Palaeoseismic event in the Broze Age in northern Sardinia (Italy) evidences from megalithic monuments

Megalithic monuments of northern Sardinia, referable to the Copper and Bronze age, are used to test the hypothesis that the observed building damage is of seismogenic nature. For this purpose have been analysed 100 megalithic sites covering an area of about 500 km2 occurring in an area geologically characterized by very low seismic activity and located in the horst shulders made up of Palaeozoic basement at the edge of Oligo-Miocene Logudoro basin. Observed monuments show structural damage including torsion of top block in rock-cut tombs (the so called "Domus de janas"), horizontal displacement of ashlars and collapse orientation in nuraghs. Observed collapses of nuraghs show a maximum of frequency around N, indicating a possible palaeosismicity activity. The proposed interpretation is in agreement with the occurence of recentmost volcanic activity of Plio-Pleistocene anorogenic cycle ending at about 0.5 Ka as well as the distribution of seismic events in historical times