The Caribbean region (consisting of Central America, the northern part of South America, and the Caribbean islands) is one of the most active seismic zones in the world. Over the past 500 years, very significant earthquakes have caused deaths, property damage and financial losses. Although dozens of thousands of earthquakes have occurred in the Caribbean, some 400 are considered significant. The first great earthquake documented in the region occurred in 1498 in Venezuela. From that time to today, 434,543 deaths from earthquakes have been reported, but more than 300,000 died in the January 12, 2010, earthquake in Haiti alone, and financial losses were greater than that Caribbean nation’s annual budget.
Earthquakes are concentrated along the borders of the Caribbean Sea and the Pacific sides of the region’s countries. Over the past 500 years, earthquakes up to magnitudes of 8.3 have occurred. Based on the effects of some of these earthquakes, it is estimated that their intensity on the Modified Mercalli Scale (I-XII) reached as high as X (in which significant changes in the surface are seen, in addition to the collapse of structures). The depths of these historical earthquakes range from superficial (10-20 km) to deep (some 150 km).
What is the origin of the seismic activity in the Caribbean? The seismic activity is caused by the interaction of the Caribbean plate with at least four other plates: North America (in the Atlantic), South America (Atlantic and Pacific), and Cocos and Nazca (Pacific). In the Caribbean, the movement of the plates is about 20 mm/year, while in the Pacific it reaches 80 mm/year.
In the northern edge of the Caribbean plate, there are lateral movement faults (such as the Motagua fault in Guatemala, and the Septentrional and Plantain Garden/Enriquillo faults in Hispaniola); and extensional faults (Cayman trough). Further east, the North America plate moves at an oblique angle under the Caribbean plate (Puerto Rico trench). Here, earthquakes occur at greater depth. The Haiti earthquake occurred in the deformation area associated with the Plantain Garden fault.
In the Lesser Antilles, the North and South America plates move directly under the Caribbean plate, which generates not only a lot of seismic activity, but also important volcanic activity. To the south, the movement again is lateral, with large faults (El Pilar and Boconó faults) and superficial seismic activity. In western Venezuela and central Colombia there are more convergences (both the Caribbean and the Nazca plates, although the interaction of the Nazca and South America plates is 65 mm/year, which generates a lot of seismic activity and earthquakes of large magnitude).
Most of the seismic activity along the length of South America is associated with the subduction of the Cocos plate along the western coast of Central America, under the Caribbean plate. The speed of this subduction is up to 81 mm/year. This creates earthquakes as deep as 300 km, as well as a lot of volcanic activity. Also, on the Caribbean side is the deformation zone along the coast of Panama.
There are 20 seismic networks operated by seismic institutes in the Caribbean that monitor and report on earthquakes. Thanks to these institutions, we can know about the smallest and largest earthquakes and about the various faults in the region and the seismic dangers associated with them.
Autor: Christa von Hillbendt
Published: March 20, 2012.