Science > Physics > 'Super-size our Tsunami Threat' for the West Coast
| Topic: |
Science > Physics |
| User: |
"Bunn E. Rabbit" |
| Date: |
27 Feb 2005 07:19:52 AM |
| Object: |
'Super-size our Tsunami Threat' for the West Coast |
Grab those adult diapers Primates!
--
Bunn E. Rabbit :)
"The same tectonic situation(Indonesia) exists just off the coastline
of Washington, Oregon and northern California.."
"...averaged about 80 feet above sea level, with "run-ups" on inland
slopes often reaching well over 100 feet."
SEATTLE POST-INTELLIGENCER
http://seattlepi.nwsource.com/local/211012_tsunamiscience07.html
New findings super-size our tsunami threat
80-foot waves blasted Indonesia, scientists now say
Monday, February 7, 2005
By TOM PAULSON
SEATTLE POST-INTELLIGENCER REPORTER
Scientists studying the Indian Ocean tsunami have discovered startling
evidence that the killer waves, at least for one coastal area in
northern Indonesia, were much larger than earlier believed.
The new findings, of keen interest worldwide to researchers seeking
insights into the mechanics of this disaster, also translate into a
disturbing suggestion that the experts have significantly
underestimated the magnitude of the tsunami threat in the Pacific
Northwest and perhaps to coastal communities around the Pacific Ocean.
"It's just staggering," said Andrew Moore, a scientist at Kent State
University who was on a research team, led by Yoshinobu Tsuji of the
University of Tokyo, that recently returned from studying the wave's
trail of destruction on the west coast of Sumatra.
Moore, Tsuji and their colleagues found preliminary evidence the
tsunami's height along an extensive section of shoreline south of the
city of Banda Aceh averaged about 80 feet above sea level, with
"run-ups" on inland slopes often reaching well over 100 feet. They
estimated the wave's average velocity on shore at 45 feet per second.
"It's mind-boggling to think about," said Vasily Titov, a
mathematician and tsunami computer modeler at the Pacific Marine
Environmental Laboratory in Seattle. The lab, operated by the National
Oceanic and Atmospheric Administration, is host to some of the world's
top tsunami scientists.
These findings, Titov said, will almost certainly prompt significant
revisions to basic theory and the tsunami models -- as well as a
serious upgrade in the predicted size of the tsunami expected from a
major quake off the coast of Washington and Oregon.
"Our worst-case scenario may not be the worst-case scenario,"
acknowledged Titov.
Most estimates of the Dec. 26 waves' maximum height above sea level
(sometimes referred to as "flow depth" to distinguish it from onshore
"run-up" heights) had put it at 30-35 feet -- primarily in parts of
Indonesia nearest the undersea earthquake.
Scientists studying the Indian Ocean tsunami, which killed at least
160,000 people, had heard the reports of higher waves -- of branches
and bark stripped off the first 80 feet of trees, of water marks and
roof damage found at or beyond the height of six- or seven-story
buildings -- but most figured these were the results of the wave
running up slopes or isolated instances of "focusing."
A tsunami wave can get "focused" or boosted suddenly in one location
as it comes on land by undersea canyons or other near-shore
geographical features or structures that squeeze the massive surge of
water into a narrower outlet -- much like a nozzle increases the force
of the water coming out of a hose.
But Moore said his team's wave-height measurements were consistent
over a long stretch of coastline and found well back from any slopes,
indicating these were direct measurements of the overall elevation of
this massive wall of water as it came on shore.
"It's just so far beyond what any of us have ever dealt with before,"
said Moore, who before moving East pursued tsunami research at the
University of Washington.
It's also way beyond the scope of what most of the experts have been
predicting will arise from the ocean depths the next time the Cascadia
Subduction Zone erupts.
The Cascadia zone, encompassing western Washington and Oregon, is
where two "tectonic" plates that make up the Earth's fractured crust
collide. The offshore Juan de Fuca Plate runs into and dives under, or
"subducts," the North American plate.
The plates move in a slow, subterranean collision at an average speed
of four centimeters per year. It wasn't until the mid-1990s that it
was widely recognized that Cascadia was an active subduction fault,
capable of producing the planet's most massive kind of earthquake,
centered some 100 miles offshore.
Since then, NOAA scientists have been working with the state
Department of Natural Resources and others to create "hazard maps"
that quantify the height and reach of a tsunami in certain communities
at highest risk.
But the maps are based on a tsunami with a maximum wave height of
about 30 feet.
"That was the best evidence available at the time," said Tim Walsh,
chief hazards geologist with the state agency.
"That's already a huge, incredibly destructive wave," noted Titov.
Until the Indian Ocean tsunami, he said, most experts would have
thought it absurd to suggest a tsunami with an overall wave height
greater than this.
But the tectonics of Cascadia and the undersea subduction fault near
Sumatra that spawned the Dec. 26 tsunami are alarmingly similar, Walsh
said. "We look a lot like the Indian Ocean," he said, which means they
may need to incorporate some new, bigger numbers in the hazard maps.
