Risk of giant quake off American west coast goes up

[one...two...tree 2,762]

By Richard A. Lovett, Nature News

America's Pacific Northwest has a 37% chance of being hit by a magnitude 8 or larger earthquake in the next 50 years, a new study shows. That's more than double previous estimates of a 10-15% risk, says Chris Goldfinger, a marine geologist at Oregon State University in Corvallis.

In a monograph1 soon to be published by the US Geological Survey, Goldfinger and 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.

Using a combination of carbon-14 dating of trapped plankton and geophysical measures of the sediments' physical and magnetic characteristics, Goldfinger's team looked for landslides that appeared to have occurred simultaneously in numerous locations. "If we can link them together, a great earthquake is the most likely cause," Goldfinger says.

From the team's findings, he concludes that during the past 10,000 years -- the farthest back that the core samples allow him to peer -- the subduction zone has produced two types of earthquake. About half -- 19 by Goldfinger's count -- were megaquakes that rattled the entire region, producing magnitude-9 tremblers comparable to the one in the Indian Ocean that unleashed a devastating tsunami on 26 December 2004. Most of these had been discovered by other studies.

The other type, of which Goldfinger identified 22, affected only the southern portion of the fault zone, producing earthquakes of around magnitude 8. These earthquakes are smaller than the magnitude-9 megaquakes, but are still uncomfortably large. "These are similar to what took place in Chile" on 27 February 2010, he says.

Ticking time bomb

Previous hazard estimates, based on the magnitude-9 earthquakes, had set the recurrence interval for earthquakes in the region at about 500 years, with a 10-15% 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.

The last earthquake on the subduction zone was on 27 January 1700. Adding in the new earthquakes, and taking into account the statistical distribution of intervals between them, the next earthquake is overdue, and there's a 37% probability it will occur somewhere along the Cascadia fault in the next 50 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.

http://www.scientificamerican.com/article.cfm?id=risk-of-giant-quake-off-americ

[Obama 2012 1,714]

geologists/seismologists have been saying that the next big earthquake "due" is in the Seattle area and could be devastating more than any other location...

As much I keep waiting for the "left coast" of California to drop off into the ocean, I doubt it will be the next place to get a major earthquake.

That northwest region is quite active and quite due for something big.

[I AM NOT THAT GUY 5,715]

Must be Bush's fault (pun intended). I sure hope Obama will move quickly (another pun) to settle (still another) this issue as well.

Surprisingly quiet around that area.

Must be illegals tunneling again!

[Obama 2012 1,714]

Must be Bush's fault (pun intended). I sure hope Obama will move quickly (another pun) to settle (still another) this issue as well.

Must be illegals tunneling again!

[Darnell 8,478]

Nevada - the new Sea Coast state.

I'm looking forward to it!

However - I put no credence into any monograph that's chock full of scientific data - and neither should you.

[Nagishkaw 510]

And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.

Revelation 18:2