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.
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 an earthquake or an erupting volcano. Its capacity to travel over a wider area in a shorter time than a hurricane, 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 Indian Ocean tsunami and again in March 2011 in Japan.
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 (less than 50km depth), in the region, greater than magnitude 6.5.
Potentially, there are two groups of earthquakes which may generate tsunamis in the Caribbean. These are:
- Earthquakes occurring within the region 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.
- 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 1755 Lisbon Earthquake and Tsunami near Portugal and the La Palma Volcano in the Canary Islands. Click on the video below to view PTWC’s animation of this historical tsunami.
Tsunamis caused by large volcanic eruptions at or below sea level also pose a threat to the Eastern Caribbean. The submarine (underwater) volcano Kick-‘em-Jenny 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.