Aplicación del método electromagnético de inducción ligera para el análisis de la permeabilidad en medios fracturados (granito de "El Berrocal", Sistema Central Español) Application of the low-induction electromagnetic method for the permeability analysis in fractured rocks («El Berrocal» granite, Spanish Central System)

Fracture characterization in granites has been an important subject of study during these last years, by means of geological-structural cartography, hydrogeology and geochemical analysis. These works have been carried out to investigate the hydromechanics and permeability in low-permeability rocks. In this study we apply a surface geophysical method in order to characterize the permeability of the fault zones affecting «El Berrocal» granite (Central System, Spain). The low-induction electromagnetic method (EM) gives us the apparent resistivity (ρ a ) values of the rocks at a maximum depth. As the ρ a depends on the granite alteration and/or the water content, this parameter allows estimating the relative permeability of different fracture zones. The obtained results show that the high-permeability fractures are those that are larger ones which were active during Alpine deformation (Eocene-present).