GNGTS 2022 - Atti del 40° Convegno Nazionale

240 GNGTS 2022 Sessione 2.1 An automatic algorithm is employed, which consists of removing the instrumental response and applying a Butterworth band-pass filter with high-pass magnitude dependent corner frequency: 0.08 Hz for magnitude above 6 to 0.3 for magnitudes between 3 and 6; and to 0.5 Hz for events smaller or equal to 3. A low pass corner frequency is fixed to 90% of the Nyquist frequency. The signal window is defined as the interval between the 2.5% and 97.5% percentile of the cumulative squared acceleration computed from the estimated P-wave arrival. We additionally applied signal-to-noise ratio (SNR) constraints and outlier detection to drop segments with the potential multiple-event signal and high-noise segments. Records with SNR smaller than 20 over the frequency range from 0.5 to 20 Hz are not further processed. The outlier detection is a modified Z-score method applied to the median absolute deviation of residuals. The residuals are with respect to predictions from Ground Motion Prediction Equations (GMPEs) considering the PGV and PGA for Europe and Middle East (Bindi et al., 2014) to detect the presence of outliers. The threshold is according to Iglewicz and Hoaglin (1993) that suggested the Z-score for the presence of outliers was greater than 3.5 or lower than -3.5. Method. We perform a spectral decomposition approach to characterize the FAS into source, propagation and site contributions. The generalized inversion technique (GIT) (Castro et al., 1990) is a well-knownmethod to derive frequency-dependent attenuation characteristics as well as source and site contributions. The FAS of ground motion can be written by the following system of linear equations: (1) We split the decomposition approach into two steps: first, we determine the attenuation models introducing a two domains regionalization. The regional attenuation models are Fig. 1 - Map with earthquake (circle sizes depending on the earthquake magnitudes) and station locations used in this study. Circles in blue represent tectonic events and in red represent induced events.