St. Augustine, Trinidad and Tobago, W.I. --December 28th, 2004 – A tsunami is an ocean wave or series of waves caused by an abrupt disturbance of the ocean floor that displaces a large mass of water. Tsunamis are caused either by tectonic earthquakes (earthquakes generated by the movement of plates) occurring both in and out of the region, or volcanic events such as dome collapses/landslides or the eruption of submarine volcanoes. While it is possible for the region to be hit by a tsunami such as the one recently experienced in Asia, scientists currently believe that there is a very low probability of this phenomenon occurring. In the past 500 years there have been four earthquake-generated tsunamis to affect the Caribbean, none of which was more than 1m in amplitude. In total about 350 people were killed by these events. These tsunamis occurred as a result of earthquakes in: • May, 1842, Haiti – An intense local tsunami was believed to have killed up to 200 people in the town of Port-de-Paix • November, 1867, Virgin Islands – Death toll about 20, all in the Virgin Islands • October, 1918, Puerto Rico – Death toll about 29 in Puerto Rico • August, 1946, Dominican Republic – An intense local tsunami which mainly affected the town of Matanzas where up to 100 people were killed In July 2003, a major dome collapse from the Soufriere Hills Volcano in Montserrat caused a tsunami that was experienced in Guadeloupe at about 1m high and in some parts of Montserrat at 4m in amplitude. While recent events in Asia have caused much concern over the Caribbean’s vulnerability to tsunamis, it is important to note that all oceans can experience tsunamis but there are more large, destructive tsunamis in the Pacific Ocean because of the many major earthquakes along the margins of the Pacific Ocean and also because dip-slip earthquakes (which involve vertical rather than lateral ground motion) are more common in the Pacific than elsewhere. As a result of the immediacy of the tsunami hazard to countries in the Pacific, there is currently a tsunami early warning system in that region. There is no tsunami warning system in the Caribbean. The first sign of an approaching tsunami is usually a significant retreat of the sea. As a result, the trailing waves pile on top of the waves in front of them, thereby significantly increasing the height of the wave before hitting the shore. Although a tsunami advances much slower as it approaches land, its momentum is powerful enough to cause severe destruction. If you are close to the sea and the water retreats by an abnormal amount, move to high ground at once. While it is possible that the region could be affected by earthquake-generated tsunamis, scientists currently believe that the more immediate threats posed by earthquake hazards such as collapsing buildings, falling electricity lines, ruptured gas lines, rock slides and/or landslides on mountains and hillsides (as recently witnessed in Dominica, Trinidad, the British Virgin Islands and the Cayman Islands) are more of a present danger to the region. Greater focus should, therefore, be placed on ensuring that effective public education programmes are undertaken to sensitize the public to these hazards and serious consideration should be given to constructing sound earthquake-resistant buildings. For updates on these and other geologic events occurring in the region please visit the Seismic Research Unit’s website at www.uwiseismic.com. Based at the University of the West Indies in St. Augustine Trinidad, the Seismic Research Unit is the agency responsible for monitoring earthquakes and volcanoes throughout the English-speaking Eastern Caribbean. Source: Seismic Research Unit