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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 1746
Destructive tsunami-like waves (meteotsunamis) at the Balearic Islands:
observations and numerical modelling
Dr. Ivica Vilibic
Physical Oceanography Laboratory Institute of Oceanography and Fisheries IAPSO
Sebastian Monserrat, Alexander B. Rabinovich, Hrvoje Mihanovic
In light of enhanced activity in the study of tsunamis and their source mechanisms, we consider
tsunami-like destructive waves generated by atmospheric disturbances such as atmospheric waves,
pressure jumps, frontal systems, and squalls. Such hazardous sea level oscillations (meteotsunamis)
occur regularly in the region of the Balearic Islands (Western Mediterranean) where they are known as
rissaga. Destructive rissagas with heights 2 m take place every 4-5 years. A recent devastating rissaga
event occurred on 15 June 2006 in Ciutadella Harbour (Menorca Island) with reported wave heights
greater than 4 m. More than 40 boats were damaged and the event caused an economic loss of several
tens millions of euros. Unfortunately, there were no working tide gauges in the inlet or on the shelf
during the event. However, we have been able to use previous observational data to formulate an
efficient 2D numerical model of extreme long waves generated in this region. Specifically, we use data
for the period 1989-1999 with focus on the comprehensive hydrophysical experiment LAST-97
undertaken in 1997 which included a triangle of precise microbarographs and eight bottom pressure
gauges installed on the shelf and in bays/inlets of the Mallorca and Menorca islands. We re-examine
these data to estimate magnitude, speed and direction of travelling atmospheric disturbances and
associated generated long ocean waves. To understand the generation mechanism of meteotsunami
waves, we also consider those cases for which strong atmospheric disturbances did not produce a
noticeable sea level response. Parameters of the atmospheric disturbances are used as inputs to the
numerical model. Simulated ocean waves are in good agreement with observation. The verified model is
then used to simulate the 2006 event. Finally, the sea level measurements and numerical computations
are used to assess general tsunami issues for the Balearic region which is also prone to tsunamis of
seismic origin; a very recent and well-known example is the 2003 Algerian tsunami.
Keywords: meteotsunamis, field measurements, modelling