Discrimination of tsunami sources (Earthquake vs. Landslide) on the basis of historical data in Eastern Sicily and southern Calabria

摘要

The source mechanisms responsible for large historical tsunamis thathave struck eastern Sicily and southern Calabria are a topic of robust debate. We havecompiled a database of historical coeval descriptions of three large tsunamis: 11 January1693, 6 February 1783, and 28 December 1908. By using accounts of run-up andinundation and employing an approach proposed by Okal and Synolakis in 2004, wecan provide discriminants to define the nature of the near-field tsunami sources (faultdislocation or landslide).Historical reports for the 1908 event describe affected localities, maximum runups,and inundation areas. However, for the 1693 and 1783 tsunamis, reports arelimited to inundation and occasional run-up estimates. We calculate run-up valuesfor these events using available relations between inundation and run-up. Weemployed the model of Okal and Synolakis to the obtained profiles of tsunamirun-up along the inundated shorelines. The 1908 run-up data distribution confirmsthat the tsunami is compatible with a seismic dislocation source, whereas the1783 data supports contemporary observations and recent offshore investigations suggestingthat the tsunami was produced by an earthquake-triggered submarine landslide.Analysis of the 1693 event data suggests that the tsunami was generatedduring a tectonic event and thus a seismogenic source should be found offshore.