Wednesday, April 23, 2014
Tsunamis, spawned by earthquakes, have laid waste to communities in northern Japan and coastal areas on the Indian Ocean, but could one happen here?
FOR MORE information about the tsunami threat, go to: http://1.usa.gov/fDNK9T
Not likely -- but not impossible. So emergency management officials are developing plans just in case.
Last week, Cumberland County commissioners decided to accept a $39,000 grant to help pay for educational materials associated with a tsunami threat.
The federal money will pay for electronic message boards that could be deployed in an emergency, and for informational brochures that will be translated into the seven most common foreign languages used in the county.
"In the hierarchy of threats to Cumberland County, it's not very high, but it exists," said James Budway, the county's emergency management director. "I don't think it would be catastrophic in any shape or form."
But, he said, "In the end, whatever you predict, it may exceed what's predicted."
So, just in case, local, county and state officials have analyzed the potential impact of a surge of water from a tsunami spawned by a major earthquake in the Puerto Rico trench.
The impact would likely be restricted to the immediate coast, and people who live there would be urged to evacuate, he said.
"Our response is basically that anybody who is susceptible to a surge, whether storm or tsunami, is aware of it first and then to make intelligent decisions on what they may want to do with the information," Budway said.
A tsunami is caused by a massive volume of ocean water being displaced suddenly, usually by a major earthquake, said Stephen Dickson, marine geologist with the Maine Geological Survey.
When one of the Earth's tectonic plates suddenly slides beneath another, it can trigger a sudden rise in ocean level. That wave -- often called a tidal wave even though it has nothing to do with tides -- moves remarkably fast and carries tremendous force, even though it may be barely perceptible on the ocean's surface.
Videos taken in northeastern Japan last year show the ocean spilling over the shoreline, carrying away trucks, homes and anything else in its path.
While a tsunami could hit in the Atlantic, the destruction is likely to be nowhere near as dramatic, in large part because of Georges Bank.
The ridge at the outer edge of the Gulf of Maine would serve as a bulwark against a tsunami, Dickson said.
A tsunami would probably dissipate as it hit Georges Bank, with some of it spilling through northeast and southwest channels.
Maine is actually well along in its preparations for a possible tsunami.
The Maine Emergency Management Agency hosted presentations last year by the West Coast and Alaska Tsunami Warning Center, a clearinghouse for tsunami information and preparation that is continually analyzing seismic and other data to assess the tsunami risk.
"The difference between Maine and a place like Japan would be, our warning time would be much greater and our impacts would be much less, because the height of the wave would be less," said Dwane Hubert, MEMA's director of mitigation, preparedness and recovery.
The exercises helped ensure that if a tsunami were imminent, warnings would get to the right people, Hubert said.
Earthquakes can cause tsunamis, but Atlantic earthquakes are different from Pacific quakes. Instead of the Earth's plates crashing into each other, in the mid-Atlantic they are pulling away, being replaced by volcanic material.
However, the North Atlantic plate is colliding with the Caribbean plate. Scientists say a magnitude 9.0 earthquake in the Puerto Rico Trench would be the equivalent of 1 megaton of TNT and could create a tsunami traveling north at 500 mph, Dickson said.
"It would reach Bermuda in two hours and Maine in five or six hours," he said. "We would maybe hear from Bermuda that it really exists," and from specialized buoys in the Atlantic.
Warning systems would likely give Maine emergency responders time to move people off beaches and other low-lying areas along the coast, said Budway.
The rise might be at most 3 feet, depending on the tide, and it would go up and down for hours. Water pushing into bays and river mouths would stack up higher, increasing the damage upstream.
"The currents are what we have to be prepared for," Dickson said. "It will include water flowing up our rivers and estuaries, up the Penobscot River for example, and into Casco Bay," Dickson said.
Other areas of the East Coast would suffer much worse.
"Everything from Cape Cod south will experience higher waves and potentially much greater damage than we will in the Gulf of Maine," he said.
Other possible tsunami scen- arios include a massive landslide in the Canary Islands, sending a huge wave across the Atlantic.
Another possibility is undersea landslides in an area like Georges Bank, much closer to Maine.
The possibilities aren't just theoretical. A 20-foot-high tsunami spawned by an earthquake on Grand Banks hit Nova Scotia and possibly spilled into the Gulf of Maine in 1929, wiping out fishing villages and killing 28 people.
After the Indian Ocean tsunami in 2004, U.S. officials decided to upgrade the nation's tsunami warning system, leading to the Maine's exercises and improvements.
Staff Writer David Hench can be contacted at 791-6327 or at: