Geophysical methods to recognise preexisting structures under an important archaeological site

The most characteristic Sardinian constructions are the “nuraghe”, all around the world there are examples only there. The nuragic period began from the Bronz Age to the Steal Age. A famous one is “Su Nuraxi” of the Barumini nuragic site (near Cagliari), that is the bigger between the 7000 nuragic sites in Sardinia. Researchers of several disciplines are studying to know more about their function, their constructive modality and their scope. Near the village there is a temporal stratification that probably continue under the surface soil. In some nuraghe site there are signs of pre-existing culture, with examples of neolithic villages. It would be possible that some nuragic sites were been chosen because of these pre-existing structures. The acknowledgement of those constructions near a such important archaeological site is very hard and often impossible. For the nuragic constructions were made without foundations we have applied geophysics methods, among them the seismic and the electric type, with emitters and geophones on the rest plan. We have used seismic tomography with P and SH waves to recognise probably pre-existing structures. High velocity zones are in correspondence of probably older constructions, while low velocity zone could represent poor resistance zones. The geophysical methods applied on the nuragic site have permitted to characterize the points in which take part with a static restoration, in some of them we have really found visible craks, in others not. These results have shown smaller resistance zones to take part for a static restoration. In Conclusion, the totality of the geophysical methods can be used to perform the static restoration and the electrical tomographies give important information on the groundwater paths, this is very interesting because the surrounding zones are devoid of water.