- SAN FRANCISCO -- Last week's catastrophic tsunami in Papua New Guinea could
be repeated anywhere along the West Coast of the United States, experts
say.
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- Indeed, it's only been 34 years since
a far more moderate tsunami struck the California coast, killing11 people
in Crescent City.
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- To prepare for such a disaster, state
and federal officials and scientists in California, Oregon, Washington,
Alaska and Hawaii are busy:
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- Establishing a deep-ocean array of seismographs
that can, via satellite, transmit warnings of tsunamis to the West Coast
-- perhaps up to hours in advance --giving people time to flee to higher
ground.
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- Trying to identify West Coast harbors,
coastal towns and bays most vulnerable to tsunamis.
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- Trying to increase awareness of the tsunami
risk to the West Coast.
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- The Papua New Guinea tragedy, which killed
at least 1,300 and as many as 6,000 people, "might be a wakeup call
for people living near the ocean in earthquake-prone areas," says
oceanographer and tsunami expert Eddie Bernard of Seattle. "I'm not
saying this as an alarmist, I'm saying it as a point of fact: This is a
hazard you need to be concerned about, just as you need to be concerned
about other hazards in your everyday life."
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- By 2001, scientists from the National
Oceanographic and Atmospheric Administration expect to finish installing
six tsunami-detecting buoys in deep Pacific waters, says Bernard, who chairs
the National Tsunami Hazard Mitigation Program run by NOAA.
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- Two buoys are being tested just off quake-prone
Alaska. They are attached to seismometers on the ocean floor that sense
major oceanic quakes.
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- A wire transmits the quake signal to
the buoy on the water's surface. From an antenna on the buoy, the signal
flies via satellite to the nation's tsunami-warning centers near Palmer,
Alaska, and Ewa Beach near Honolulu.
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- Much of the tsunami-awareness program
stems from 1992, when a 7.1-magnitude quake in the Cape Mendocino-Petrolia
area caused a relatively harmless tsunami, perhaps up to 3 feet high, on
the north coast. By the time the tsunami hit Point Reyes, it was only 5
inches high.
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- But to the shock of scientists, the wave
persisted up to eight hours as it bounced up and down the coast, "like
coffee sloshing in a coffee cup," as Bernard puts it. I twas an ominous
hint that researchers might have underestimated a future super-tsunami's
duration and potential punch.
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- How bad would a California tsunami be?
Certainly not as bad as the skyscraper-swallowing wave -- triggered by
a falling comet -- in this summer's blockbuster, "Deep Impact."
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- But a California tsunami could be pretty
bad, nonetheless.
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- The 15- to 20-foot-high tsunami in Crescent
City in 1964, triggered by a huge Alaska earthquake, killed11 and wrecked
30 city blocks.
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- "In 1812 in the Santa Barbara Channel,
there was a tsunami more than 8 feet high that hit fur-trading ships,"
Bernard said. "One was swept inland a quarter of a mile."
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- In 1994, Professor Kenji Satake of the
University of Michigan ran a computer simulation indicating that a magnitude-9
quake off the California-Oregon coast could send a 6-foot wave crashing
into Fort Point by the Golden Gate Bridge.
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- Catherine Firpo, emergency services coordinator
at the state Office of Emergency Services in Oakland, says the state's
tsunami mitigation effort is worth it: "Given the proximity of California
populations to coastal areas, it's not unreasonable to prepare to respond
to a coastal disaster such as this."
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- The California mapping program is led
by USC civil engineering Professor Costas E. Synolakis, who couldn't be
reached for comment. He has long warned that Californians might have under-rated
the tsunami risk.
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- In 1994, Synolakis suggested that offshore
thrust faults, which move vertically rather than horizontally, could trigger
a particularly severe tsunami. In a worst-case scenario, he and a colleague
said, a bizarre type of tsunami called a dipole wave -- generated just
off the Southern California coast -- might wreak even worse damage than
long-distance tsunamis.
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- Since NOAA is identifying the most vulnerable
West Coast sites, the scientists' first concern is towns and cities directly
on the coast, right in the face of an incoming wave.
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- "We (at NOAA) haven't done the study
for San Francisco yet -- but that's on our list," Bernard said.
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- He said that in all likelihood a major
tsunami entering the Bay "wouldn't propagate with a lot of speed --
but it would let a lot of water in," flooding low-lying areas in the
Bay Area.
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- The San Andreas Fault runs out to sea
just south of San Francisco .It is a kind of fault, known as strike-slip,
that is less likely to cause a tsunami, because it moves horizontally rather
than vertically. By contrast, major vertical faults exist off Los Angeles
and the Pacific Northwest.
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- Tsunami concerns also have risen because
of growing evidence that Pacific Northwest coastal quakes could be far
worse than previously imagined. Pacific Northwest mega-quakes occur every
several centuries, geological clues suggest.
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