GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 In this study, 36 sites were examined in the Preturo-Sassa area and 5 in the Bazzano-Monticchio area for assessing the soil liquefaction potential. Most of the sites (where shear wave velocity data were available) were classified in subsoil category C, with an equivalent shear wave velocity, Vs,eq, between 180 m/s and 360 m/s. The results of the simplified analysis based on empirical charts lead to zero or low level of Liquefaction Potential Index, LPI (Iwasaki et al., 1984), except for the Pagliare di Sassa site (moderate level) (Fig. 1). In the examinated pilot areas, this result is due to the absence of factors predisposing to liquefaction, such as conditions of complete saturation and loose granular soils, while a secondary role is probably played by the triggering action (i.e., the seismic action). Therefore, the uncertainties related to the determination of the seismic demand, such as the simplifying assumption about the magnitude and the adoption of a single seismic scenario, do not affect the results of the study for the above-mentioned reasons. The zero/low liquefaction potential obtained from the simplified approaches did not make it necessary to use more sophisticated methods of analysis, such as simplified and advanced dynamic analyses (Chiaradonna, 2020). The third level SM deliverables The following documents have been produced for the Preturo-Sassa and Bazzano-Monticchio areas (L’Aquila Municipality): (i) third level SM maps of the AFs for the three period intervals (0.1-0.5 s, 0.4-0.8 s, 0.7-1.1 s) at 1:5000 scale; (ii) database organized by using the CNR-IGAG plugin "MzS Tools" operating on QGIS ver. 3.22 (Cosentino and Pennica, 2022). For each microzone, the following data were also produced: (i) n. 3 AFs, one for each period interval; (ii) n. 7 natural accelerograms used as seismic input for the 2D modelling; (iii) n. 7 elastic acceleration response spectra at 5% damping (output spectra) at the surface, one for each input accelerogram; (iv) the representative output spectrum of the microzone, i.e., the average spectrum of the 7 above mentioned spectra; (v) the Vs,eq value and the related subsoil category according to NTC 2018. The Vs,eq value was calculated, for each microzone, using the average thickness of the seismolayers and the relative values of Vs used for the modelling. Conclusion Considering the complex seismostratigraphy of L'Aquila territory, 2D modeling was carried out on a very large number of sections (n. 15) to calculate in-depth the AFs and analyze their areal variation. The validity of 2D modelling was confirmed by the congruence between the geological background and the AFs value distribution. Finally, 2D modelling allowed to verify the existence of basin and basin edge effects via the comparison with 1D simulations.