GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 3.2 621 CROSS-VALIDATION OF MULTISOURCE ERT MEASUREMENTS VIA CONTINUOUS POTENTIAL MONITORING. AN EXPERIMENT IN THE VAJONT VALLEY (NORTH-EASTERN ITALY) F. Bocchia 1 , R.G. Francese 1,2 , M. Giorgi 2 , F. Fischanger 3 , S. Picotti 2 1 Department SCVSA, University of Parma, Italy 2 National Institute of Oceanography and of Experimental Geophysics – OGS, Trieste, Italy 3 Geostudi Astier S.r.l., Italy Introduction and motivations. The MultiSource Wireless Resistivity System (MS) is a recent technological achievement and it has already been used for imaging deep (LaBrecque et al. , 2013a; 2013b) and shallow targets (Picotti et al. , 2019) in various geological environments. The existing contributions, available in the literature, mostly describe case studies in the fields of geothermal exploration, landslide and glacier imaging but little information is available on the potentials and limitations of the system itself. The MS resistivity system (LaBrecque et al. , 2013b) takes full advantage of the availability of wireless data communication and GPS modules capable of performing precise real time synchronization and positioning. These systems of distributed transmitters and receivers are much easier to deploy overcoming the most common logistical problems (topography and geography) in all those cases when the multicore cable is barely usable. The present contribution addresses the analysis of the intensity of the MultiSource signal at medium at large offset using an array of passive potential receivers in controlled geological conditions. Fig. 1 - Site map and deployment. The experiment. The experiment was carried out on the left side of the Vajont valley in north-eastern Italy, nearby the dam and right on the top of the 1963 landslide (Fig. 1). The site was selected because it has been studied since a long time ago and because of the availability of several independent geophysical datasets (2D and 3D seismic imaging, standard and novel concept resistivity surveys, borehole logs, etc). Some of these data have been collected in the late sixties of the last century (Morelli et al. , 1965) while several others were collected few years ago (Bistacchi et al. , 2013; Francese et al. , 2013; Bohm et al. , 2014), within the framework of an international research project, for the 50-years anniversary of the Vajont disaster.