2 and 3 increases. Conversely, if the intermediate layer is fairly thick and the resistivity contrasts are not too large, the best-fit 2-layer curve shows large deviations from the 3-layer curve, in such cases, the intermediate layer can be identified, resulting in reliable depth estimates. A field example from Nigeria is presented in which the sounding data has been interpreted so as to account for a prebasement layer of intermediate resistivity, indicative of a fractured granite. | ||
| 024 | 8 | |a ui_art_olayinka_error_1997 | |
| 024 | 8 | |a Journal of African Earth Sciences 24(4). Pp. 635-647. | |
| 024 | 8 | |a http://ir.library.ui.edu.ng/handle/123456789/5432 | |
| 245 | 0 | 0 | |a Error in depth determination from resistivity soundings due to non-identification of suppressed layers |