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Posted on 10/28/2002 4:27:53 PM PST by blam
Researchers plot course of ancient American tsunami
Researchers have calculated the scale of a giant wave that devastated the north west coast of America 1,100 years ago.
Japanese scientists used computer modelling to recreate the devastation from the ancient tsunami.
The team from the Disaster Reduction and Human Renovation Institution in Kobe say the work will help planners minimise the impact of any future wave.
The researchers took clues from silt deposits found in the Puget Sound, a Pacific inlet above earthquake fault lines in the Seattle area.
Experts say the tsunami could have reached up to seven metres in height and penetrated 300 metres inland.
They say it's possible a tsunami of similar scale could hit the Puget Sound in the event of a future quake.
Nature says that the research will be incorporated into maps predicting the areas most at risk.
Story filed: 11:06 Monday 28th October 2002
North of the rapids on the Brazos river, I trust? (They were formed 65 mya by the impact tsunami from the strike at Chicxulub that wiped out the dinosaurs)...
Here you go:
Tree-ring study enables researchers to link massive American earthquake to Japanese tsunami in January 1700
Stumps of long-dead western red cedar trees are revealing new details of a cataclysmic earthquake along North America's west coast more than 100 years before the arrival of the first European occupants.
Two University of Washington researchers believe that evidence in the dead wood confirms that in the year 1700 a great earthquake struck the Pacific Northwest coast and set off a tsunami, a train of massive ocean waves, that flooded coastal Japan.
The scientists are reporting in tomorrow's Nature magazine (Oct. 30) that they have dated the demise of six trees, along 60 miles of the Washington coast, by "reading" the annual ring patterns in the trunks and roots of the stumps. They found that each of the trees produced its final ring in the 1699 growing season. No further rings were evident, indicating that the trees were dead by the spring of 1700.
"We are saying this huge earthquake really happened," says David Yamaguchi, a UW dendrochronologist, or tree-ring analyst. Last year Japanese scientists reported that a tsunami that hit Honshu island on January 27, 1700, was probably caused by an earthquake on the Cascadia subduction zone, a 600-mile coastal fault stretching from British Columbia to northern California.
Based on the size of the tsunami, the Japanese researchers estimated the earthquake at magnitude 9, even though no Cascadia fault earthquake of magnitude 5 or above has ever been recorded by seismologists. The Nature article concludes that the tree dates "mean that the northwestern United States and adjacent Canada are plausibly subject to earthquakes of magnitude 9."
The second author of the paper, Brian Atwater of the U.S. Geological Survey and an affiliate UW professor, says the new dates clinch the argument that massive earthquakes can occur where the Juan de Fuca plate, an Oregon-sized slab of crust, collides with a large block of continental crust called the North America plate. The Cascadia fault forms the boundary between the two plates.
Over the past decade, Atwater and other researchers have discovered geologic evidence of repeated magnitude 8 or larger earthquakes along the Cascadia fault. However, the size of the 1700 earthquake remains a subject of much debate, which the tree-ring dates do not resolve, says Atwater. Some scientists have proposed a ceiling of magnitude 8; others have suggested a maximum magnitude of 9.5.
Only a handful of magnitude 9 earthquakes have occurred globally this century. The largest earthquake in the Pacific Northwest in historic times was a magnitude 7.4 in the north Cascade mountains in 1872. This was not on the Cascadia fault.
Yamaguchi first "read" the cedar stumps to show that a great earthquake happened some time after 1690. UW researcher Minze Stuiver then pinned the earthquake to between 1695 and 1710 with precise radiocarbon dating. This led the Japanese scientists to propose the Cascadia fault as the likely origin for the 1700 tsunami.
To test the Japanese theory, the UW researchers dug up the roots of a dozen cedar stumps from the Copalis River south to the Columbia River. In half of these stumps, the dating was inconclusive, but in six they found evidence that the trees had died before the start of the 1700 growing season.
Then they all moved to Columbus and founded Ohio State...
(grin) Go Blue!
Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)
Channeled Scablands Theory
http://www.spokaneoutdoors.com/scabland.htm
But this one only came in about a 1000 feet.
Now that we have seen an actual major tsunami, it seems Fairbanks would be safe even if it were a foot above mean high tide.
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| GGG managers are SunkenCiv, StayAt HomeMother & Ernest_at_the_Beach | |
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Just updating the GGG info, not sending a general distribution. |
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Note: this topic is from 10/28/2002. Thanks blam.
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