GNGTS 2021 - Atti del 39° Convegno Nazionale

335 GNGTS 2021 S essione 2.2 very hard-rock sites is poor, the upper bound of the V S30 scaling, corresponding to 1500 m/s, abo- ve which the amplification is independent on V S30 according to [Kamai et al. 2014]. The function is linearly dependent on V S30 , consistently with the ITA18 horizontal model. As regards the uncertainty treatment, the standard deviations of the predicted vertical ground motion are computed from the error propagation of the horizontal and VH models. In Figure 2, the predictions of vertical SA(0.1s), left, and SA(1.0s), right, from the ITA18 model (i.e. VH and H GMMs from this study and Lanzano et al., 2019, respectevely) are compared with Fig. 2 - Median (±σ) vertical SA(0.1s), left, and SA(1s), right, as a function of R JB , for M w 4.0 and M w 6.3 scenarios (top: NF; center: TF; bottom: SS) with V S 30 =450 m/s, against observations from ITA18 dataset (superimposed dots, V S 30 ± 100 m/s, M W ± 0.3).