IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS002 Poster presentation 1811
Tsunamigenic potential of recently mapped submarine mass movements
offshore eastern Sicily (Italy): numerical simulations and implications for
the 1693 tsunami
Dr. Alberto Armigliato
Dipartimento di Fisica, Settore Geofisica Universita di Bologna IASPEI
Stefano Tinti, Andrea Argnani, Filippo Zaniboni, Gianluca Pagnoni
Eastern Sicily has long been recognised to be among the most exposed regions in Italy and in the entire
Mediterranean to tsunami hazard and risk. The historical tsunamis recorded along the Ionian coasts of
Sicily were generally associated to moderate-to-large magnitude earthquakes: the most famous is the
11th January 1693 tsunami, whose parent earthquake is believed to be the largest magnitude event of
the Italian history (M=7.4). Indeed, the possibility of tsunami generation by coastal and submarine
mass movements cannot be ruled out: the destabilisation of mass bodies induced by the volcanic
activity of Mount Etna, by the relevant seismic activity of the region or by a combination of these two
factors, together with the steep bathymetric gradients found in correspondence with the Hyblaean-Malta
escarpment just few kilometres offshore eastern Sicily, represents a highly hazardous combination of
factors as regards tsunami generation. Recent offshore surveys, including the multichannel seismic
survey MESC2001, carried out from 27 July to 16 August 2001, on board the R/V Urania of the Italian
National Council of Researches (CNR), mapped a number of possible landslide bodies along the
Hyblaean-Malta escarpment.Understanding the tsunamigenic potential of these mass instabilities is not
only important from the point of view of the tsunami hazard assessment along the coasts of eastern
Sicily, but it can also be useful in evaluating their possible role in the generation of historical events,
such as the January 11, 1693 tsunami. A lively debate exists on the source of the 1693 event, and one
of the key questions is whether the M=7.4 earthquake was the only source of the tsunami, or other
causes (such as submarine landslides, possibly triggered by the earthquake) contributed to the tsunami
generation. So far, numerical investigations of the event have been based only on the first hypothesis,
and they pointed out that the characteristics of the tsunami deducible from the available historical
accounts (size and spatial extension of effects) can be reproduced only by assuming an offshore
tectonic source.The main goal of this study is to make a first attempt to investigate the second of the
aforementioned hypotheses. Taking into account the largest of the mass movements mapped by
MESC2001, we model numerically the dynamics of the landslide and the generation and propagation of
the ensuing tsunami. In particular, the sliding motion is simulated with Lagrangian block models, UBO-
BLOCK1 and UBO-BLOCK2, developed at the University of Bologna, while the tsunami generation and
propagation is carried out through the finite-element code UBO-TSUFE, implemented by the same
research team. The main computed tsunami features are discussed, such as the time evolution of the
tsunami field, the spatial distribution of the minimum and maximum tsunami heights along the eastern
Sicily coastline, as well as the amplitude, period and first polarity of the tsunami waves in selected
coastal stations. We compare the numerical results with the historical evidences and try to draw some
preliminary conclusions on the possible role of the mapped landslides in generating the 1693 tsunami.
Keywords: eastern sicily, 1693 tsunami, landslide