Tsunamis are an Ongoing Threat to Humans
By University of Washington
May 6, 2005, 16:16
The tsunami that devastated south Asia coastlines and killed more than 200,000 people last December is a powerful reminder of just how dangerous those waves can be to humans.
Such reminders have been delivered periodically, sometimes several decades apart, during the last half-century. But the lessons have been largely ignored or forgotten by most people who didn't suffer direct consequences, said Jody Bourgeois, a University of Washington Earth and space sciences professor who studies historic and pre-historic tsunamis.
Bourgeois this week will urge fellow scientists to find ways to use the current heightened awareness of tsunamis as a means for broad public education about tsunami dangers and prudent safeguards. Such education should be conducted matter-of-factly, without playing on the fears engendered by December's events, she said.
"An important message for us to get out is that these things happen," she said. "Sumatra wasn't the first. Most people don't even know about Kamchatka in 1952, and it's been more than 40 years since the great Alaskan earthquake."
On Nov. 4, 1952, an earthquake with a magnitude perhaps as high as 9 struck off the Kamchatka Peninsula, a part of Russia separated from Alaska by the Bering Sea. The great quake spawned a tsunami that killed thousands on Kamchatka and in the Kuril Islands and caused damage thousands of miles away in Hawaii, Peru and Chile. Because it occurred in the early days of the Cold War, the scope of the disaster in the Soviet Union wasn't widely reported.
A huge earthquake off the coast of Alaska in 1964 and a magnitude 9.5 quake off the coast of Chile four years earlier triggered Pacific-wide tsunamis. The waves caused deaths and tremendous damage in the immediate area of the earthquakes, but they also caused damage thousands of miles away.
The danger is mounting year by year, Bourgeois said, because greatly swelling numbers of people are living and playing along coastlines vulnerable to sometimes immense tsunamis. That's the message she will deliver to scientists Friday afternoon in San Jose, Calif., at the annual meeting of the Cordilleran Section of the Geological Society of America, during a session on problems faced by the growing population of the Pacific Rim.
Bourgeois and others have found ample sedimentary evidence of Pacific basin tsunamis, either confined to relatively small locations or spread over vast distances, going back thousands of years. In some cases, other evidence supports the scientific data. For instance, records in Japan reflect damage caused by a tsunami in 1700 that was generated by a magnitude 9 earthquake off the coast of Washington and Oregon.
But no tsunami has had a death toll comparable to the one triggered last Dec. 26 by a great earthquake off the coast of the Indonesian island of Sumatra. Earlier this month, the revised death toll from that event stood at about 217,000. Indonesia, Thailand and Sri Lanka were by far the hardest-hit nations.
Because the region has become a major tourism center, those who died came from many nations. Bourgeois noted that some of the 20 or so U.S. and Canadian fatalities came from the heartland, areas far from the coast that seldom experience earthquakes and never see tsunamis.
"We need to get that message to people in Kansas, not just along the coast," she said. "Even if you live in Kansas, or Siberia, you should know about tsunamis. In our mobile society, we travel to lots of different places, for vacations and for work."
A key lesson for someone caught in such a disaster, she said, is that you probably will survive the earthquake and you also can survive the tsunami. If you are on a coastline and feel a large earthquake, for instance, you should be prepared to move inland or to higher ground. If there is no escape route and the terrain is flat, look for sturdy buildings at least two stories tall to possibly ride out a surge of water that could be 40 feet high.
Tsunamis also can be triggered by events such as undersea landslides, collapsing volcanoes and asteroid impacts. The chances are stacked against either of the latter two, but if they should occur the effects would be spectacular.
"I don't think I conceived of how big an event a tsunami could be until I saw those videos from Indonesia and Thailand," Bourgeois said, "and I've studied them for more than 20 years."
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