Detailed imaging of tectonic structures by multiscale earth resistivity tomographies: the Colfiorito normal faults (Central Italy)

This study is aimed to show how cost effective geophysical surveying, integrated with detailed knowledge of the local geology, can give a significant contribution to image the subsurface structure of complex areas of active faulting. The combined inversion of a data set consisting of a large scale tomography and a target-dependent multiresolution dipole-dipole measurements, the multiscale approach, is shown to yield detailed structural information and to infer some characteristics of the fault zone. The operating procedure, applied to the Colfiorito fault system, allowed to differentiate the electrical signatures of the crossed faults. Minor faults show sharp lateral variations generated by a contact between different geological formations, while the major faults are also characterized by a decrease in resistivity values distributed on the fault damage zones. A close interpretation was supported by detailed geological surface data. Besides, quantitative correlations between in situ resistivity distribution and geological units were supported by electrical logs.