Caribbean safe from tsunamis — expert

Dr Richard Robertson, head of the University of the West Indies Seismic Research Unit (SRU) yesterday said there was a “low probability” of the Caribbean region being hit by tsunamis of the magnitude which killed thousands in Asia on Boxing Day. In a release yesterday, the SRU said while it is possible for the region to be affected by earthquake generated tsunamis, scientists currently believe that there are more immediate threats posed by the earthquake hazards such as collapsing buildings, falling electricity lines and ruptured gas lines, rock slides and/or landslide on mountains and hillsides as recently experienced in Dominica, Trinidad, British Virgin Islands and Cayman Islands.

The 9.0 earthquake in Asia occurred off the west coast of Sumatra where several large geological plates are located. A 1,000 km section along the boundary of the plates shifted and triggered the displacement of water and the tsunamis which washed away villages in Indonesia, Sri Lanka and India. Robertson said the formation of a tsunami depended on the kind of fault (break in a layer of rock) and its displacement and the depth of the ocean. The earthquakes in the region caused “small shallow waves. “We need to make sure buildings could withstand the ground shaking. Damage to buildings is more likely to happen.” He said an earthquake of the magnitude of 9.0 “will cause a lot of damage.”

Robertson said many buildings were not constructed properly and the assumption is made that they are engineered to a certain standard and could withstand the ground shaking. “A lot of buildings are self help and don’t necessarily conform. A lot of buildings are brick and cement and will fall down in an earthquake.” Robertson said  regional seismological associations are sharing data and working toward setting up a warning system. The SRU said in the past 500 years there have been four earthquake-generated tsunamis to affect the Caribbean. None of them were more than 1 m in amplitude. A total of 350 people were killed. In May 1842, an intense local tsunami was believed to have killed 200 people in Port-de-Paix, Haiti, and in November 1867, 20 people were killed in the Virgin islands. October 1918, 29 people were killed in Puerto Rico, and in August 1946, in the Dominican Republic it caused the death of 100 people in the town of Matanzas.

In July 2003, a major dome collapsed from the Soufriere Hills in a volcano in Montserrat that  caused a tsunami 1m high that was experienced in Guadeloupe and in 4m amplitude in some parts of Montserrat. The SRU said while recent events in Asia have caused much concern over the Caribbean’s vulnerability, “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, an early warning system was established. “There is no tsunami warning system in the Caribbean.” Updates on geological events in the region can be obtained at the SRU’s websie: www.uwiseismic.com.