GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 The Amplification Factors (AF) were calculated with LSR2D code along the sections every 30-50 m and with 3 calculated points located in a zone of 70 m, as a minimum, and 120 m, as a maximum. After the calculation of AFs, a 3-data filtering was performed to make the trend of the AF values homogeneous along the progressives of the section (Fig. 2). Since 2D simulations have been performed for each microzone, more points are available in which the AFs have been calculated. Therefore, based on an evaluation in favour of safety and subject to expert judgment, the AF of the microzone is the highest of those calculated within the microzones for the period interval 0.1-0.5 s and the accelerograms and response spectra representative of the microzone refer to those of the AF attributed to it. To evaluate the reliability of the calculated AFs, a quality control was performed by comparing the AFs with the geological and the first level SM maps. Indeed, it has been noted that the distribution of the calculated AFs is congruent with the geological background. In fact, along the sections a rough correspondence between the boundaries of the AF classes with the geological units is observed. Further, for the outcropping geological units, the AF values vary within a narrow range. It has been also observed that the AF values are conditioned by the more superficial seismic impedance contrast. However, these observations agree with the theory (Kramer, 1996; Lanzo and Silvestri, 1999) and, therefore, lead us to believe that the AFs obtained with the simulations are to be considered reliable. Moreover, considering the good correlation between the AFs and the geological background, the boundaries of the third level SM microzones were areally extended, based on the geological unit boundaries, and via expert judgment (Pergalani et al., 2020). Furthermore, to verify the quality control of the simulations and to refine the local seismic behaviour, any 2D effects were analyzed by comparing the AFs obtained with the 1D simulation with those calculated with the 2D ones in the same site. In several cases, the 2D basin effects were detected, as the AFs calculated in the basin center with 1D modelling was lower than the AFs estimated with 2D one (Fig. 2). Furthermore, near the slope break between the reliefs and the Aterno R. plain, the AF values calculated with 2D simulation are higher with respect to those 2D-estimated in the surrounding areas and are lower than those estimated with 1D modelling. This behaviour would probably be attributable to 2D basin edge effect (Lanzo and Silvestri, 1999) (Fig. 2). For almost all the sections of the Bazzano-Monticchio area crossing the Aterno R. plain, the AF values increase for the intervals of the higher periods, i.e., a shift of the seismic energy towards higher periods is noted (lower frequencies). This behaviour seems to be linked to 2D effect because the FAs calculated in points located on the Aterno R. plain with a 1D modelling are generally lower than the FAs estimated with the 2D one (Kramer, 1996). Finally, for some microzones not covered by 2D simulations, 1D ones were performed with LSR2D and Strata code (Kottke and Rathje, 2009). Soil liquefaction potential evaluation