Seismology and Geophysics: Understanding the Devastating Haiti Earthquakes

On August 14, 2021, a magnitude 7.2 earthquake struck Haiti. The largest earthquake in the region since 2010, the disaster left at least 2,000 people dead, 12,000 people injured, and nearly 53,000 houses destroyed. Two assistant professors in the MIT Department of Earth, Atmospheric and Planetary Sciences discuss why the region is susceptible to earthquakes and what has changed — in Haiti and in earthquake science — since the devastating 2010 event, when the country had only one seismometer.

Assistant professors Camilla Cattania and William Frank discuss the science behind the 2010 and 2021 earthquakes in Haiti. Camilla Cattania is a seismologist with experience in numerical modeling, earthquake physics, and statistical seismology; and William Frank is a geophysicist focused the physical mechanisms that control deformation within the Earth’s crust.

Q: Why is Haiti prone to earthquakes?

Cattania: I’ll start with the broad tectonics setting. The island of Hispaniola, which comprises Haiti and the Dominican Republic, is sandwiched between the North American plate to the north and the Caribbean plate to the south. Haiti is primarily on a tiny plate that’s sandwiched between the two. At each plate boundary it has faults, fractures within the Earth’s crust, running approximately east to west. The earthquake happened in the southern-most fault system, called the Enriquillo-Plantain Garden fault system, where there are faults with slightly different orientations, creating complex fault geometry. The northern plate is moving to the west while the southern plate is moving to the east, causing earthquakes along this fault zone.

Frank: Not only do you have the sliding motion from east to west, but you also have compressive, or squeezing, motion at the plate boundary that is accommodated by other nearby faults. For example, one of the big questions for the 2010 earthquake is: What fault did it actually occur on? It looked like it was right next Enriquillo-Plantain Garden fault system, but was it was on a translational, or sliding, fault or a compressive fault? There are lots of outstanding questions about the complexity of what, from far away, looks simple. Read more...

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