Geophysical and geological signatures of an unknown fault in the historic center of Messina (Sicily, south Italy)

Analysis of seismic noise measurements shows a clear change of the Site Resonant Frequency across a NW-SE segment cutting the historic center of the town of Messina. This change indicates strong lateral heterogeneity of the sediment cover going from southwest to northeast across the segment and suggests the existence of a fault never reported by previous investigators, oriented differently from the NNE-SSW main structural system which is widely believed to have produced the magnitude 7.1 earthquake of 1908. Additional evidence of such a NW-SE fault has been obtained by surface geology and analysis of morphological and Digital Terrain Model data. Geologic observations clearly indicate normal faulting but are not able to identify eventual strike-slip components. Activity of this fault is documented at least until Middle Pleistocene based on stratigraphic evidence and borehole data, with likely prosecution during Upper Pleistocene. The new detected fault requires deeper investigation in the near future for evaluation of its real extent and present dynamics including eventual seismogenic attitude.