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 1822
Constraints on the source of the 20th February 1743 tsunamigenic
earthquake in Apulia, Italy, from numerical tsunami modelling and
geological evidences
Dr. Alberto Armigliato
Dipartimento di Fisica, Settore Geofisica Universita di Bologna IASPEI
Stefano Tinti, Giuseppe Mastronuzzi, Paolo Sans, Gianluca Pagnoni
According to the most recent version of the Italian Tsunami Catalogue, the 20th February 1743 tsunami
was generated by a strong earthquake (M=6.9) which severely hit the Salento peninsula (Apulia) and
the Greek Ionian Islands, and that was felt in a very large area, including Calabria, the Messina Straits
and Naples. The maximum damage due to the earthquake was suffered by the towns of Nard and
Francavilla Fontana in southern Apulia, where most buildings were ruined. The cities of Taranto and
Brindisi were also heavily damaged. The earthquake was responsible for more than 160 victims.
Historical accounts on the tsunami are scarce: the only available report describes some tsunami effects
in the harbour of Brindisi, where the sea withdrew. On the other hand, the impact of the tsunami waves
along the Ionian and Adriatic coasts of Apulia appears to be well documented from the geological point
of view. A recent detailed study on large boulder accumulations along the southern Apulia coasts and on
their depositional characteristics allowed not only to put them in relation to the 1743 event with a
reasonable degree of confidence, but also to formulate some hypotheses on the possible source area
(SSE of Apulia), on the direction of impact of the tsunami waves and on the highest tsunami runup (11
m). Based on these results and on some basic information coming from local tectonics, we take into
account a small number of seismic sources and for each of them we simulate numerically the ensuing
tsunami. More specifically, for each studied fault we compute the coseismic deformation of the sea
bottom and take it to be identical to the tsunami initial condition. The subsequent tsunami wave
propagation is computed by means of a finite-element numerical code, UBO-TSUFE, developed at the
Department of Physics of the University of Bologna, which implements and solves the Navier-Stokes
equations in the shallow-water approximation. For each run, we compare the numerical results with the
available geological and historical evidences: attention is posed especially on the tsunami wave
propagation direction, on the polarity of the first wave arrivals in some selected coastal stations in
southern Apulia and on the spatial distribution of the extreme water elevations along the coastlines. The
results are discussed in order to draw some preliminary conclusions on the most probable source area
and geometry for the 1743 tsunamigenic earthquake.
Keywords: apulia, numerical modelling, tsunami deposits