| Stromboli is one of
the most active volcanoes in the Aeolian island arc in south Tyrrhenian
sea, Italy. In the last 100 years the most relevant volcanic eruptions
have beenaccompanied by local tsunamis, that have caused damage and
casualties. In some cases the direct mechanism of local tsunami generation
is clear, i.e. pyroclastic flows entering the sea. In some others it is
uncertain and some speculation concerning the collapse of the eruptive
column on the sea surface or the failure of some underwater mass can be
made. But the ordinary activity is unlikely to generate large regional
tsunamis. These can be produced by the lateral collapse of the volcanic
cone that geomorphological and volcanological investigations have
proven to have occurred repeatedly in the recent history of the volcano,
with return period in the order of some thousands of years. The last
episode is dated to less than 5 ka BP, and left the Sciara del Fuoco scar
on the north-west flank of Stromboli.
Based on previous studies, the possible collapse of the
nortwestern sector of Stromboli and the consequent generation and
propagation of a tsunami are explored. The impact on Stromboli and on the
other islands of the Aeolian archipelago is estimated, as well as the
impact on the coast of Sicily and the Tyrrhenian coasts of Calabria. The
simulation is carried out by means of a double model: a Lagrangian block
model to compute the motion of the collapsing mass, and a finite-element
hydrodynamic model to compute the evolution of the tsunami. Two distinct
tsunami simulations are carried out, one on a very fine grid around the
source region to evaluate the tsunami near Stromboli, and one utilising a
coarser grid covering the whole south-east Tyrrhenian sea to compute the
tsunami propagation toward Sicily and Calabria. It is found that a
huge-volume collapse of the north-western flank of the Stromboli cone is
capable of producing a regional tsunami which is catastrophic at the
source and devastating on long stretches of Tyrrhenian coasts, but
particularly in the neighbouring islands of Panarea and Salina, and along
the Calabria coasts around Capo Vaticano. |