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Fissures off Va. Coast May Presage Tsunami, Experts Say
By Dan Eggen and Jacqueline L. Salmon
Washington Post Staff Writers
Wednesday, May 3, 2000 ; A01

Researchers setting out to sea from the Virginia coast this weekend hope to find answers to a new scientific riddle: Could tsunamis, the large, destructive waves that have terrorized Japan and the rest of the Pacific for centuries, pose a threat to the mid-Atlantic coast as well?

According to the latest research, they might. Scientists have discovered a 25-mile series of cracks along the edge of the continental shelf, about 100 miles east of Virginia Beach and the mouth of the Chesapeake Bay.

If the fissures are moving, they could be the beginning of the type of underwater landslides that trigger tsunamis, according to a report just published in the May issue of Geology magazine.

Scientists estimate that a landslide from the fissures could send a wave 20 feet high hurtling up the region's beaches. Such a wave hitting southern Virginia would be similar to the force of a severe hurricane. In 1972, Hurricane Agnes caused the worst flooding the Washington area had seen in decades; it washed out roads and bridges and killed 118 people from Florida to New York.

The Virginia Beach-Norfolk-Newport News area, with 1.5 million people, would be closest to the origin point of the wave, but flood waters also could push up the Chesapeake Bay and the Potomac River and inundate waterfront areas of Annapolis, Washington, Alexandria and other low-lying communities.

"The potential impact would depend on the tides and all sorts of other complications," said Neal W. Driscoll, a scientist at Woods Hole Oceanographic Institution in Massachusetts, one of three authors of the Geology article. "The risk associated with this is slight, but finite. These tsunamis do happen, and they can happen in all kinds of places."

A tsunami--which means "harbor wave" in Japanese--is notoriously hard to anticipate or predict. An underwater earthquake or landslide can trigger a fast-moving series of waves spread out across a path that is broad but barely detectable on the surface, until the waves reach shallow water.

A tsunami can cross the open ocean at 450 miles an hour, then rise to 100 feet as it approaches the shore, according to the Federal Emergency Management Agency. But even in the tumultuous, earthquake-prone Pacific Rim, it is rare that any one place will be hit by a wave.

Yet even on North America's Atlantic coast, tsunamis are not unprecedented. In 1929, a wave measured at up to 40 feet slammed into the southern coast of Newfoundland, killing 51 people. The landslide in that case was about the same size as the one that researchers fear could happen off the Virginia coast.

"If a massive landslide occurred this close to the coast, you would only have about 20 minutes' warning," said Jeffrey K. Weissel, of Columbia University's Lamont-Doherty Earth Observatory, who also is part of the research team. "With a hurricane, you often have hours or days. In that respect, the tsunami threat is even more acute."

In 1998, a tsunami struck Papua New Guinea with almost no notice, killing more than 2,200 people.

Emergency management officials in the Washington area say they were surprised by the scientists' report, conceding that they have never considered the possibility of a tsunami. Officials said they need more information before deciding whether to design tsunami disaster plans.

"This is not something that you traditionally hear of on the East Coast," said Janet Clements, of the Virginia Department of Emergency Services.

If a surge of water moved up the Potomac, low-lying areas such as Reagan National Airport, Old Town Alexandria, Mount Vernon and the George Washington Memorial Parkway could be under water, officials said.

"It would be bad," said Alexandra T. Craig, deputy coordinator for emergency services in Fairfax County. "You've just added something to my list of things that I need to worry about."

In Ocean City, Md., yesterday, emergency officials consulted with tsunami experts before briefing the mayor and City Council about the potential danger.

Driscoll, Weissel and colleague John A. Goff, of the University of Texas, plan to set out to sea Saturday for two weeks to get a closer look at the potential landslide area. The researchers will use special sonar equipment to determine how recently the cracks opened and, perhaps, predict how soon a tsunami could occur.

The Geology article stresses that "it is unclear whether these cracks are fossil features or are active and therefore likely to produce a potentially large submarine landslide in the near future." Driscoll and Weissel said that if their examination shows that the cracks are recent, they will install monitoring equipment to see whether they are moving.

Driscoll said the cracks were not the only thing that caught researchers' attention: The fissures are just north of an Ice Age landslide that occurred about 18,000 years ago--which is not all that long in geologic terms. "If it was just the cracks themselves, that might be different," Driscoll said. "But this has happened before in this area."

Eddie Bernard, a tsunami expert with the National Oceanic and Atmospheric Administration, said underwater landslides are comparable in power and speed to avalanches.

"The behaviors of flooding would also be similar to a hurricane. . . . It can be devastating," said Bernard, chairman of the National Tsunami Mitigation Program in Seattle.

Although earthquakes are the most common cause of tsunamis, landslides, or a combination of the two, can also trigger them. The researchers say that there may be a number of explanations for the crack formations off the Virginia coast, from the release of trapped methane gas to erosion caused by ocean currents.



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