Caribbean Earthquake of M6.5 Strikes off Barbados, 18 February 2014

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Location and tectonic setting of the 18 February Barbados earthquake. Image credit: USGS

Location and tectonic setting of the 18 February Barbados earthquake. Image credit: USGS

A magnitude 6.5 (M6.5, initially measured at M6.7) earthquake, which occurred 170km north of the Caribbean island of Barbados on 18 February 2014, caused the NOAA to release a warning of a potential local (though not regional) tsunami.

At the time of writing, however, no news media had reported that any such event had occurred; nor were there any indications of damage or injuries resulting form the tremor.

The United States Geological Survey’s damage forecast for this event (just a 1% probability of fatalities) reflects the fact that many of the building in the immediate area are resistant to earthquakes.

The Tectonic Setting of the 18 February Barbados Earthquake

The Caribbean is highly seismically active. The relatively small Caribbean plate lies between three others – the North American, South American and Cocos plates – resulting in a complex pattern of relative motions and differing fault mechanisms. The 18 February earthquake occurred at the eastern margin of the Caribbean plate, at a point where it converges with the North American plate at a rate around 2cm per year. The downwards movement of the denser North American plate creates a subduction zone.

Although the USGS has not yet published any detailed data on the earthquake, the available information on depth (17km) and location (the epicentre lay inside the overriding plate) suggests that it’s likely to have occurred as a result of faulting within the Caribbean plate rather than at the interface between the two. Fault maps of the area support this interpretation, showing roughly east-west trending normal faults in the over-riding plate in the area where the tremor occurred.

Major Seismic Events in the Caribbean

The Caribbean is subject to frequent low-level seismicity. Image credit: USGS

The Caribbean is subject to frequent low-level seismicity. Image credit: USGS

Given the tectonics of the area, residents of the Caribbean are accustomed to earthquakes; a map of seismic activity in the past 30 days shows over 250 tremors along the stretch of plate boundary between the Turks and Caicos Islands to the north and Trinidad and Tobago to the south.

Most of these, however, are small-magnitude (less than M4.0) and associated with ongoing movement along the Puerto Rico Trench – although this area did see a tremor of M6.4 on 13 January.

The immediate vicinity of the 18 February tremor doesn’t, as a rule, experience large earthquakes; the largest of recent years was the M6.3 near Guadeloupe in 2005 but others tend to be smaller than M6.0. Within this context, today’s tremor is a significant local event.

The Haiti earthquake of 2010 caused widespread devastation. Image: US Coastguard

The Haiti earthquake of 2010 caused widespread devastation. Image: US Coastguard

Elsewhere in the Caribbean, however, tremors can and do exceed M7.0 – especially further north and west along the plate boundary. The area around Puerto Rico has experienced five tremors of M7.0 or more in the past century and a half; and the most notable seismic event in the region, is the Haiti earthquake of 2010.

Although at M7.0 it is by no means the largest to strike, the poor housing and dense population in the country contributed to the deaths of an estimated 316,000 people.

Caribbean Earthquakes

Earthquakes are frequent hazards in the Caribbean. The 2010 Haiti earthquake was just five times larger than that of 18 February 2014; but the two demonstrate that it isn’t just the magnitude of a tremor which dictates the human cost, but the proximity and vulnerability of local populations.

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