RISPOSTA SISMICA LOCALE 1D E 2D DI AREE PILOTA DEL COMUNE DELL’AQUILA NEL PROGETTO DI MICROZONAZIONE SISMICA DI TERZO LIVELLO

The topic of the research is the study of the local seismic response at sites with complex geologies. The opportunity to delve deeper into the topics covered by the research work, was achieved with participation in the activities relating to the study of seismic microzonation 3rd level of the urbanized and/or urbanizable territories of some sample areas of the municipality of L'Aquila and in the creation of geological investigations for the areas susceptible to instability, in which the University of L'Aquila is the protagonist. This activity took place within the framework of the agreement stipulated on 11/22/2018 between the Abruzzo Region (Department of Territorial Government and Environmental Policies - Civil Protection Risk Prevention Service) and the Department of Civil, Construction-Architecture and Environmental Engineering (DICEAA, University of L'Aquila) - reference period 2019-2023. The agreement was aimed at the study of the 1st and 3rd level MS of the areas of Preturo-Sassa and Bazzano-Monticchio and consisted in the creation of 3rd level MS maps in these areas and in updating and integrating those of 1st level developed within the scope of a previous agreement stipulated on 30/10/2012 between the Abruzzo Region (PPL Directorate, Integrated Cycle, Soil and Coastal Defence, Civil Protection – Risk Forecasting and Prevention Service) and the DICEAA. The activities of the convention were coordinated by prof. Marco Tallini (DICEAA). The doctoral work focused on subsurface modeling, 1D and 2D numerical simulations, and geophysical and geotechnical characterization of earthquakes. With specific reference to the characteristics of the areas under study, the presence of complex geomorphological conditions is highlighted, for which a 1D analysis is generally not sufficient: edge effects in alluvial valleys, presence of discontinuities (faults), topographic effects. Furthermore, it is highlighted that for the L'Aquila area there is a large campaign of experimental investigations which it is possible to compare and correlate the results of the analyzes (HVSR, Cross-Hole, laboratory tests (RC, CST)) and there are various studies, academic articles and publications which can be referred to for the geological/geotechnical framework and for the mechanical characterization of soils. To investigate any 2D effects, which is the objective of the research, comparisons were made on the same site of the FAs obtained with the 1D simulation with those calculated with the 2D simulation. From this point of view, it can be considered that the research had a satisfactory outcome, as in some areas "two-dimensional basin effects" were actually highlighted, as the FA calculated at the center of the basin with 1D modeling was lower than the estimated FA with 2D simulation. Furthermore, near the slope break between the surveyed area and the Aterno plain and its tributaries, there is a peak in the FA values with those estimated with 1D modeling almost always lower than those calculated with 2D simulation. This situation would probably be attributable to a "two-dimensional basin edge effect" (Lanzo & Silvestri, 1999). For almost all the sections of the Bazzano-Monticchio area that affect the Aterno river plain, the FA values increase for the intervals of the higher periods, i.e. there is a shift in seismic energy towards higher periods (lower frequencies ). This phenomenon seems to be linked to a two-dimensional effect because the FAs calculated at points located in the plane with a 1D modeling are generally lower than the 2D ones (Kramer, 1996). Finally, for some microzones not covered by the 2D simulations, 1D simulations were performed again with the LSR2D code and the Strata code (Kottke & Rathje, 2009).