GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 3.2 631 flooring, can be estimated as made by coarse and aerated material having a modest thickness (about 0.80 m). It was also possible to detect the existence of a crypt located underneath the main altar (Fig. 3a). The scanned section sets indeed into evidence the existence of a rectangular shape anomaly (4.0 x 2.5 m) having a barrel vault with the highest point located at about 45 cm from flooring level. The crypt floor is instead located at about 3 m depth. In the neighboring the existence of some reflectors, probably corresponding to some recesses or to the entry tunnel, were observed. The depth-slice shown in Fig. 3b points out, in correspondence of the main entrance of the church, the presence of a further reflector, having a squared shape, probably linked to the existence in the subsoil of wall ruins belonging to the old edifice. The findings obtained through the tomographic tests (Fig. 3c) set into evidence the presence of low seismic velocities (450-600 m/s) in the shallower layers, so that it is possible to infer the existence of a detritus layer, underneath the floor, having thickness of about 1 m. It is interesting to point out that the continuity of the shallow detected low velocity layer appears locally interrupted by small areas showing a velocity increment (800-900 m/s) (Fig. 3c), probably linked to the presence of man-made structures of the ancient edifice. It is finally interesting to set into evidence that both the adopted methodologic approaches pointed out the presence of important anomalies in the measured geophysical fields. The comparison and the mutual validation of the obtained findings allowed us to infer a suitable interpretation. Acknowledgements This paper was carried out with the financial support of the University of Catania (Convenzione Commesse Interne, Scientific Supervisor: S. Imposa). The authors are grateful to Ing. Scandurra Giuseppe for providing the architectural drawings of the church. References Barilaro D., Branca C., Gresta S., Imposa S., Leone A., Majolino D.; 2007: Ground penetrating radar (GPR) surveys applied to the research of crypts in San Sebastiano’s church in Catania (Sicily) . Journal of Cultural Heritage, 8(1), 73-76. Costarelli N.; 2005: La Chiesa Parrocchiale “San Michele Arcangelo” di Acireale nella Diocesi omonima: Storia, cultura e tradizioni, dalle origini agli albori del nuovo millennio Davis J.L., Annan A.P.; 1989: Ground-penetrating radar for high-resolution mapping of soil and rock stratigraphy . Geophysical Prospecting, 37, 531-551. Forte E. and Pipan, M.; 2008: Integrated seismic tomography and ground-penetrating radar GPR for the high- resolution study of burial mounds tumuli.  Journal of Archaeological Science, 359, 2614-2623.  doi.org/10.1016/ j.jas.2008.04.024 Goodman D. and Piro S.; 2013: GPR Remote Sensing in Archaeology . Springer Berlin Heidelberg. Gresta S., Bella D., Musumeci C., Carveni P.: 1997: Some efforts on active faulting processes (earthquakes and aseismic creep) acting on the eastern flank of Mt. Etna (Sicily) . Acta Vulcanol., 9 (1–2), 101–108. Imposa S. and Lombardo G.; 1985: The Etna earthquake of February 20, 1818 . In: CNR P.F. Geodinamica Gruppo Catalogo Dei Terremoti. (a cura di): D. Postpischl, Atlas of isoseismal maps of Italian earthquakes, Quaderni de “La Ricerca Scientifica”, D. Postpischl (Editor). vol. 114, 2A, p. 80-81, Roma: GTM Imposa S. and Mele G.; 2011: Ground penetrating radar survey inside the S. Agata cathedral of Catania (eastern Sicily).  International Journal of Architectural Heritage, 5(2), 188-197. Imposa S. and Grassi S.; 2015: Georadar survey inside the Santa Maria Maggiore church of Ispica (Sicily- Italy). Environmental Earth Sciences, 73(5), 1939-1949. IDS Ingegneria Dei sistemi S.p.A.; 2009: Software Gred elaborazione dati Georadar ISPRA-Servizio Geologico d’Italia; 2009 : F 625 Acireale , scala 1: 50.000. Optim L.L.C.; 2003: SeisOpt ReMi v2.0 forWindows 95/98/00/NT/Me/XP , Optim Software and Data Services, UNR- MS-174, 1664 N. Virginia St., Reno, Nevada. 89557. Pullammanappallil S.K. and Louie J.N.; 1994: A generalized simulated-annealing optimization for inversion of first- arrival times . Seismological laboratory (174), Mackay school of mines, university of Nevada, Reno. Bull. Soc. Seism. Am. 84 (5), 1397–1409. Vafidis A., Manakou M., Kritikakis G., Voganatsis D., Sarris A., Kalpaxis T.; 2003: Mapping the ancient port at the archaeological site of Itanos Greece using shallow seismic methods . Archaeological Prospection, 103, 163-173. doi: 10.1002/arp.212