‘A bomb directly under a city.’ Why shallow quakes like Haiti’s are more destructive

The major earthquake that rocked Haiti on Saturday originated only about six miles below the Earth’s surface, a so-called “shallow” event that seismologists say tend to be more destructive.

Shaking drops off with distance, so less seismic energy from extremely shallow earthquakes is lost on its way up, according to The Associated Press.

Shallow quakes can feel like “a bomb directly under a city,” Susan Hough, a U.S. Geological Survey seismologist, told AP. Deeper quakes can be more widely felt but tend to do less damage.

The 7.2-magnitude quake about 75 miles west of the capital of Port-au-Prince caused severe damage and killed more than 700 people, with hundreds more injured or missing, authorities say.

A 2010 quake that rocked Port-au-Prince, killing more than 300,000, also was very shallow, striking about 8 miles below ground, Britannica reported.

Earthquakes can take place up to about 435 miles below the surface, the USGS said. They occur when tectonic plates rubbing together on faults slip, releasing a sudden burst of energy.

Shallow earthquakes originate 40 miles or less below the surface.

Haiti, which lies at the border between the Caribbean and North American tectonic plates, has been rocked by major earthquakes throughout history.

The southwest region is particularly vulnerable to quakes because most buildings are built of mud or adobe blocks, the USGS said.

This story was originally published August 14, 2021 at 4:45 PM with the headline "‘A bomb directly under a city.’ Why shallow quakes like Haiti’s are more destructive."