"Obviously, this has serious implications for all of the West Coast,"
said Harold Mofjeld, Titov's colleague and a senior tsunami researcher
at the NOAA lab. But such dramatic findings first must be confirmed
and considered in the light of alternative explanations, he said.
The shoreline could have dropped significantly in elevation during the
event, Mofjeld said, noting that this phenomenon of "subsidence" is
often associated with such large quakes. And there's still a
possibility the measurements by Tsuji and Moore were "disparities"
from large-scale focusing or some other cause, he said.
A British research ship, the HMS Scott, is conducting surveys of the
seafloor off Sumatra and has found evidence of massive submarine
landslides. Scientists say it's also possible these undersea
landslides magnified the waves.
Finding out just how similar, or different, Cascadia may be from
Sumatra will require a lot more detailed information about local
undersea canyons and other topographical features of the seafloor
(known as "bathymetry"), Walsh said. So far, he said, the bulk of
evidence indicates the similarities outnumber the differences.
"We need better bathymetry, and a lot of it is still classified
because of our submarines," said Walsh, referring to the deep-sea
traffic due to the U.S. Navy's Bangor submarine base headquartered
south of Bremerton.
Walsh would like to see the tsunami hazard mapping project shift to
getting better bathymetric and topographic data to "look for those
places that are particularly vulnerable" rather than to continue the
current approach of estimating the hazard community by community.
Another finding that may be of critical importance to communities
farther from the coast, on the Strait of Juan de Fuca and in Puget
Sound, was the Dec. 26 tsunami's ability to retain its force even when
going around corners. Scientists studying the waves' behavior in Sri
Lanka were stunned to see what happened on the leeward side of the
island nation.
"It was fairly large in many locations on the west side, bigger than
the numerical models predict," said Phil Liu, the Cornell University
scientist who led an American survey team in Sri Lanka.
Given all this flood of surprising information emerging from studies
of the Indian Ocean tsunami, Walsh said, officials may need to pursue
a different, more comprehensive strategy assessing and seeking to
mitigate the tsunami risk for the Pacific Coast.
A step in this direction locally may be taken later this week at a
meeting to be held in the high-risk southwestern Washington community
of Long Beach. The Coastal Tsunami Summit on Wednesday will feature
tsunami experts from NOAA, the Federal Emergency Management Agency,
the U.S. Geological Survey and several state agencies.
The meeting is intended to provide an overview of tsunami science,
methods of hazard assessment, discussions of evacuation plans and
warning systems and the National Tsunami Hazard Mitigation Program.
Though most of the new scientific findings are not on the meeting
agenda, the question will likely arise: Could Long Beach and other
Pacific Coast communities one day have to deal with a tsunami wave as
high as a six-story building?
"That's the sixty-million-dollar question," Walsh said.
COULD IT HAPPEN HERE?
LARGER WAVES DETECTED
Scientists studying the impact of the Dec. 26, 2004, tsunamis in
Sumatra have found evidence that they were much larger than earlier
estimates, in some cases two to three times larger. If these
preliminary findings are confirmed, experts may have to revise some of
their fundamental assumptions about these killer waves -- including
the level of threat in the Pacific Northwest.
SIMILAR CIRCUMSTANCES
The massive Indian Ocean tsunamis were spawned by an undersea
earthquake on a series of faults known as the Sumatran Subduction
Zone, where one of the Earth's massive tectonic plates known as the
Indo-Australian Plate collides with and then dives or "subducts" under
the South Asian Plate. The same tectonic situation exists just off the
coastline of Washington, Oregon and northern California and is called
the Cascadian Subduction Zone. Scientists are concerned that the same
kind of tsunami produced by the Sumatran fault could one day be
spawned by the Cascadian zone.
MORE INFORMATION
Pacific Marine Environmental Laboratory's tsunami research program:
www.pmel.noaa.gov/tsunami
Computer simulation of a tsunami generated by Cascadia mega-thrust
quake (original source, Kenji Satake, Geological Survey of Japan):
www.pgc.nrcan.gc.ca/press/images/2003JB002521-animation.gif
NOAA's simulation of Indonesian tsunami
www.pmel.noaa.gov/tsunami/Mov/TITOV-INDO2004.mov
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_____
"Cosmic upheaval is not so moving as a little child pondering the death
of a sparrow in the corner of a barn." -Anouk Aimee, French Actor
_____
"Death is better, a milder fate than tyranny", Aeschylus (525BC-456BC),
Agamemnon
_____
"I wear no Burka." - Mother Nature
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| User: "Halcitron" |
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| Title: Re: 'Super-size our Tsunami Threat' for the West Coast |
27 Feb 2005 02:10:25 PM |
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45 foot/second = 30.6818182 mile/hour (mph)
45 foot/second = 49.3776 kilometer/hour
A good bicycle speed, but I'd rather drive the truck.
:/
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| User: "Paul Silvers" |
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| Title: PROOF THAT LIBERALS ARE IDIOTS ==> 'Super-size our Tsunami Threat' for the West Coast |
27 Feb 2005 11:46:55 AM |
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On Sun, 27 Feb 2005 13:19:52 GMT, Bunn E. Rabbit
<BunnERabbit@verizon.hutch.net> wrote:
Grab those adult diapers Primates!
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