‘Real and serious’ threat of tsunami in Caribbean

Last December, scientists warned that an earthquake in the Caribbean would almost certainly trigger a tsunami that could devastate the region. The same researchers are now emphasising the need for an early warning system to prepare the Caribbean, Gulf of Mexico and the Atlantic Ocean to face the threat.

Writing in the 24 December 2004 edition of the Journal of Geophysical Research, Uri ten Brink of the US Geological Survey and Jian Lin of the Woods Hole Oceanographic Institution reported that at least 13 major earthquakes had hit the region in the past 500 years. Of these, several had generated tsunamis of considerable destructive power.

In 1946, a tsunami triggered by an earthquake measuring 8.1 on the Richter scale killed 1,600 people.

With earthquakes occurring in the region every 50 years or so, the researchers say that it is only a question of time before another tsunami strikes. As there are 20 million people living in the area, the authors call for both early warning systems and for the public to be educated about the risk.

The threat is due to the region’s geology. The Puerto Rico and Hispaniola trenches — deep depressions formed when one plate of the Earth’s crust is pushed beneath another — are both capable of producing earthquakes of significant force, measuring 7.5 or higher on the Richter scale.

A further threat is the so-called Septentrional fault zone, which passes through the heavily populated Cibao valley in the Dominican Republic on the island of Hispaniola. Here, the Earth’s crust has fractured along faults susceptible to further movement.

By analysing data relating to past earthquakes and using three-dimensional models, ten Brink and Lin calculated how stress changes in and near the oceanic trenches after each earthquake.

The study indicates that earthquakes in deep offshore trenches have the potential to trigger further earthquakes or add to the stress on fault lines on nearby islands.

“We don’t want people to overreact, [we] just [want to] make them aware of the potential risk of such rare and yet deadly events so they are prepared,” says Lin. “It is similar to knowing about hurricanes or tornadoes and being prepared to react when one is coming.”

“The risk is undoubtedly real,” says Ted Nield, science and communications officer at the Geological Society of London, United Kingdom. “Early warning is credible technically, and practical if local evacuation plans and public education throughout the affected area goes with it.”

Nield told SciDev.Net that arguments against early warning systems citing the infrequency of tsunamis and the cost of preparing for them – as were heard relating to the Indian Ocean prior to last month’s tsunami – “come to seem very threadbare indeed when the rare event happens, hundreds of thousands die and billions of dollars have to be found”.

The Caribbean Disaster Emergency Response Agency, based in Barbados, is discussing setting up a tsunami early warning system for the Caribbean with partners including the Seismic Research Unit at the University of the West Indies, the Pacific Tsunami Warning Centre and the University of Puerto Rico Seismic Network.

According to a report in The Barbados Advocate last week (14 January), Richard Robertson, acting head of the University of the West Indies Seismic Research Unit, said that before the region invests in a tsunami warning system, it should strengthen existing networks and focus on public education about the threats seismic activity can pose.

Link to related news story in The Barbados Advocate

Link to abstract of paper by ten Brink and Lin in Journal of Geophysical Research

Reference: Journal of Geophysical Research 109, B12310, doi:10.1029/2004JB003031 (2004)