In the past 500 years there have been ten confirmed earthquake-generated tsunamis in the Caribbean Basin with four causing fatalities. An estimated 350 people in the Caribbean were killed by these events. Click here for an overview of damaging tsunamis in the Caribbean.
Tsunami risk in the Caribbean
During the relatively short 500-year period of written Caribbean history, tsunamis have inflicted a small amount of losses compared to other hazards such as windstorms, earthquakes and volcanic activity. The impact of a large tsunami can be as devastating as earthquakes or an erupting volcano. Its capacity to travel over a wider area in a shorter time than hurricanes, gives a tsunami the potential to unleash destruction on regional and hemispherical scales, especially if a warning system is not in place. This was convincingly demonstrated by the December 2004 tsunami in the Indian Ocean.
The Eastern Caribbean islands lie in a setting where major structural changes are occurring in the Earth’s crust. All known sources capable of causing tsunamis (that is, earthquakes, volcanic eruptions, landslides) occur within striking distance of the Eastern Caribbean, and there are also distant sources across the Atlantic. Since the islands lie in an area of relatively high earthquake activity for the Caribbean, the most likely tsunamis to affect the Eastern Caribbean are those which can be triggered by shallow earthquakes (<50km depth), in the region, greater than magnitude 6.5.
Eastern Caribbean Islands. Volcanic islands are shown in red.
Potentially, there are two groups of earthquakes which may generate tsunamis in the Caribbean. These are:
(1) Earthquakes occurring within the region which may generate local tsunamis (by local we mean only nearby islands are affected). In the past 500 years there have been approximately 50 local earthquakes with the potential to cause a tsunami but only 10-20% of these earthquakes actually generated tsunamis that caused significant flooding.
(2) Distant earthquakes occurring outside of the region may generate tele-tsunamis. These pose a somewhat lower threat than tsunamis caused from local earthquakes. The primary tele-tsunami sources are the Azores-Gibraltar fracture zone that produced the well documented Lisbon Earthquake and Tsunami near Portugal in 1755 and the La Palma Volcano in the Canary Islands.
Tsunamis caused by large volcanic eruptions at or below sea level also pose a threat to the Eastern Caribbean. The submarine volcano Kick-‘em-Jenny (submarine volcano) located 9 km north of Grenada erupts on average every 11 years. At least two of those eruptions, in 1939 and 1965, generated small tsunamis that were witnessed on the north coast of Grenada. Detailed studies of the physical structure of Kick-‘em-Jenny conducted in 2002-2004, however, have shown that the volcano does not currently pose an immediate tsunami threat, but it is possible that future eruptions could change this situation.
The historical record suggests that potentially destructive tsunamis occur at an average rate of 1-2 per century in the Caribbean. The hazard is not the same throughout the islands. The north-eastern Caribbean region near Puerto Rico and Hispaniola is more susceptible to tsunamis. The average rate of occurrence in this area has approached 1 every 50 years in the last 200 years. In other sub-regions such as the southern Caribbean there are no historical records of destructive tsunami impacts.
The recurrence rate for tsunamis in the Caribbean is approximately: 1 destructive tsunami per century for local earthquakes and 1 destructive tsunami per 200 years for distant earthquakes. It should be noted that these recurrence rates are small, but not negligible.
Caribbean Tsunami Early Warning System
Currently, there is no tsunami early warning system being operated in the Caribbean. There is, however, a multi-national multi-agency initiative to establish a program for reducing the risk to various coastal hazards in the Caribbean and adjacent regions (Central and South American countries along the Caribbean Basin), but it may be several years before this is complete. The programme involves most existing regional institutions and agencies already involved in the monitoring and study of coastal and other natural hazards, along with several disaster management organizations. Initially, priority will be given to the development of a Tsunami Warning System (TWS) and support programmes to empower threatened communities to respond correctly to alerts and warnings. A key player in this effort is the Caribbean sub-commission of the Intergovernmental Oceanographic Commission (IOC).
The United States Government has supported the effort by making a commitment to extend the Global Seismic Network to include nine new stations in the Caribbean region, with three in the Eastern Caribbean. Another component of the US Government’s contribution will be the installation of five state-of-the-art sea-level sensing devices in deep waters on both sides of the island chain. Each station in both seismic and sea-level monitoring networks will be linked by satellite telemetry and will provide real-time data to US and Caribbean based warning centres. These new networks will play a pivotal role in the initial shaping of the regional tsunami warning system that will ultimately incorporate and leverage the resources of existing networks.
In September 2006, the Seismic Research Centre embarked on a project to significantly upgrade its seismic monitoring network as part of this regional effort to establish a Caribbean tsunami early warning system. This project was made possible through the generous support of the American people via a USAID Office of Foreign Disaster Assistance (USAID/OFDA) grant of US$249,680. The project also received financial support from the Government of Trinidad & Tobago. This upgrade will enable the SRU to more quickly and accurately locate earthquakes which could potentially trigger a tsunami.
In the mean time, if an earthquake occurs that can or has triggered a tsunami that may affect the Caribbean, the Pacific Tsunami Warning Center (PTWC) will send a warning to specific government agencies in the Caribbean – the Seismic Research Centre is one of those agencies. The procedure for communicating this warning to the general Public, however, is a component that is yet to be developed.