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Tsunamis A Risk In Populous Caribbean

This seismically active area has long felt the huge waves, but now the dense population raises even more concern.

By MATTHEW HAY BROWN, Courant Staff Writer

July 19, 2004
Copyright © 2004 THE HARTFORD COURANT. All rights reserved.

MAYAGÜEZ, Puerto Rico -- First the ground rumbled, shaking the coconuts from the palm trees and rattling the zinc roofs of the huts.

Then, as workers on land watched, the sea pulled away from the shore, exposing coral reefs and fish flopping on the wet sand.

And finally the waters came roaring back, less a wave than a great and sudden tide, smashing boats and shacks and buildings and trucks in a single blow.

"The sea rose up like 6 or 8 feet," José Ruiz Fusá, the son of a fisherman in Rincón, told a researcher decades later. "There it was that the people caught fear and began to run."

The great tsunami that pounded the northwest coast of Puerto Rico at mid-morning on Oct. 11, 1918, killed dozens of people. But that was when the northwest coast was a relatively sleepy corner of this Caribbean U.S. territory.

"We know it would be much more devastating with the amount of coastal development today," said Christa von Hillebrandt, director of the Puerto Rico Seismic Network.

At least 27 of the killer waves, which are caused by an underground earthquake or eruption, have battered the seismically volatile Caribbean in the past 500 years.

To prepare for the next tsunami, von Hillebrandt and her colleagues at University of Puerto Rico are developing an early warning system to detect them and advising the public of their dangers.

"These are highly unlikely events," von Hillebrandt said. "But the impact can be tremendous - and the disaster can be avoided."

Since last year, the Puerto Rico Tsunami Warning and Mitigation Program has been monitoring the region for earthquakes measuring magnitude 6.5 or more on the Richter Scale, and is developing an emergency advisory system similar to the flood warnings broadcast on radio and television.

But because tsunamis can strike before a warning can be spread, program leaders also are undertaking an extensive public-education campaign to prepare islanders to react immediately.

Investigators are combining computer models, topographical maps and census information to identify populations at risk - "a wake-up call," University of Puerto Rico Prof. Aurelio Mercado said. They're also giving presentations at shopping malls, training local emergency-management workers, running evacuation drills in public schools and distributing warning signs to coastal communities.

"We don't want a repeat of 1918," von Hillebrandt said. "We want people to be aware of the hazard areas, and if an earthquake occurs, where to go."

But that could be just the beginning. With more funding, she said, the program could staff a 24-hour warning center to advise not only Puerto Rico but its island neighbors, Central and South America and the eastern United States of seismic events - a Caribbean counterpart to the Pacific Tsunami Warning Center in Hawaii.

Florida Institute of Technology Prof. George Maul, a professor at Florida Institute of Technology and a member of the Intergovernmental Oceanographic Commission of UNESCO, has been calling for such a center for more than a decade.

"We may get fewer tsunamis in the Atlantic than in the Pacific," he said, "but the population density in Western Europe, the Caribbean and the eastern United States raises the specter of a much greater loss of life."

Found in all oceans of the world, tsunamis may form locally and strike quickly, as in the 1918 wave that was caused by an earthquake in the underwater Mona Canyon 10 miles northwest of Puerto Rico. Or they may travel vast distances, as in the 1755 tsunami that formed off Lisbon, Portugal, and slammed into the Caribbean islands of Antigua, Saba and St. Martin hours later.

The massive swells may speed across the open ocean at more than 500 mph. At landfall, they can strike with a force twice as destructive as a Category 5 hurricane.

Puerto Rico lies on a microplate near the fault line between the North Atlantic and Caribbean plates, which grind past each other at a couple of centimeters a year. The region experiences underwater earthquakes and landslides and is home to at least one active submarine volcano.

Ninety-one tsunamis have been reported in the region since 1498; scientists have verified 27 as true tsunamis and nine more as very likely true. The impact of a strike on a populated area can be catastrophic: by some estimates, as many as 1,800 people were killed by the tsunami that struck the northeast coast of the Dominican Republic, just across the Mona Passage from Puerto Rico, on Aug. 4, 1946.

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