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 Oral Presentation 1774
Potential landslide tsunami waves offshore Ischia island, (Italy)
Dr. Violante Crescenzo
IAMC-CNR Institute for Coastal Marine Environments National Research Council IAHS
Chiara Biscarini, Silvia Di Francesco
Recent submarine explorations at Ischia island, a volcanic complex located north-west of the Gulf of
Naples, Italy, showed evidences of debris avalanches and catastrophic collapses including an
amphitheatre scar to the south, and hummocky deposits in the southern, western and northern
offshore. The island is characterised by a series eruptions that continuously modified its morphology,
and by an high rate of tectonic uplift of the central sector, the Mt Epomeo , that has raised up to 780 m
in the past 30 ky with an average rate of 20 mm/y. The studied mass movements in the form of muddebris
flows, debris slides, rock-falls and debris avalanche radiate from Mt Epomeo as a consequence of
its volcano-tectonic uplift and have an age spanning from prehistory to the present. Debris volumes
range from 0.1 km3 from smaller events to more than 2-3 km3 for the largest avalanche, whose run-out
is probably larger than 45 km as deduced from large blocks occurring in the southern continental slope
until 1100 m depth. In the northern offshore an engraved fan-shaped valley, likely related to the
emplacement of a very recent landslide event, is laterally constrained to the west by a relevant
depositional levee. For all these events, large masses of volcanic material have entered the sea both in
shallow waters and in deep waters likely producing tsunami waves spreading all over the Tyrrhenian sea
and possibly into the bay of Naples . To test we work out a 3D simulation of the potential tsunami event
associated to one of the major landslide events. The numerical model is based on geological data, so
that the fluid dynamic simulation allows to investigate, evaluate and represent the three-dimensional
water waves generation and propagation resulting from landslide phenomena. The problem is
schematised as a multiphase multicomponent fluid flow (compressible air, water and landslide material)
and the numerical tool is a finite volume transient fluid dynamics model based on coupling mass and
momentum conservation (Navier Stokes) equations to a Volume Of Fluid (VOF) model, which actually
keeps and updates the field of volume fraction of one fluid in each cell and is widely used to track the
interface of two immiscible fluids, such as water and air. A previously performed validation with both
laboratory and real event data, has demonstrated that the present model is able to predict with a high
level of accuracy the temporal evolution of water waves.
Keywords: landslide generated waves, numerical simulation, tyrrhenian sea