New breed of earthquake identified (MSNBC)

[eppur_se_muova]

‘Very low-frequency’ tremors may build up to catastrophic quakes

By Andrew Bridges
Updated: 2:29 p.m. ET Nov. 30, 2006

WASHINGTON - Japanese researchers have discovered a new and sluggish kind of seismic activity that helps reveal the inner workings of faults capable of producing massive earthquakes like the one that generated the 2004 Indian Ocean tsunami.

The so-called “very low-frequency” earthquakes join two other types of slow quakes previously detected in the deep portion of subduction zones, where one section of Earth’s crust dives under another. The new kind of seismic activity can itself produce earthquakes of magnitudes 3 to 3.5, but the temblors are too slow to produce shaking felt by humans.

Researcher Yoshihiro Ito said the newfound activity, along with the two other phenomena — non-volcanic deep tremors and slow slip — may contribute to the buildup of stress in what are known as megathrust quake rupture zones.

“We are considering the monitoring of these activities to have an accurate grasp of the stress condition for the megathrust rupture zone,” Ito said in an e-mail interview. Ito and colleagues from Japan’s National Research Institute for Earth Science and Disaster Prevention describe their work this week in Science Express, the online edition of the journal Science.

The snap release of slowly accumulated stresses in megathrust zones, like the Cascadia subduction zone in the Pacific Northwest, can produce massive earthquakes. The last such quake, a magnitude 9, struck that area in 1700.
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more: http://www.msnbc.msn.com/id/15971642/

[TechBear_Seattle]

1. As someone who lives in the Cascadia subduction zone...

:scared:

[Mythsaje]

2. Since there's nothing I can do about it

I just refuse to consider the possibility.

I think it's the only way to stay sane in the face of it.

[OneBlueSky]

3. maybe they should call them "earth rattles" . . . n/t

.