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Alaska tsunami
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A future earthquake off the coast of Alaska could unleash a devastating tsunami on ports and cities along the US Pacific coast, British scientists have warned.
Such an event could dwarf the great 1964 Alaskan earthquake, which triggered waves more than 40 feet high, research suggests.


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The potential for a huge Pacific Ocean tsunami on the West Coast of America may be greater than previously thought, according to a new study of geological evidence along the Gulf of Alaska coast.
The new research suggests that future tsunamis could reach a scale far beyond that suffered in the tsunami generated by the great 1964 Alaskan earthquake. Official figures put the number of deaths caused by the earthquake at around 130: 114 in Alaska and 16 in Oregon and California. The tsunami killed 35 people directly and caused extensive damage in Alaska, British Columbia, and the US Pacific region.
The 1964 Alaskan earthquake - the second biggest recorded in history with a magnitude of 9.2 - triggered a series of massive waves with run up heights of as much as 12.7 metres in the Alaskan Gulf region and 52 metres in the Shoup Bay submarine slide in Valdez Arm. 
The study suggests that rupture of an even larger area than the 1964 rupture zone could create an even bigger tsunami. Warning systems are in place on the west coast of North America but the findings suggest a need for a review of evacuation plans in the region.
The research team from Durham University in the UK, the University of Utah and Plafker Geohazard Consultants, gauged the extent of earthquakes over the last 2,000 years by studying subsoil samples and sediment sequences at sites along the Alaskan coast. The team radiocarbon-dated peat layers and sediments, and analysed the distribution of mud, sand and peat within them. The results suggest that earthquakes in the region may rupture even larger segments of the coast and sea floor than was previously thought.

Durham University

-- Edited by Blobrana on Monday 20th of July 2009 03:31:49 PM

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RE: Cascadia tsunamis
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Geologists now say there is a 10 to 14 percent chance of a major earthquake and tsunami hitting the Oregon Coast within the next 50 years, putting the coast through a disaster like that Hurricane Katrina brought in 2005 to the South.

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Oregon Quake
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A strong magnitude 6.4  earthquake occurred at 01:37:18 (UTC) on Thursday, January 10, 2008,  off the coast of Oregon region, 242 km  WNW  from Barview, at a depth of 10 km.

Location     43.883°N, 127.228°W


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Vancouver Island quake
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Perhaps it was just a matter of sympathy, but tremors rippled the landscape of Vancouver Island, the westernmost part of British Columbia, in 2002 during a major Alaskan earthquake. Geoscientists at the University of Washington have found clear evidence that the two events were related.
Tremor episodes have long been observed near volcanoes and more recently around subduction zones, regions where the Earth's tectonic plates are shifting so that one slides beneath another. Tremors in subduction zones are associated with slow-slip events in which energy equivalent to a moderate-sized earthquake is released in days or weeks, rather than seconds.
Now researchers studying seismograph records have pinpointed five tremor bursts on Vancouver Island on Nov. 3, 2002, the result of a magnitude 7.8 earthquake on the Denali fault in the heart of Alaska.
As surface waves, called Love waves, shook Vancouver Island they triggered tremors underneath the island in the subduction zone where the Explorer tectonic plate slides beneath the North American plate. The tremors were measured by seismometers along roughly the northern two-thirds of the island.
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Cascadia tsunamis
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Tales about "Thunderbird" and "Whale" by native tribes along the U.S. West Coast, along with geological clues, point to at least two massive quakes and tsunamis that have hit the area in the last 1,100 years.

"Native people here were well aware that earthquakes happened and that is reflected in their oral traditions" - Ruth Ludwin, a University of Washington researcher who recently published two papers detailing such folklore.

In one tale, the mythical wind creature "Thunderbird" drives its talons into "Whale's" back and is dragged to the bottom of the ocean, which she said could be interpreted as a tsunami-like event.

"There was a shaking, jumping up and trembling of the earth beneath, and a rolling up of the great waters"

So says an ancient tale told to generations of Quilleute and Hoh Indians. Variations of this saga of an epic battle between the Thunderbird and the Whale are found among Pacific Northwest Tribes from Vancouver Island to Oregon's Tillamook tribe.
It's clear now that the stories document a massive earthquake and tsunami that hit the Northwest before the arrival of European settlers.


Many Pacific Northwest tribes depict an epic battle between a thunderbird and a whale that scientists believe describe a massive earthquake and tsunami. A Quileute drawing includes a waxing moon in the centre, which would coincide with the lunar phase on the night of the Cascadia quake of Jan. 27, 1700

The stories were collected from native tribes in northern California, Oregon, Washington and just south of Canada's Vancouver Island.
Ludwin, who collaborated with seismologists, said she began looking into the region's "geomythology" six years ago because of the lack of such data, which can be found in other areas such as Japan and the Indonesian island of Sumatra.

In December, a 9.15 magnitude earthquake erupted off the coast of Indonesia's Sumatra island. The quake, the strongest in 40 years, sent walls of water as high as 33 feet barrelling into 13 Indian Ocean nations and killed 160,000 people.
Last month, a major 7.0 magnitude earthquake off the coast of northern California triggered tsunami alerts along most of the U.S. West Coast. The alarm was quickly called off and there were no casualties or damage.



The Cascadia subduction zone, which generates much of the seismic activity in the Pacific Northwest, had at least seven major earthquakes in the last 3,500 years, according to researchers.
One massive earthquake is estimated to have hit the region in 900, while eyewitness accounts from the 19th century point to a huge earthquake and tsunami that hit the area in 1700.

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