Morphological evidence of Holocene coseismic deformation in the Taormina region (NE Sicily)

In southern Italy, strongly uplifted coastal regions are located along the footwall of the main seismogenic fault segments which affect the Tyrrhenian side of southern Calabria and the Ionian coast of eastern Sicily. This morphotectonic picture is generally associated with high-level historical seismicity. An anomaly is represented by the Ionian coast of NE Sicily that, located on the footwall of the offshore Taormina Fault, is affected by very low to absent historical seismicity. A detailed levelling survey of dated Holocene marine notches has been carried out along the coast of Taormina and Capo S. Alessio, at the southern termination of the Taormina Fault, where a converging set of Late Quaternary strandlines marks the tip of this offshore structure. The Holocene marine marks, represented by three main notch levels separated by lithophaga bands dated at 5 ka and post-3.2 ka, are severely tilted towards the onshore and show a clear divergence from the southern tip of the Taormina Fault towards the north. Taking into account the slow rate of sea-level rise characterising the Central Mediterranean during the last 5 ka (0.3–1.0 mm/year), the vertical distribution of the Holocene strandlines can be interpreted as the result of shortperiod variations in the rate of tectonic uplifting. The notches and their related bio-morphological bands developed at low-rate of uplifting and have been displaced by three major seismic events in the past 5 ka, the strongest of which (M~7) occurred at about 3.2 ka. This confirms the temporary seismic gap for the Taormina Fault and strongly suggests that the seismogenic potential of this sector of Sicily needs to be re-evaluated.