GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 Within the third level SM project, the previous elaborated first level SM database was updated with new ad hoc investigations that were placed in remarkable sites of the pilot areas. Given the complex seismostratigraphy of middle Aterno River basin, characterized by a thick and complex sedimentary sequence, four 2D seismic arrays were performed which permitted to obtain the Vs profile up to great depths reaching the Meso-Cenozoic calcareous-terrigenous substratum. For the estimation of the soil liquefaction potential, specific in-situ investigations (CPTU and SDMT tests) were also carried out in pivotal sites. In this case, particular attention was paid to the selection of sites which were considered potentially liquefiable based on geological and hydrogeological observations. Following the Italian technical standards for construction NTC18 (CS.LL.PP ., 2018), seven natural accelerograms were selected as seismic inputs and were used in the numerical simulations for the estimation of the Amplification Factors (AF). The online database used for the selection of the septuple is REXELite which is available at the link: DYNA-stage - REXELite [Cadmo v3.1690 page=REX_rexel_homepage] ( ingv.it ). REXELite is the simplified version of the Rexel database (Iervolino et al., 2009). To have a rational balance between the analysis accuracy and the computational burden, able to consider the non-linear behaviour of soil, the local seismic effects, and the geological complexity of middle Aterno River basin, it was decided to resort to the 2D equivalent linear modelling. Based on these considerations, for the AFs evaluation, LSR2D code by software house Stacec s.r.l. (https://www.stacec.com/lsr-2d_pp92.aspx) was used. LSR2D performs the 2D equivalent linear modelling by using the finite element approach, in the time domain and in total stresses, and the Kelvin-Voigt model. Geological sections and geophysical & geotechnical soil characterization Many geological sections (n. 15) were elaborated and 2D simulations were carried out. The sections were traced to cross most of the SM microzones of the pilot areas and the most significant geological boundaries (fault contacts, alluvial terrace scarps, landslides, anthropic deposits, etc.). Moreover, the sections were located close to the geophysical investigations (microtremor measurements and down-hole tests) and boreholes to better constrain the subsoil model (Fig. 1). They start and end at least 400 m outside the extremes of the section almost always located in the seismic bedrock, so to minimize in the simulations the edge phenomena due to the lateral dispersion of the seismic energy (Fig. 2). Orthogonal sections have also been elaborated for checking with the simulations possible 2D phenomena due to seismic directionality. The seismolayers were characterized considering the geophysical (Vs, Poisson's ratio) and geotechnical (density, G/G 0 - γ decay and D- γ damping curves) parameters starting from many studies on seismic site characterization and seismic ground response of L’Aquila area (Macerola et al., 2019 and references therein). Numerical modelling