Combined geophysical methods to study a complex archaeological settlement: the case of Nuraghe S'Urachi (Sardinia)

The "Nuraghe" is an archaeological stone structure in Sardinia dating from about the second millennium B.C.. These structures sometimes occur as individual buildings or as an aggregation of these in the so-called Nuragic reggia or Nuragic complex. Surrounding the Nuragic complex usually was the settlement. S'Urachi is a fortified, partially excavated Nuragic complex consisting of ten towers, only seven currently visible partially above ground, joined by a surrounding wall. The central part of the complex and its internal conformation are, until today, buried and unknown. Outside the Nuragic complex, traces of small structures have been found extending within the first meter below ground level, while the Nuraghe complex rises about four meters above the present ground level. The use of electrical resistivity tomography (ERT) and seismic refraction tomography is here proposed to study the inner part of this main complex structure, while ground penetrating radar (GPR) and multifrequency electromagnetic method (FDEM) are presented and compared for the analysis of the shallower archaeological remains located outside, discussing for each method its power and limits relative to the scale and the specific archaeological question.