Photograph courtesy Hermann M. Fritz
Published February 23, 2010
Though surveying damage and rescuing survivors was of utmost priority for several weeks, scientists are now starting to examine some of the side effects of the temblor, such as the tsunamis.
The waves, which averaged about ten feet (three meters) high, slammed shores along the Bay of Port-au-Prince and the southern coast of the island of Hispaniola (see map), which is shared by Haiti and the Dominican Republic.
At least one wave hit the shore as far as 62 miles (100 kilometers) away from the earthquake's epicenter, near Port-au-Prince, Haiti.
Tsunamis are rare though not unheard of in the Caribbean—a 1946 wave in the Dominican Republic killed nearly 2,000 people, said Hermann Fritz, a civil and coastal engineer who worked with a team from Haiti's Quisqueya University to study the tsunamis.
Yet the Haiti tsunami swarm was unusual, since earthquakes usually need to be bigger than the recent magnitude 7.0 quake to spawn the killer waves, said Fritz, whose team will present its findings Wednesday at the American Geophysical Union's Ocean Sciences Meeting in Portland, Oregon.
"It's a warning for the Caribbean," said Fritz, of the Georgia Institute of Technology. In another scenario, for example, after a bigger earthquake, "the cards can be stacked differently, and there can be a bigger tsunami."
Haiti Tsunamis Were Deadly Spectacle
Fritz and colleagues visited Haiti after the recent earthquake to look for physical evidence of the tsunamis, which had been detected by the U.S. National Oceanic and Atmospheric Administration's Caribbean buoys.
Satellite images gave the team possible locations of wave impacts. At these sites, the researchers found sand deposits, debris, tree scars, and other signs that tsunamis had hit throughout the region.
The team also discovered that the tsunami swarm had included two types of waves.
Tectonic tsunamis are caused by the movement of plates on the seafloor. Landslide-generated tsunamis occur when unstable land collapses into the water following an earthquake.
Tectonic tsunamis usually take minutes to hours to arrive on shore, giving people trained in spotting the danger time to escape. Landslide tsunamis are more localized and are usually much smaller.
In Haiti, a man and two boys were killed by a landslide wave at Grand Goave, a town along the Bay of Port-au-Prince, as they watched from the shore, the team's survey found. Several coastal homes were also swept out into the water.
The victims were among many earthquake survivors who had gathered on Haitian beaches to watch the incoming waves as "kind of a spectacle" instead of fleeing, Fritz said.
For people familiar with tsunamis, feeling the earth shake is the obvious sign to run from the shore, he said.
"Once you see the reef and the fish on the seafloor [as the water draws back], that's the second warning to head inland." (Related: "Tsunami Warning Signs, Facts in Wake of Samoa Quake.")
Not surprisingly, the poorest country in the Western Hemisphere lacks basic tsunami preparedness, such as warning signs on beaches, Fritz added.
But as Haiti picks up the pieces following the record January 12 earthquake, educating the public about tsunami waves is crucial: With more than 200 years since the last "big one" in Haiti, bigger earthquakes—and giant tsunamis—may be possible.
"This time," Fritz said, at least in terms of tsunami damage, "we were lucky."
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