High magnitude earthquake risk on American west coast increases by 37pc.
Chris Goldfinger, a marine geologist at Oregon State University in Corvallis, along with his colleagues, examined more than 80 core samples taken from the seabed between Vancouver Island, in south-western Canada, and Cape Mendocino, in northern California, looking for deposits from submarine landslides triggered by massive earthquakes.
All the sample locations lay near the Cascadia subduction zone, a fault zone some 1,000 kilometres long that runs alongside the northwest American coast not far offshore, reports Nature.
According to the group's studies, the subduction zone has produced two types of earthquake. 19 of them were megaquakes of magnitude-9 - comparable to the one in the Indian Ocean that unleashed a devastating tsunami on 26 December 2004.
Other 22 affected only the southern portion of the fault zone, producing earthquakes of around magnitude 8.
"These are similar to what took place in Chile" on 27 February 2010, he says.
Previous hazard estimates had set the recurrence interval for earthquakes in the region at about 500 years, with a 10-15 per cent chance of another in the next 50 years. But Goldfinger's study, by upping the total number of earthquakes to 41, has cut the average recurrence interval to about 240 years.
"Public officials should maybe look at the new numbers and think about this earthquake as a real possibility in the next 50 years, instead of just a remote possibility," Goldfinger says.
The study is soon to be published by the US Geological Survey. (ANI)
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|Publication:||Asian News International|
|Date:||Jun 1, 2010|
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