Borehole seismic surveys for the mechanical and seismic characterization of a calcareous cliff in the area of Ispica (southeastern Sicily)

The purpose of this work is to characterize the mechanical and seismic structure andthe seismic response of a cliff occurring on Miocene calcarenite in the area of Ispica, insoutheastern Sicily. The cliff face oriented NE-SW represents one of the faultescarpments of the regional Pozzallo-Ispica-Rosolini fault system. On the top of thecliff is a convent of Friars Minor, built in the XVI century, whose floor recently showedsigns of fracturing. In this study, we have used three 30-m drillings excavated during aprevious survey to carry out down-hole tests (DHT) and seismic tomography in upholeconfiguration. Down-hole tests provided point measurements of P and S wave velocityfrom which we have computed elasto-dynamic and seismic parameters, while seismictomography enabled to image the P-wave velocity across the cliff. The results allowedto distinguish four seismic layers correlated with the different degree of fracturing in thecalcarenite, and highlighted the presence of secondary ruptures parallel to the mainfault escarpment. We have also recorded the ambient noise at five stations deployedalong a profile perpendicular to the cliff's edge, but no significant amplification wasobserved.