GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 3.2 669 well, including many diffractions at shallow depth and several deeper high amplitude reflectors of good continuity (Fig. 2b). Results and Conclusion. The interpretation and mapping of the GPR anomalies has allowed us to improve the knowledge of unknown buried structures in the subsurface of an ancient urban area (Silvani, 2019). The preliminary results show three main intervals of GPR reflections, that we classified in base of their depth. The shallower features, mainly small diffractions, can be correlated with the network of utilities located within the first meter depth. The intermediate and deeper targets identified in the interval 1-4 meters, represented by wide diffractions and relatively continuous reflections, have been interpreted as voids or roofs of unknown buried chambers/tunnels. The data analysis suggests two main alignments of the deeper GPR anomalies, interpretable as possible paths of the tunnel inferred during the survey planning (Fig. 3). According to the geomorphological arrangement and in detail to the morphology and the groundwater circulation, two hypotheses may be advanced. For the path with a WNW direction the tunnel may be parallel to an ancient road (etruscan and roman) whose remains have been found in several parts of the historic center; our GPR data interpretation may suggest its path continuing along the Piccinino square. On the other hand, the second possible path in NW-direction seems to follow the direction of the underground drainage network, moving the water from the top of the hill toward the headwater of the rivers flowing toward N and NE. In the old town similar examples have been already reported: their role was the water drainage from the fluvial and lacustrine sediments and therefore the improvement of the slope stability of the area. The complete analysis of the available pseudo- 3D dataset, as well as further GPR data acquisition through densely spaced 3D GPR volumes, will possibly solve the current interpretation uncertainties. Nevertheless, these results confirm the GPR as a powerful geophysical tool for the discovery of buried unmapped structures. Our multidisciplinary approach integrating archaeology, geomorphology and geophysics represents the best solution to detect underground remains in historical urban areas. Acknowledgments. This research was funded by the Dipartimento di Fisica e Geologia, Universita degli Studi di Perugia, project title “PERUSIAE (PERUgia StratIgraphy, geoArcheology and landscapE): a multidisciplinary reappraisal of the geological assessment of Perugia Hill)”, RicBAs2014, awarded to Laura Melelli and by the project title “HUSH UNDERGROUND - Hiking in Urban Scientific Heritage. Augmented Reality for the hidden cavities of Perugia (Umbria, central Italy)”, RicBAs2017 awarded to Laura Melelli. References Bizzarri R., Melelli L., Cencetti C.; 2018: Archaeo-geosites in urban areas: a case study of the Etruscan Palazzone Necropolis (Perugia, central Italy) . AIQUA (Alpine and Mediterranean Quaternary), 31(2), 207-219. Ercoli, M., Pauselli, C., Forte, E., Di Matteo, L., Mazzocca, M., Frigeri, A., Federico, C.; 2012: A multidisciplinary geological and geophysical approach to define structural and hydrogeological implications of the Molinaccio spring (Spello, Italy), Journal of Applied Geophysics, 77, 72–82. Ercoli, M., Brigante, R., Radicioni, F., Pauselli, C., Mazzocca, M., Centi, G., Stoppini, A.; 2016: Inside the polygonal walls of Amelia (Central Italy): A multidisciplinary data integration, encompassing geodetic monitoring and geophysical prospections , Journal of Applied Geophysics, 127, 31-44. Gregori, L., Melelli, L., Rapicetta, S., & Taramelli, A.; 2005: The main geomorphosites in Umbria. Il Quaternario Italian Journal of Quaternary Sciences , 18(1), 91-99. Jol H.M; 2009: Ground Penetrating Radar: Theory and Applications , Elsevier Melelli, L., Bizzarri, R., Baldanza, A., & Gregori, L.; 2016: The Etruscan “Volumni Hypogeum” Archeo-Geosite: new sedimentological and geomorphological insights on the Tombal complex. Geoheritage, 8(4), 301-314. Melelli, L.; 2019: “Perugia Upside-Down”: A Multimedia Exhibition in Umbria (Central Italy) for Improving Geoheritage and Geotourism in Urban Areas . Resources, 8(3), 148. Silvani, F.; 2019: Geoarcheologia del centro storico perugino: approcci geomorfologici, geomatici e geofisici per lo studio di strutture ipogee connesse al Pozzo etrusco. Corso di Laurea in Geologia. Tesi di Laurea Triennale, Università degli Studi di Perugia, A.A. 2018-2019. Relatori: Dott. Maurizio Ercoli, Dott.ssa Laura Melelli. Stopponi, S.; 1973: Il Pozzo Sorbello in Perugia. Quaderni dell’Istituto di Archeologia di Perugia, 2, 191 pp. Stopponi, S.; 1991: Nuove osservazioni sul Pozzo Sorbello e sul suo inserimento nel tessuto storico di Perugia. In: Bergamini S. “Gli Etruschi maestri di idraulica”, Mondadori Electa Ed., Milano, 235-246.