Evaluation of the local seismic response in the area of Catania (Italy)

Site response evaluation in Catania was performed in test areas potentially suffering local amplifications of the ground motion. The local seismic response was evaluated through spectral ratio techniques taking the horizontal-to-vertical component ratio of ambient noise. Inference from microtremor measurements are compared with results from synthetic accelerograms and response spectra computed using all available drillings for this area. The microtremor H/V spectral ratios evaluated at soft sites, located within the downtown profile, tend to be smaller than that usually reported in the literature for such soils. A tendency for amplifications to peaks near 2 Hz is observed only in some sites located on recent alluvial deposits. Evidence for amplifications of site effects were observed nearby a fault, with a tendency towards a decrement of spectral amplitudes at increasing distance from the discontinuity. Results confirm the importance of knowing the shallow stratigraphic sequence in the estimate of local hazard scenarios.