For centuries, earthquakes have shaken Haiti, now reeling from a 7.2-magnitude tremor that struck early Saturday. Why are quakes so prevalent on the island nation?
The island of Hispaniola, home to both Haiti and the Dominican Republic, straddles four tectonic plates in the Caribbean ocean, Incorporated Research Institutions for Seismology said.
Earthquakes occur along the boundaries of these tectonic plates, which make up the Earth’s crust. These borders are called faults.
Haiti lies at the intersection of the Caribbean Plate and the Gonave, Hispaniola and North Hispaniola microplates, the institutions said.
And it’s “caught in the crunch” between the Caribbean and North America plates, where sudden releases of energy in the crust as the two plates grind together cause earthquakes.
The makeup of the crust near the Bahamas exacerbates the problem — thick limestone reef deposits more than three miles deep double the crustal thickness with buoyant materials that make it harder for the North American Plate to subduct, the organization said.
Subduction occurs when one plate slides beneath another plate into the Earth’s molten mantle, releasing some of the pressure without causing earthquakes.
Here are the latest updates from Haiti:
Haiti has two prominent fault zones. A continuation of the Septentrional fault runs through the north of Hispaniola, while the Enriquillo-Plantain Garden fault zone, runs through the south of the major Antille. The Saturday morning earthquake happened over the Enriquillo-Plantain Garden fault zone, where the magnitude 7.0 earthquake struck in 2010.
“It is an event that is possibly related to the event of more than ten years ago,” said Victor Huerfano, director of the Puerto Rico Seismic Network. “It’s the same fault.”
The Puerto Rico Seismic Network continues to study the event and monitor the region for aftershocks.
“The event was so strong, that still hours later, there are seismic signals arriving,” he said.
The latest 7.2-magnitude quake hit at 8:29 a.m. local time, concentrated in the southern and western parts of the country. There are reports of extensive damage and several aftershocks.
In 2010, a 7.0-magnitude earthquake in the capital of Port-au-Prince killed more than 300,000 people. Other major quakes were recorded in 1887, 1842, 1770 and 1751.
Magnitude measures the energy released at the source of the earthquake, the U.S. Geological Survey says. It replaces the old Richter scale.
Quakes between 7.0 and 7.9 magnitude can cause major damage, according to Michigan Tech. There are about 20 such quakes each year worldwide.