Combining Electrical Resistivity Tomography and Ground Penetrating Radar to study geological structuring of karst Unsaturated Zone

This paper highlights the efficiency and complementarity of a light package of geophysical techniques to study the structure of karst Unsaturated Zone (UZ) in typical Mediterranean environment where soil cover is thin or absent. Both selected techniques, 2D Ground Penetrating Radar (GPR) and Electri...

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Bibliographic Details
Published in:Journal of applied geophysics 2013-07, Vol.94, p.31-41
Main Authors: Carrière, Simon D., Chalikakis, Konstantinos, Sénéchal, Guy, Danquigny, Charles, Emblanch, Christophe
Format: Article
Language:English
Subjects:
Electrical resistivity
Electrical Resistivity Tomography
Environmental Sciences
Geology
Geophysics
Ground Penetrating Radar
Hydrogeophysics
Karst
Karst near surface features
LSBB
Stratification
Underground
Unsaturated
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Summary:This paper highlights the efficiency and complementarity of a light package of geophysical techniques to study the structure of karst Unsaturated Zone (UZ) in typical Mediterranean environment where soil cover is thin or absent. Both selected techniques, 2D Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT), are widely used in environmental studies and their application is accessible for a lot of scientists/engineers. However, GPR or ERT alone is not able to provide an enhanced characterization of geological features in karst media. In the present study, GPR results supply a near surface high resolution imaging and thus can provide relevant geological information such as stratifications and fractures. Despite the quality of the results GPR's investigation depth remains limited to around 12m. Apparent and inverted resistivity provided by ERT surveys shows strong lateral and vertical variations. These variations can inform about general geological structuring and feature orientation. ERT is able to prospect down to 40m but it's a low resolution integrative technique. In the study area the investigated limestone is a commonly electrical resistive formation (more than 2000Ω.m). However deeper than 5–7m, the ERT profiles reveal several zones of moderate resistivity (around 900Ω.m). In these zones a stratification change corresponding to slanted bedding is clearly identified by GPR results. The combination of both GPR and ERT results can allow a well-established geological interpretation. These moderate resistivity zones with slanted beddings can explain the presence of a perennial water flow point 35m below the surface of the studied site within the underground gallery of the Low-Noise Underground Laboratory (LSBB). •Complementarities of GPR and ERT to image karst near surface features•GPR provides relevant geological information such as stratifications and fractures•GPR detect stratification changes in accordance with ERT profiles results
ISSN:0926-9851
1879-1859
DOI:10.1016/j.jappgeo.2013.03.014