High frequency strong ground motion modelling in the Catania area associated with the Ibleo-Maltese fault system

A hybrid statistical-deterministic approach has been applied to estimate st rong ground motion parameters (PGA, spectral ordinates) in South-Eastern Si cily for a M = 7 earthquake. A number of 100 different rupture processes ha ve been simulated along a composite fault system representing two segments of the Ibleo-Maltese fault scarp. Map at regional scale of mean PGA in the 0.5-20 Hz frequency band shows highest values (0.4-0.5 g) nearby and North of Catania, due to a dominant directivity effect. The COV parameter, which expresses the variability of PGA values as a function of source complexity, is higher in the region nearby and South of the town of Augusta, where, de pending on the rupture history, rather large PGA values can be observed (> 0.4 g). PGA attenuation curves suggest that an azimuthal variation could be related to the source extent and directivity. The response and pseudo acce leration spectra are computed for different sites in the town of Catania in cluding an approximate 1D site response. Ground motion amplification effect s at high frequency (5-20 Hz) are produced by thin shallow layer of soft cl ay, loose pyroclastites and fill. We observe small amplification effects, i n the frequency ranges 2-3 Hz and 5-10 Hz, in sites where recent alluvia re ach a thickness of some tens of meters. Otherwise, sites located on outcrop s of massive lavas show moderate attenuation.