The 2010 Earthquake
Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
Earthquakes in the Caribbean
Present day plates of the Caribbean. Accretionary complexes like the Greater Antilles are made of rock slices piled up by plate convergence. Thus, they tend to be loaded with faults. Some of these pieces move semi-independently of the main plate and are termed microplates. One, shown in yellow, is the Gonave Microplate and was the source of the catastrophic 2010 earthquake.
The two peninsulas that extend west from Haiti enclose a gulf called the Gulf of Gonave, which is named for the large island within the gulf. The name Gonave probably comes from the native Taino name "Guanabo."
Outlining plates in plate tectonics is often literally a matter of connecting the dots. This map shows earthquakes of Magnitude 4 and greater in the Central America region from 1990 to 1996 (red: 0-33 km depth, orange: 33-70 km, green: 70-300 km, blue: 300-700 km) [SE after Dale Sawyer, Rice University, http://plateboundary.rice.edu]
Spreading ridges are heavy lines, subduction zones are toothed lines with the teeth on the upper plate, and transform faults are light lines. Transform faults are plate boundaries where the plates slide horizontally past each other without diverging or converging.
Note that in Central America and the Lesser Antilles, earthquakes start out shallow at the plate boundary and get deeper away drom it. This is the princuipal way we know there's a dipping slab of crust descending into the mantle there. Under Central America it dips northeast and under the Lesser Antilles, it dips west. When the slab gets down about 100 km or so, the slab and adkacent manrle begin to melt and magma rises to create a chain ofvolcanoes like Arenal in Costa Rica and the infamous Mont Pelee on Martinique.
A closeup of the Gonave Microplate. The plate boundary isn't a simple clean break across Jamaica, and it has lots of earthquakes as a result, generally small.
Major earthquakes on the Enriquillo Fault, Hispaniola. There have been other major earthquakes on other faults. For example, a large earthquake struck Cap Haitien on the north coast (CH) in 1842. One reason the quake caught everyone by surprise is there had not beem a large earthquake on the Enriquillo Fault in over a century.
Source: Bakun, William & Flores, C. & ten Brink, Uri. (2012). Significant Earthquakes on the Enriquillo Fault System, Hispaniola, 1500-2010: Implications for Seismic Hazard. The Bulletin of the Seismological Society of America. 102. 18-30. 10.1785/0120110077.
A map of the largest caribbean earthquakes. Prehistoric earthquakes can sometimes be inferred from effects on archaeological sites. One especially noteworthy event is the unlabeled event in Jamaica. That's the former site of Port Royal, a notorious pirate hangout known for loose wealth and morals. The kind of place you picture in Pirates of the Caribbean, only X-rated instead of PG. The earthquake in 1692 demolished the town and a tsunami finished the job, something seen as divine justice by many, especially the Spanish. Ironically, the British had largely stamped out piracy by the time of the earthquake.
The 2010 earthquake was Magnitude 7.0, not very large as earthquakes go. Damage would be worst in the orange and red areas. The reason the earthquake killed over 200,000 people is unsafe building construction. The death toll is only an estimate since bodies were collected and buried without an accurate count.
Engineers and seismologists have a saying: "Earthquakes don't kill people, buildings kill people." The spectrum of safety ranges from steel-frame skyscrapers and wood-frame houses at the top through reinforced masonry, unreinforced masonry and adobe, or mud brick at the bottom. Poor quality masonry and weak framing frequently mean that earthquakes that would be serious and damaging in developed nations are catastrophic killers in underdeveloped nations.
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Created 18 February 2021, Last Update