GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.2 GNGTS 2024 CorrelaHon between site effects proxies: the case of Argostoli basin (Greece) D. Ajolico 1,2 , G. Cultrera 1 , V. De Rubeis 1 , N. Theodoulidis 1 1 Is9tuto Nazionale di Geofisica e Vulcanologia (INGV, Italy) 2 Asset - Agenzia regionale Strategica per lo Sviluppo Ecosostenibile del Territorio (Regione Puglia, Italy) The purpose of this work is to explore the potenCal of mulCvariate staCsCcal analysis method to define possible correlaCons between site response properCes. The considered data are seismological instrumental observaCons and geological-geophysical parameters that could be used as proxy for the characterizaCon of local site effect wherever seismological observaCons are not available. The study area is the Argostoli basin (Greece), chosen for both the amount of earthquake and seismic noise recordings, and the geological and geophysical available informaCon (Figure 1). We follow the approach of Abolico et al. (2022) where mulCvariate staCsCcal analysis was used to evaluate the most important site effect indicators and to deduce how the geological context influences their behaviours. The staCsCcal Factor Analysis technique has been applied to the different available or computed parameters including Horizontal-to-VerCcal spectral raCos on earthquakes (HVSR) and noise (HVNSR), averaged over 4 frequency intervals (see Cultrera et al., 2014, for further details), the predominant frequency of HVSR and corresponding amplitude, maximum duraCon lengthening value (calculated from the frequency dependent mean group delay of the Fourier spectrum phases, as proposed by Sawada, 1998) and the corresponding frequency; thicknesses of the 3 lithological contrasts idenCfied inside the basin; Vs average within the 3 aforemenConed thicknesses (from Cushing et al., 2020); PGA normalized to magnitude and hypocentral distance; depth of seismic events. The findings of this study suggest that the staCsCcal variaCon of ground moCon is influenced by the locaCon of the seismic staCons around and inside the basin, and by the type of lithology present underneath the site. AddiConally, duraCon lengthening parameter is strictly correlated with the basin morphology and it is a useful tool to describe the seismic moCon prolongaCon esCmaCon for the site effects studies.