Abstract
Abstract. We present geological evidence for paleotsunamis along the ~230 km-long coast of eastern Sicily (Italy); combining this information with historical data, we reconstruct a unique history of tsunami inundations. We integrate data on 38 paleotsunami deposits (from fine sand layers to boulders) collected at 11 sites (one offshore). The geological data record traces of large tsunamis which have occurred during the past 4 millennia. Chronological constrains include 14C, 210Pb and 137Cs, OSL and tephrochronology. When compatible, the age of the paleotsunami deposits is associated to historical events, but it is also used to highlight unknown tsunamis. Average tsunami recurrence interval (between 320 and 840 yr) and minimum inland tsunami ingressions (often greater than the historical ones) were estimated at several sites. On the basis of this work, the tsunami catalogue is implemented by two unknown tsunamis which occurred during the first millennium BC and by one unknown regional tsunami, which occurred in 650–770 AD. By including this latter event in the eastern Sicily catalogue, we estimate an average recurrence interval for strong tsunamis of ca. 385 yr. Comparison and merging of historical and geological data can definitely contribute to a better understanding of regional and local tsunami potential and provides robust parameters to be used in tsunami hazard estimates.
Highlights
The critical importance of reliable tsunami hazard assessment models and effective prevention plans were tragically highlighted by the occurrence of the 2004 Sumatra, 2010 Chile and 2011 Japan destructive earthquakes and tsunamis.Tsunami hazard assessment, early warning systems, as well as prevention and emergency plans have to be based on the knowledge of the potential tsunamigenic sources of the expected tsunami effects and of their frequency during time
Eastern Sicily was chosen for our investigations because it was affected in historical times by large earthquakes followed by devastating tsunamis (Fig. 2)
By integrating geological data on paleotsunami deposits discovered at 11 distinct sites along the ca. 230 km-long coast of eastern Sicily, we reconstructed the geological tsunami inundations history of the region, substantially extending back in time the historical record (Tables 1 and 2)
Summary
The critical importance of reliable tsunami hazard assessment models and effective prevention plans were tragically highlighted by the occurrence of the 2004 Sumatra, 2010 Chile and 2011 Japan destructive earthquakes and tsunamis. Given the relative rarity of tsunamis, even in areas such as the Mediterranean and Japan where the historical record for large events may go back in time for about two millennia, the historical occurrences of past tsunamis are likely not to be representative of all the possible tsunamis hitting the region To overcome these actual limitations, during the past decades, approaches based on earthquake geology and paleoseismology (see the pioneering work of Atwater and Moore, 1992) have been applied to the geological identification and dating of tsunamis of the past (hereinafter paleotsunamis). The eastern Sicily coastal area is densely populated with numerous large cities overlooking the Ionian Sea, historical and archaeological sites punctuating the coastline along with industrial centres and military bases All this highlights the urge for a detailed analysis of the actual tsunami hazard/risk and for the establishment of effective prevention measures. Historical and geological evidence for paleotsunamis is used to reconstruct a history of tsunami inundations in the region, to highlight potential inundation extents and to discriminate the nature of the causative sources, local, regional or basin-wide
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