## 3 Results
### Synthetics HVSR in Selected Sites  
Synthetic data are used to test models in comparison with observations. In geophysics, 1D or 2D/3D subsoil profiles may be available after field investigation, including uncertainties according to the implemented technique. Validation testing of these models or even more their refinement can be performed after they are compared with actual observations [67; 68]. Such an approach is presented in this section. Figure 16: Fundamental frequency (f\({}_{\rm o}\)) in relation to the depth-to-bedrock based on the 76 HVSRs and the underlying bedrock of the Durres basin. In red circles flat HVSRs are depicted. Figure 17: Spatial distribution of the four HVSR site categories in the city of Durres, together with iso-depth contours. Bedrock depth iso-contours by [30]. The noise sources were assumed to be randomly distributed around each station in a 1 km radius and lying at depths ranging from 0 to 10 m. The locations for which synthetic recordings of ambient noise were generated are shown in Figure 18. The minimum distance between synthetic sources was 3 m, and the maximum was 1 km. The soil profiles of each site were deduced from the output of the Durres seismic microzonation study [30] and are given into Table 3. In the absence of any information about quality factors Q\({}_{\text{p}}\) and Q\({}_{\text{s}}\), we assumed Q\({}_{\text{p}}\) = 2Q\({}_{\text{s}}\) = V\({}_{\text{s}}\)/5 [69; 70]. Synthetic spectral ratio HVSRs were calculated using Geopsy, following the recommendations of the SESAME guidelines. In Figure 19 synthetic HVSRs (black dashed line) are plotted together with the corresponding observed ones (black solid line) using the closest experimental ambient noise measurement site. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**2 West**} & \multicolumn{3}{c}{**1 West**} & \multicolumn{3}{c}{**P38**} & \multicolumn{3}{c}{**DURR**} \\ \hline H (m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) & H(m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) & H(m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) & H(m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) \\ \hline
20 & 190 & 1500 & 10 & 80 & 400 & 10 & 150 & 1450 & 10 & 120 & 1400 \\ \hline
10 & 210 & 1550 & 5 & 120 & 1400 & 20 & 235 & 1550 & 16.7 & 201 & 1500 \\ \hline
20 & 233 & 1580 & 10 & 201 & 1500 & 30 & 250 & 1570 & 23.3 & 233 & 1580 \\ \hline
0 & 700 & 2000 & 55 & 233 & 1580 & 80 & 265 & 1600 & 40 & 242 & 1600 \\ \hline  & \multicolumn{3}{c}{**0**} & \multicolumn{3}{c}{700} & 2000 & 0 & 700 & 2000 & 0 & 700 & 2000 \\ \hline  & \multicolumn{3}{c}{**BHA**} & \multicolumn{3}{c}{**SH17**} & \multicolumn{3}{c}{**BH15**} & \multicolumn{3}{c}{**P40**} \\ \hline H (m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) & H(m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) & H(m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) & H(m) & V\({}_{\text{s}}\) (m/s) & V\({}_{\text{p}}\) (m/s) \\ \hlineFigure 19: Synthetic (dashed line) versus observed (solid line) HVSRs for the eight selected sites on the West-East cross section of Figure 18.  
Comparisons between synthetic HVSRs (Hisada 1D) and observed HVSRs for the examined eight sites in Figure 19 show that the fundamental frequency is generally similar for all sites, though the amplitude of synthetics is consistently higher, up to double around the fundamental frequency as in the case of P40. In two cases (1 West and BHA) a double peak appears in the synthetics, which contrasts the actual data. The shape of the synthetic HVSR is different from the observed one in the cases of 1 West, P38, DUR, BHA, and SH17. The underlying structure at these stations is laterally heterogeneous, indicating possible 2D/3D effects. For the sites 2 West, BH15 and P40 a lower amplitude of the actual HVSRs is observed, most probably due to attenuation of surface layers (low Q-values of the uppermost layered structure).