Electrical imaging of lateritic weathering mantles over granitic and metamorphic basement of eastern Senegal, West Africa

Ritz, Michel; Parisot, Jean-Claude; Diouf, S.; Beauvais, Anicet; Dione, F; Niang, M.

doi:10.1016/s0926-9851(99)00008-7

Cited by 60 publications

(22 citation statements)

References 9 publications

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“…Two-dimensional resistivity and I.P. imaging surveys are now widely used for various engineering, environmental, and mining studies (Griffiths and Barker, 1993;Barker, 1996;Dahlin, 1996;Ritz et al, 1999). Such surveys are usually carried out using a large number of electrodes (25 or more) connected by a multi-core cable to a resistivity meter system ( Figure 1a) with an automatic switching unit (Griffiths and Barker, 1993).…”

Section: Introductionmentioning

confidence: 99%

A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys

Loke

Acworth²,

Dahlin

2003

Exploration Geophysics

809

396

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Two-dimensional electrical imaging surveys are now widely used in engineering and environmental surveys to map moderately complex structures. In order to adequately resolve such structures with arbitrary resistivity distributions, the regularised least-squares optimisation method with a cell-based model is frequently used in the inversion of the electrical imaging data. The L 2 norm based least-squares optimisation method that attempts to minimise the sum of squares of the spatial changes in the model resistivity is often used. The resulting inversion model has a smooth variation in the resistivity values. In cases where the true subsurface resistivity consists of several regions that are approximately homogenous internally and separated by sharp boundaries, the result obtained by the smooth inversion method is not optimal. It tends to smear out the boundaries and give resistivity values that are too low or too high. The blocky or L 1 norm optimisation method can be used for such situations. This method attempts to minimise the sum of the absolute values of the spatial changes in the model resistivity. It tends to produce models with regions that are piecewise constant and separated by sharp boundaries. Results from tests of the smooth and blocky inversion methods with several synthetic and field data sets highlight the strengths and weaknesses of both methods. The smooth inversion method gives better results for areas where the subsurface resistivity changes in a gradual manner, while the blocky inversion method gives significantly better results where there are sharp boundaries. While fast computers and software have made the task of interpreting data from electrical imaging surveys much easier, it remains the responsibility of the interpreter to choose the appropriate tool for the task based on the available geological information.

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Section: Introductionmentioning

confidence: 99%

A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys

Loke

Acworth²,

Dahlin

2003

Exploration Geophysics

809

396

View full text Add to dashboard Cite

show abstract

“…) or the application of other geophysical methods (seismic reflection and refraction, gravity) to validate the results obtained. Some recent works have shown that the application of resistivity methods can reveal very important details of the weathered zones, the hydrological system, and geological structure (Robain et al, 1996;Lebourg et al, 1999;Ritz et al, 1999;Jongmans et al, 2000;Sumanovac and Weisser, 2001;Lebourg and Frappa, 2001;Godio and Bottino, 2001;Wise et al, 2003;Perrone et al, 2004;Lebourg et al, 2005;Rey et al, 2006;Godio et al, 2006;Sumanovac, 2006). However, this method has been rarely used on deep seated landslides because of logistical difficulties with using resistivity equipment in steep and unstable terrain.…”

Section: Introductionmentioning

confidence: 99%

Identification of the gravitational boundary in weathered gneiss by geophysical survey: La Clapière landslide (France)

Jomard

Lebourg

Tric

2007

Journal of Applied Geophysics

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“…Although various geophysical techniques are currently being used to explore and assess water resources (e.g. the gravity method (ALI and WHITE- LEY, 1981), the seismic method (GEISSLER, 1989), the electromagnetic ground conductivity method (PALACKY et al, 1981;VAN LISSA et al, 1987), the geoelectrical section method (STEWART et al, 1983), resistivity imaging methods (IOANNIS et al, 2002), conventional VLF and VLF resistivity methods (PODDAR and RATHOR, 1983); electrical and magnetotelluric surveys (QUARTO and SCHIAVONE, 1994), and electrical resistivity tomography (RITZ et al, 1999)), the electrical resistivity method still proves the most powerful. We selected this method for our research because the instrumentation is portable, inexpensive in terms of logistics, straightforward, analysis of the data is less tedious and is economical (ZOHDY et al, 1974;EKINE and OSOBONYE, 1996;AKO and OLORUNFEMI, 1989;BATTE et al, 2008).…”

Section: Methodsmentioning

confidence: 99%

Correlation of Geoelectric Data with Aquifer Parameters to Delineate the Groundwater Potential of Hard rock Terrain in Central Uganda

Batte

Barifaijo

Kiberu

et al. 2010

Pure Appl. Geophys.

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Knowledge of aquifer parameters is essential for management of groundwater resources. Conventionally, these parameters are estimated through pumping tests carried out on water wells. This paper presents a study that was conducted in three villages (Tumba, Kabazi, and Ndaiga) of Nakasongola District, central Uganda to investigate the hydrogeological characteristics of the basement aquifers. Our objective was to correlate surface resistivity data with aquifer properties in order to reveal the groundwater potential in the district. Existing electrical resistivity and borehole data from 20 villages in Nakasongola District were used to correlate the aquifer apparent resistivity (q e ) with its hydraulic conductivity (K e ), and aquifer transverse resistance (TR) with its transmissivity (T e ). K e was found to be related to q e by; Log ðK e Þ ¼ À0:002q e þ 2:692. Similarly, TR was found to be related to T by; TR ¼ À0:07T e þ 2260. Using these expressions, aquifer parameters (T c and K c ) were extrapolated from measurements obtained from surface resistivity surveys. Our results show very low resistivities for the presumed water-bearing aquifer zones, possibly because of deteriorating quality of the groundwater and their packing and grain size. Drilling at the preferred VES spots was conducted before the pumping tests to reveal the aquifer characteristics. Aquifer parameters (T o and K o ) as obtained from pumping tests gave values (29,424.7 m 2 /day, 374.3 m/day), (9,801.1 m 2 /day, 437.0 m/day), (31,852.4 m 2 /day, 392.9 m/day). The estimated aquifer parameter (T c and K c ) when extrapolated from surface geoelectrical data gave (7,142.9 m 2 /day, 381.9 m/ day), (28,200.0 m 2 /day, 463.4 m/day), (19,428.6 m 2 /day, 459.2 m/ day) for Tumba, Kabazi, and Ndaiga villages, respectively. Interestingly, the similarity between the K c and K o pairs was not significantly different. We observed no significant relationships between the T c and T o pairs . The root mean square errors were estimated to be 18,159 m 2 /day and 41.4 m/day.

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Electrical imaging of lateritic weathering mantles over granitic and metamorphic basement of eastern Senegal, West Africa

Cited by 60 publications

References 9 publications

A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys

A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys

Identification of the gravitational boundary in weathered gneiss by geophysical survey: La Clapière landslide (France)

Correlation of Geoelectric Data with Aquifer Parameters to Delineate the Groundwater Potential of Hard rock Terrain in Central Uganda

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