Why Earthquakes In Haiti Are So Catastrophic

It happened again.

Over the weekend, Haiti was hit by a magnitude 7.2 earthquake that crumbled homes and buildings and killed more than 1,200 people.

Rescuers are still working to find survivors amid the rubble. The death count is expected to rise.

More than a decade ago, a similar quake left an estimated 220,000 dead, more than 1 million people displaced and roughly 300,000 injured.

These two events are part of Haiti's history of major destructive earthquakes, records of which go back centuries.

Researchers say the country's unique geology make it seismically active — and prone to devastating earthquakes. A combination of factors, however, leaves the country especially susceptible to damage from these events.

Why is Haiti so susceptible to earthquakes?

Haiti sits on a fault line between huge tectonic plates, big pieces of the Earth's crust that slide past each other over time. These two plates are the North American plate and the Caribbean plate.

There are two major faults along Hispaniola, the island shared by Haiti and the Dominican Republic.

The southern one is known as the Enriquillo-Plantain Garden fault system.

It's this fault that the U.S. Geological Survey says caused Saturday's quake and the same one that caused the January 2010 earthquake.

The USGS believes the Enriquillo-Plantain Garden fault zone can be blamed on other major earthquakes from 1751 to 1860. The agency said none of these quakes has been officially confirmed in the field as associated with this fault, however.

A history of catastrophic earthquakes in Haiti

One of the earliest major recorded earthquakes in Haiti occurred in the 1700s, according to the USGS. Others followed, with researchers cataloging events that left hundreds dead and destroyed homes and businesses.

• Nov. 21, 1751: A major earthquake destroys Port-au-Prince and causes major destruction in nearby towns. Witness accounts of the event from the National Centers for Environmental Information recount the devastation. "Houses and factories were thrown down at St.-Marc, Lkogbne, and Plaine du Cul-de-sac. Crevices formed and abundant springs of nauseous water broke forth," researchers who witnessed the event described it. "Great landslips occurred and the beds of the rivers changed direction."
  
• June 3, 1770: An earthquake hits Port-au-Prince again. Researchers described the event as "one of the strongest shocks recorded on the Island of Haiti." An estimated 200 people in the nation's capital died as a result of the earthquake.
  
• April 8, 1860: This earthquake occurred farther west of the 2010 earthquake, near Anse-à-Veau, and was accompanied by a tsunami. "At Anse-a-Veau, crevasses sliced across the streets and 124 houses were demolished; at Miragoane, the bridge sank; at Petit Goave, all the houses were abandoned ... ," researchers said of the event. "Ships in the harbor of Les Cayes felt the shock, as did ships at sea."

Before the 2010 earthquake, there hadn't been another major quake along the Enriquillo-Plantain Garden fault zone for about 200 years.

Building to withstand hurricanes, not earthquakes

The USGS says it recorded 22 magnitude 7 or larger earthquakes in 2010, the same year as the devastating earthquake in Haiti. However, despite an active year, almost all the fatalities were produced by the major temblor that hit on Jan. 12 of that year, the USGS said.

It struck around the densely populated capital of Port-au-Prince, contributing to the high death toll.

But the way structures are built in Haiti is also believed to have contributed to the loss of life and property.

Due to the 1751 and 1770 earthquakes and minor quakes that occurred between them, local authorities started requiring building with wood and forbade building with masonry, according to the USGS.

In the years since, Haitians have focused on building their homes to withstand the bigger threat in the neighborhood — hurricanes.

Structures made of concrete and cinder block hold up well during storms but are more vulnerable during earthquakes, according to The Associated Press.

More earthquakes may be ahead

In 2012, researchers wrote that the 2010 earthquake "may mark the beginning of a new cycle of large earthquakes on the Enriquillo fault system after 240 years of seismic quiescence."

"The entire Enriquillo fault system appears to be seismically active; Haiti and the Dominican Republic should prepare for future devastating earthquakes," researchers said.

It's still too early to determine the long-term impact of Saturday's earthquake. What is certain is the unique pressures facing Haitians in the days ahead.

The country still has not fully recovered from the 2010 earthquake and Hurricane Matthew in 2016.

Haiti was already suffering from political instability following last month's assassination of President Jovenel Moïse. Moïse's death has since left a power vacuum that's been filled by interim Prime Minister Ariel Henry, a 71-year-old neurosurgeon and public official.

The nation is also bracing for another threat as Tropical Depression Grace threatens to bring heavy rains on Monday.

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