Théorie de l'électrofiltration: nouveaux développements, validation expérimentale et applications à l'hydrogéologie et au volcanisme.

The self-potential method consists on the passive measurement of the electrical potential distribution at the ground surface of the Earth. This is the only method that is sensitive to the flow of the ground water. The main objectives of this work were (1) to determine the influence of the surface conductivity and the flow regime upon the streaming coupling<br />coefficient (a critical parameter to interpret SP signals), (2) to show the efficiency of the SP in the localization of hydromechanical disturbances, (3) to characterize ground water flow and aquifers in a volcanic context. For indifferent electrolytes, like sodium chloride, we derived two simple scaling laws for the dependence of the streaming potential coupling coefficient with the surface conductivity and Reynolds number. The validity of these laws was checked successfully against a new set of experimental data using glass bead. In sandbox experiments, the self-potential method associated with a high sensitivity equipment has enabled us to characterize the electrostatic signature of hydromechanical disturbances. The wavelet analysis and the cross-correlation method showed the dipolar nature of the electrical source linked to such disturbances and can be used to locate the source. On Stromboli in Italy, we used a relationship between the thickness of the vadose zone and the self-potential anomaly to determine the shape of the water table along the flank of the volcano.