Why catastrophic earthquakes hit Haiti so often

At least 1,297 people have died after the powerful earthquake struck Haiti on Saturday, where at least 5,700 people were injured.

The Caribbean country has long been suffering from earthquakes like Saturday's, which had 7.2 magnitude. In the 18th century, two strong earthquakes flattened the city of Port-au-Prince twice in 19 years.

The 21st century has proven equally difficult. Saturday’s powerful quake killed 1,297 and injured thousands more. Eleven years earlier a major tremor killed nearly a hundred thousand people.

Haiti sits near the intersection of two tectonic plates that make up the earth’s crust. Earthquakes can occur when those plates move against each other and create friction. Haiti is also densely populated. Plus, many of its buildings are designed to withstand hurricanes — not earthquakes. Those buildings can survive strong winds but are vulnerable to collapse when the ground shakes.

What makes Haiti prone to earthquakes?

The Earth’s crust is made up of tectonic plates that move. And Haiti sits near the intersection of two of them — the North American plate and the Caribbean plate. 

Multiple fault lines between those plates cut through or near the island of Hispaniola, which Haiti shares with the Dominican Republic. What’s worse, not all of those fault lines behave the same way. 

“Hispaniola sits in a place where plates transition from smashing together to sliding past one another,” said Rich Briggs, a research geologist at the US Geological Survey’s Geologic Hazards Science Center. 

“It’s like a rock stuck in the track of a sliding glass door,” he said. “It just does not want to move smoothly because it’s got so many different forces on it.” 

What caused the most recent quake? 

Saturday’s magnitude 7.2 earthquake likely occurred along the Enriquillo-Plantain Garden fault zone, which cuts across Haiti’s southwestern Tiburon Peninsula, according to the USGS. 

It’s the same fault zone along which the devastating 2010 earthquake occurred. And it’s likely the source of three other big earthquakes in Haiti between 1751 and 1860, two of which destroyed Port-au-Prince. 

Earthquakes are the result of the tectonic plates slowly moving against each other and creating friction over time, said Gavin Hayes, senior science adviser for earthquake and geologic hazards at USGS.

“That friction builds up and builds up and eventually the strain that’s stored there overcomes the friction,” Hayes said. “And that’s when the fault moves suddenly. That’s what an earthquake is.”

Why earthquakes in Haiti are so devastating

There are several factors such as being a seismically active area, a high population density of 11 million people and buildings that are often designed to withstand hurricanes, not earthquakes, for Haiti’s being devastated from temblors.

Typical concrete and cinder block buildings can survive strong winds but are vulnerable to damage or collapse when the ground shakes. Poor building practices can also play a role. 

The 2010 quake hit closer to densely populated Port-au-Prince and caused widespread destruction. Haiti’s government put the death toll at more than 300,000, while some reports commissioned by the US government placed it between 46,000 and 85,000.