## 2 Site Investigations and Subsurface Model  
To develop the geotechnical model, the area was extensively investigated through a combination of 10 boreholes--one of which reached a depth of 90 m--along with 9 SDMT tests, standard penetration tests (SPT), and seismic ambient noise measurements. As previously described, the subsoil beneath the hill where the hospital and university complexes are located is highly complex. It consists of fine to coarse calcareous fragments of varying sizes--mostly a few centimetres--embedded in a sandy or silty matrix. This material is characterised by highly variable degrees of cementation and mechanical properties, with an overall deposit thickness of approximately 100 m. The planimetric location of the boreholes and the corresponding SDMT test locations (indicated as S) are illustrated in Figure 1.  
The results of previous investigations conducted as part of the seismic microzonation study were also utilised. All surveys carried out in the area confirmed the generally coarse-grained nature of the foundation soils, as well as their pronounced heterogeneity, which is illustrated in Figure 2. The significant dispersion observed in the Vs values measured through the SDMT reflects the variability in the grain size distribution and the degree of cementation characteristic of these materials, as shown in Figure 3.  
The section shown in Figure 2 reveals the greater presence of gravel in the alluvial terrace adjacent to the Aterno River. It also indicates that the lateral boundaries have been extended to three times the width of the A-A\({}^{\prime}\) section and modelled as absorbent edges. Figure 2(a) presents all the superimposed V\({}_{\text{S}}\) profiles from the backfilled boreholes shown in Figure 1, while Figure 2(b) displays only the V\({}_{\text{S}}\) profiles appropriately averaged according to the stratigraphy corresponding to the studied A-A\({}^{\prime}\) section. It is important to emphasise the characteristics of the profiles within the hospital area (H): (1) S\({}_{\text{3H}}\) shows a slight inversion of V\({}_{\text{S}}\) (over \(-\)20 m); (2) S\({}_{\text{2H}}\) shows a V\({}_{\text{S}}\) increasing with depth; (3) S  
shows a shallow inversion of V\({}_{\rm S}\). Instead, the profiles included within the university area (U) have the following characteristics: (1) S\({}_{\rm SU}\) shows a V\({}_{\rm S}\) increasing with depth; (2) S\({}_{\rm IU}\) shows a significant surface inversion for a thick layer. In this part of the basin, most of the significant HVSR peaks--clearly attributable to the fundamental resonance frequencies (f\({}_{0}\)) of the Quaternary deposits--fall within the 0.8-1.5 Hz frequency range. Higher frequencies (5-10 Hz) are generally associated with superficial fill materials and/or sandy lime soils [7; 8]. The depth of the bedrock (BR) was inferred from a well drilled in the area and was thus estimated at approximately 90 m. A V\({}_{\rm S}\) value of 1250 m/s was assigned to the bedrock. The mechanical and dynamical soil parameters for the geotechnical units (GUs) used for the 2D analyses are shown in Table 1. The subsurface model adopted for the 2D analyses was based on the reconstruction carried out in the preliminary 1D study shown in [9]. Moreover, the mechanical properties are based on the study by [PERSON] et al., 2011 [7] of the Aterno Valley, where the proposed 2D model may be considered a benchmark for future site effect studies. This model provides the opportunity to examine site effects in areas with complex underlying geology. The study by [PERSON] et al. (2011) [7] concluded that  
Figure 1: Location and map of the study area with test locations (S) and A–A\({}^{\prime}\) sections. Figure 2: Geological–geotechnical study section A–A\({}^{\prime}\) with soil material classification from boreholes and V\({}_{\rm S}\) profiles from SDMT shown in Figure 3. The sites with V\({}_{\rm S}\) inversion profiles are indicated in the circles.