Tsunami evacuation signs go up on our beach. Really?
From the Sebastian Inlet to Round Island Park, all along the ocean on our barrier island, 28 signs have gone up over the past few weeks warning that “in case of earthquake or tsunami evacuate the beaches.” Really? Earthquakes or tsunamis in Indian River County? Is that possible?
Oceanographers, physical scientists and meteorologists agree that a tsunami is possible here, but the probability is very low.
As for an earthquake, that would occur thousands of miles away, giving beachcombers three to nine hours to skedaddle from a one to three foot water wall surging toward A1A, that would probably not be life-threatening.
But scientists disagree on whether an earthquake in the Atlantic Ocean where one is most likely to affect the U.S. east coast – near Puerto Rico or off the coast of Portugal – would likely be the cause of a tsunami here, or a landslide on the continental shelf.
“First of all, to assign probability to a tsunami along the east coast of Florida is pure black magic,” said international tsunami expert Aurelio Mercado, a physical oceanography professor at the University of Puerto Rico.
“It may be tomorrow or it may be five, six, seven generations from now. But our models show that a tsunami along the coast of Florida is more likely to come from a localized landslide along the continental shelf (off the coast of Florida) than from an earthquake in the Puerto Rican Trench or off the coast of Portugal,” he said.
In fact, said Mercado, recent studies of a 10-foot wave that unexpectedly surged onto land at Daytona Beach in 1991, injuring 70 people, points to it being caused by a localized landslide along the continental shelf off the Florida coast, rather than a squall line or unknown factors previously offered to explain it.
“With a localized landslide, like the Daytona wave, you’d have no warning,” said Mercado. “It could come in the middle of the night, a silent killer without a signal – either tomorrow or in a thousand years.”
Which means: The signs may not matter.
On March 11, 2011, people worldwide were haunted by video footage of the Japanese tsunami that destroyed the city of Miyako and much of the Sendai area of Japan, killing 15, 867 people.
Indian River County emergency management director Etta LoPresti said that her office received dozens of calls from Vero Beach residents asking if a tsunami could occur here.
“That’s when we started looking into it and went into action,” said LoPresti.
She met with National Weather Service meteorologist Scott Spratt and oceanography professor George Maul to talk about the concern. The three agreed that Indian River County would join the growing number of coastal areas in the U.S. that are becoming “tsunami ready.”
In California, there are dozens of these “TsunamiReady” areas; in South Carolina and North Carolina, one area each; and in Florida, three areas – Indian Harbor Beach in Brevard, Mayport near Jacksonville and, now, Indian River County.
“The west coast of the U.S. is a much more likely area for a tsunami than the East Coast,” said Mercado. “Still, awareness is never a bad thing.”
Scott Spratt, meteorologist with the National Weather Service in Melbourne who worked on the TsunamiReady program, said that the closest scientists could come to offering the “return period” for east coast tsunamis is “every 100 years.”
“But it doesn’t mean you couldn’t have one and then another right after,” he said.
The thinking with Maul, LoPresti and Spratt was to “increase awareness about tsunami possibility, as well as educate people and put a communication system in place.”
The signs are part of that TsunamiReady plan.
“We hope they’ll get people’s attention and make them want to learn more,” he said.
An earthquake generated tsunami would probably not be life threatening if it came ashore in Indian River County, predicted Spratt.
Still, records show that a tsunami in 1755, which was generated by an oceanic earthquake off the coast of Portugal, had waves between eight to 12 feet that went well beyond the beach areas in Georgia and north Florida, near Mayport.
Spratt recalled another huge wave pushing beyond the beaches, like the Daytona wave of 1992, that occurred between Naples and Tampa in 1995.
But, he said, to his knowledge, no system had confirmed the cause, though Mercado said these rogue waves are most likely caused by a localized landslide in the ocean.
“While any tsunami is not probable off the coast of Florida, we had to ask ourselves what would happen if one occurred and no plan was in place,” said Spratt. “That’s why you now see the signs along the beach.”
An earthquake generated tsunami off the coast of Puerto Rico would take three to five hours to get to Indian River County. One off the coast of Portugal would take eight to nine hours to get here, he estimated.
“You wouldn’t get word 48 hours ahead of time as you do with hurricanes,” he said. “You’d have three to nine hours to act.”
LoPresti said warnings would go out on TV and radio, as well as in person on the coast.
Working with Spratt and LoPresti was George Maul, oceanography professor at the Florida Institute of Technology in Melbourne.
Maul listed tsunamis over the past 300 years that have occurred along the east coast between the Caribbean islands and Canada – 1755 in Lisbon, 1867 in the British Virgin Islands, 1886 in Charleston, S.C., 1929 in Newfoundland.
But the one he has focused on occurred in 1868, coming ashore in St. Thomas, VI and killing 100 people.
“Think of the U.S. cruise ships there now,” he said. “Another tsunami could kill 12,000 to 15,000 people. “
Which is one more reason, he said, that people need to be more aware of the possibility.
“Our intention is to create an educated citizenry,” he said.
In the far-flung town of Palmer. Alaska, northeast of Anchorage, James Waddell a physical scientist at the National Oceanic and Atmospheric Administration, tracks possible tsunami-causing forces off the east coast of the U.S.
He is quick to say that he thinks the signs along the beaches of Indian River County are “a good thing.” He lists tsunami possibility locations, including those given by Mercado, Spratt and Maul: the Puerto Rican Trench, off the coast of Lisbon, Portugal and the continental shelf off the coast of the US east coast.
Right now, he is looking at suspicious seismic activity off the British Virgin Islands.
“Off the U.S. east coast, though,” he said, “you have shoals and bands to break waves and disperse energy, which would tend to slow down and break up a tsunami,” he said.
LoPresti, director of the county’s emergency operations, said until a few years ago, she had never given tsunamis “any thought.” But now they’re on a list of dangers to the area.