## 6 Conclusions  
We presented two case studies from two very different sites in order to validate the method in such different circumstances. The first consisted of three high-resolution seismic lines acquired along the roads of a village built on hard rock in Croatia. The second consisted of two high-resolution seismic lines acquired in a cultivated area in northern Italy. In both cases, we acquired P-waves as well as S-waves, the latter in two different polarizations: parallel (SV) and orthogonal (SH) to the seismic line. Furthermore, surface-waves were acquired in the two sites. However, in Croatia,no dispersive event could be identified and therefore no results could be obtained. This highlights the importance of acquiring SH-waves. We then performed first break tomography on all lines, for all wavefields.  
The results output by the presented survey method are of high value for engineering purposes, as well as for the overall geological and geotechnical characterization of the investigated areas. Specifically, from an engineering point a view, the sites were classified based on their V\({}_{\rm S30}\) as required by the current legislation. The method allows to investigate also other important properties of the subsoil, such as the V\({}_{\rm P}\)/V\({}_{\rm S}\) and the anisotropy of the medium. From the former, it is possible to infer the fracturing of the medium and its water saturation (i.e., the position of the water table). From the latter in the Croatian site, it was possible to compute the dip and strike angles of the bedding of the flysch, providing therefore a geologically valuable information, while in the Italian site, it confirmed the silty/clay composition of the sediments and their horizontal layering.  
The method proposed is non-invasive, replicable and relatively cheap, as the acquisition required only 2-3 days for each seismic line. Furthermore, it provides an in-depth characterization of the composition of the subsurface up to a depth of several tens of meters without the need for expensive procedures such as drilling and coring. Finally, these parameters are given along entire profiles, a few hundred meters long, making it attractive for the extensive characterization of geologically heterogenous areas.  
Given the value of the results and all the above considerations, we conclude that the method proposed is an optimal tool to perform an in-depth characterization of the shallow layers of the subsurface.  
Conceptualization, F.A., F.D.C. and G.B.; methodology, F.A. and G.B.; software, F.D.C. and G.B.; validation, F.D.C., G.B. and F.A.; formal analysis, G.B. and F.D.C.; investigation, F.A., F.D.C. and G.B.; resources, F.A. and F.M.; data curation, F.M.; writing--original draft preparation, F.D.C.; writing--review and editing, F.D.C.; visualization, F.D.C., G.B. and F.M.; supervision, F.A.; project administration, F.A.; funding acquisition, F.A. All authors have read and agreed to the published version of the manuscript.  
The research presented in this paper has been carried out within the PMO-GATE (Preventing, Managing and Overcoming Natural-Hazards Risks to mitGATE economic and social impact) project. Such project falls in the Interreg Italy-Croatia programme of the European Commission under project id 10046122.  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
We thank the crew involved in the two data acquisitions, in the names of [PERSON], [PERSON], [PERSON] and [PERSON]. Special thanks also to [PERSON] of the University of Split, who gave us important feedback on the results we obtained. A final thank to the Municipalities both of Ferrara and Kastela, who gave important help with the logistics.  
The authors declare no conflict of interest.