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Abstract:
Estimation of amplification factors (AFs) at the local or regional scale is an important task in land planning and seismic design, especially in areas with high seismic hazards and complex geological and geomorphological structures of the territory, such as Italy. When multiple seismic recordings at a single site are available, they can be exploited to estimate AFs empirically through many methods, such as: a) spectral ratios between i) the horizontal and vertical ground-motion components and ii) the shaking observed at the site and at a reference rock site, both for acceleration response and Fourier spectra; b) parametric or non-parametric generalized spectral inversion techniques; and c) decomposition of residuals of a nonergodic Ground Motion Model (Rodriguez-Marek et al., 2011; Priolo et al., 2020, among the others) to estimate repeatable within-site terms (δS2S). In this study, we exploited the estimates of δS2S provided by Lanzano et al (2022), through the ITACA (ITalian ACcelerometric Archive) web portal (https://itaca.mi.ingv.it/ItacaNet_32/#/products/itacas2s_flatfile), to compute the AFs for about 800 recording sites in Italy. We then compare AFs estimates with different proxies for predicting the site effects, such as Vs profile, resonance frequency, cover geology and topographic slope. Moreover, we also employed the empirical AFs to validate the estimates provided by 1D, 2D and 3D numerical modeling of the site response. Later, we investigate spatial correlation of the AFs in urban areas, where dense networks are installed.
