GNGTS 2017 - 36° Convegno Nazionale

614 GNGTS 2017 S essione 3.2 model. The two proposed correlation parameters (Figs. 3d and 3e) are able to differentiate with greater precision the cavity (values ​close to 0) from the high compact rock (high values), except for the cavity positioned at the end of acquisition line, due to the low resolution of the data in this area. Finally the results of a non-hierarchical cluster analysis algorithm for a number of clusters equal to 5 are showed (Fig. 3f). Conclusions. The study of synthetic and models of experimental data has shown that the integrated study of the seismic refraction tomography and electrical resistivity tomography is the most suitable approach for the detection of cavities in the subsoil, as it is able to minimize the possible interpretation ambiguities. The cluster analysis performed on static units defined by electrical resistivity values, P wave velocities, and seismic density on coincident sections, allowed to interpret subsoil structures. The use of the non-hierarchical clustering algorithm has been chosen because it is less influenced by abnormal values, and allows a statistical unit to change its cluster during the iterative process. Depending on the choice of the number of clusters to be identified, cluster distribution maps have been constructed in the multi-parameter space, allowing defining certain variability limits for the selected parameters, for synthetic and experimental data. Finally, experimental data show that electrical and seismic tomographies is not influenced by the presence of cavities without lateral continuity. References Capizzi, P., Cosentino, P.L., Fiandaca, G., Martoran,a R., Messina, P. [2005] 2D GPR and geoelectrical modelling: tests on man–made tunnels and cavities. 11th European Meeting of Environmental and Engineering Geophysics of the Near Surface Geoscience Division of the EAGE, Near Surface 2005; Palermo; Code 104313, B036 1-4, ISBN 90-737-8191-4. Cardarelli, E., Fischanger, F., Piro, S. [2008] Integrated geophysical survey to detect buried structures for archaeological prospecting. A case-history at Sabine Necropolis (Rome, Italy). Near Surface Geophysics 6, 15–20. Cardarelli, E., Cercato, M., Cerreto, A., Di Filippo, G. [2010]. Electrical resistivity and seismic refraction tomography to detect buried cavities. European Association of Geoscientists & Engineers. Geophysical Prospecting, 2010, 58. 685-695. Fasani, G.B., Bozzano, F., Cardarelli, E., Cercato, M. [2013] Underground cavity investigation within the city of Rome (Italy): A multi-disciplinary approach combining geological and geophysical data. Engineering Geology 152. 109-121. Gallardo, L. A. and Meju, M. A. [2004] Joint two-dimensional DC Resistivity and Seismic travel time inversion with cross-gradients constraints, Journal of Geophysical Research, 109, doi:10.1029/2003JB002716. Fig. 3 - Seismic rays density d (a), P-waves velocity V P (b), electrical resistivity model (c), two correlation parameters (d and e) and cluster distribution (f) for experimental data.