Characterization of the subsoil in the area of the Friars Minor Convent of Ispica (Southeastern Sicily)

The main goal of this work has been the characterization of the subsoil beneath the convent of the Friars Minor of Ispica, a village located in southeastern Sicily. This building, located on top of a calcarenitic cliff, shows evidence of failure and instability. To achieve this target, we have estimated the Vs30 in three mechanical drillings using the down-hole technique (DHT) and carried out a seismic tomography survey. The present study complements previous geognostic and structural surveys published by Imposa et al. (2010). Considerable advancement has had, recently, the analysis of refraction data for the characterization of rocky terrains in terms of seismic waves velocity and amplitude, for the identification of deep interfaces and the determination of the degree of fracturing. The degree of fracturing in a medium affects the propagation of seismic waves: fractured volumes of rocks show lower P and S waves velocity, dispersion and attenuation, anisotropy of velocity (e.g., Abu-Zeid & Vuillermin, 1996); mapping Vs variations allows to infer variations of mechanical properties throughout the medium.