Résumé
In the Mediterranean Basin, most of the groundwater resources are located in carbonate aquifers. Inthe Montpellier area, southern France, several regional faults affecting these carbonate reservoirscontrol the location of the main flow paths and thus the groundwater flow. These faults zones arecharacterized by a strong anisotropy of permeability, sometimes induced by an offset betweencompartments on both sides of the fault. Fluid flow generally occurs preferentially in the fault-paralleldirection. Fractures located in the damaged zone of these faults, partly responsible for this anisotropy,are also at the origin of karst features development. Thus, to identify the main permeabilitycomponents of such fault zones, it is essential to identify- -(i) the structure of the damaged zone+ -(ii)the fault offset and, -(iii) the presence of karst features and their geometry. A methodology based onElectrical Resistivity Tomography (ERT) was thus proposed with this purpose. It allowed -(i) tohighlight en-echelon fracturing in the studied fault-zones+ -(ii) to identify the presence of karst featureand -(iii) to precise their geometry. Though the fault was a priori considered as a conduit-barrier, wedemonstrated that groundwater flow across the fault probably occurs due to the en echelon offset ofthe fractures and that karst features preferentially located along bedding planes control most of theflow.