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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 Poster presentation 1801
Vulnerability of the Argentina coasts to tsunami effects
Dr. Roberto Antonio Violante
Argentina Hydrographic Survey IGCP 464 Argentina Delegate IAPSO
Walter Dragani
The Southwestern Atlantic coastal regions have been traditionally considered of low hazard probabilities
of being affected by tsunamis. The main reason is the geotectonic emplacement in a stable, tectonically
inactive, passive continental margin. However, some geological, topographical and oceanographic
aspects of the region should be reviewed as they could favor the occurrence of destructive events or
increase damage. The Scotia arc, locatedin the southernmost extreme of South America, is a highly
dynamic convergent margin with frequent occurrence of earthquakes and volcanic eruptions. The most
recent example was a 7.3 magnitude (Richter scale) earthquake occurred in 2003 with epicenter near
Orcadas Islands (60.55S- 43.49W), which induced an ocean wave that was rapidly cushioned by the
neighboring oceanic ice-field. The Argentina coasts were affected by the consequences of the 2004
Sumatratsunami. It produced small sea-level fluctuations measured at tide gauge stations in different
coastal emplacements between 37 - 39S, where short waves in the tidal curves with maximum heights
of 27 cm and wave periods between 20-120 minutes were recorded (Dragani et al., 2004). Also the
neighboring Brazilian coasts recorded the phenomena (Frana and de Mesquita, 2006). Considering the
configuration and relative geographical position of the Argentina coasts, the vulnerability to long ocean
waves originated by submarine events like earthquakes, volcanic eruptions and slides in the Scotia Arc
and surroundings cannot be rejected. The smooth and gently sloping continental shelf is a feature that
can behave as a ramp for ocean waves approaching to the coast driven by either climatic or geological
processes. The variable shelf width (decreasing from 600 to 170 km from South to North) and the
morphology of the adjacent continental slope should be considered as probable factors affecting ocean
waves movement. Regarding coastal morphology, there is an alternation of areas with different
susceptibility to damaging effects coming from processes and events originated in the ocean. They are:
a) low-lying regions located few meters above sea level (river mouths, deltas, estuaries, coastal plains,
etc.), considered as probable hazard areas with high potential of populations damage; and b) high
cliffed coasts elevated several tens of meters above sea level which should not offer any substantial risk
except for their possibilities of suffering strong erosion and structural unstability derived from it.The
interplay between coastal and submarine morphology, oceanographic and climatic aspects as well as
geological processes should be considered under an integrated perspective for evaluating the real
potential of the region to the impact of tsunamis.
Keywords: tsunami, argentina continental margin, scotia arc