Seismic property characterization of lithotypes cropping out in the Siracusa urban area, Italy

The town of Siracusa is located in the south-eastern coast of Sicily (southern Italy) in a wide inlet engraved into a limestone formation. This lithotype, which is overlaid by soft sediments such as sandy clays and detritus, can be considered as the local bedrock. Present study aims to investigate on the dynamic properties of main lithotypes outcropping in the study area and their relationships with the local seismic response. Non-invasive seismic prospecting techniques using the vertical component of surface waves (MASW and ReMi) were adopted, as well as ambient noise measurements, processed through the Nakamura technique. The best solution for the experimental dispersion curves was selected using the neighbourhood algorithm and information about the deeper part of the estimated shear wave profiles was obtained by considering the ellipticity of the fundamental peak. Moreover, a cluster analysis was performed to subdivide into homogeneous groups the experimental noise spectral ratios. Results obtained pointed out that the use of combined different methods provides a robust way to characterize the investigated soils and to reduce the problems linked to the non-uniqueness of solutions during the interpretation of geophysical data.

► MASW and ReMi techniques were used to detect the VS,30 features.
► Use of MASW and ReMi f–k plots reduced the doubts inherent to the source direction.
► Information about deeper part of the VS profiles was obtained using HVNR ellipticity.
► Use of cluster analysis allowed subdividing HVNR into groups showing a similar shape.
► Joint use of MASW, ReMi and HVNR, provides a robust way to characterize soils.