Slow Seismic Slip Event Underway in Pacific Northwest

www.livescience.com ^ | Updated 2:35 p.m. ET Sept. 14 -13 September 2005 | By Robert Roy Britt

[Esther Ruth]

rest of article...

The movement was predicted. Scientists recently learned that these ETS events recur about every 14 months. It has been detected by Global Positioning System instruments.

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Deadly Earthquakes

The event does not mean an earthquake is imminent, but geologists are eager to study it and learn more and they say sooner or later an ETS event is likely to trigger a major quake.

"Compared to the steady year-round stress accumulation, this more rapid stress increase implies that a large subduction earthquake is more likely to happen during the time of an ETS event," the Canadian geologists write.

The slippage and associated minor tremors "are directly related to megathrust (Sumatra-like) earthquake potential," lead geologist John Cassidy and a colleague said in Tuesday's statement. "Neither the tremor nor the slip can be felt."

Odds go up

The slip began Sept. 3 on the Olympic Peninsula of Washington State and has migrated north to the Vancouver Island area, Cassidy wrote. Victoria moved 0.12 inches (3 millimeters) to the West over the course of two days. The events are thought to last six to 15 days.

Cassidy's colleague, Stephane Mazzotti, has done some calculations on the odds of a large temblor.

"The probability of occurrence of a megathrust earthquake is about 30 times higher during this approximately two-week window, than during the rest of the 14.5 month cycle," Cassidy told LiveScience. "Having said that, 30 times a small number is still a small number."

Geologists simply don't know when one of these events will trigger a major quake, Cassidy said.

The immediate importance of the event is that it occurred as predicted and can now be used to improve understanding of the region's seismology.

"By better understanding these events, we will be able to better predict the effects (and perhaps timing) of future magnitude 9 earthquakes along the West Coast," Cassidy and his colleague write.

A separate study recently concluded that a major earthquake along the fault could be overdue, given clusters of the events seen in the geologic record. Because the fault is offshore, scientists say its rupture could create a devastating tsunami

[Peach]

hmmmm.

[Esther Ruth]

Drudge has this posted on his sight.

[coconutt2000]

If I remember correctly, the estimate of "every 500 years" is invalid. Averaging the estimated periods between the events doesn't mean anything when there is such a huge disparity between the longest known period between events and the shortest.

[Esther Ruth]

http://earthquake.usgs.gov/recenteqsww/Quakes/quakes_all.html

I haven't watched this for awhile so don't know if the activity by Mt St Helen is up or just same as usual.

[SpaceBar]

The value of 500 years was calculated by a moving temporal average of a poisson distribution written on a slip of paper and pulled out of a hat.

[DoughtyOne]

More evidence of global worming...

[Royal Wulff]

It runs in the reverse direction of the normal creep.

That sounds ridiculous. How are you going to stop a trillion tons of rock and make it suddenly move backwards?

[wyattearp]

More evidence of global worming...

Oh, that's bad...

[Snardius]

The chance of a major earthquake is 30 times higher now for a roughly two-week period

I'm not going to tell my wife about this...and if I time it just right, and the the earthquake does occur...[heh,heh]

[Leo Carpathian]

Another fault of Bush. He didn't sign the Koyote agreement!
Global warmint, Oz-one hole, Katerina, Tsunami, quakes....

[2nd Bn, 11th Mar]

More likely a PDOOMA.

Semper Fi,

[DoughtyOne]

Did kinda stink up the place didn't it. LOL

[USFRIENDINVICTORIA]

"How are you going to stop a trillion tons of rock and make it suddenly move backwards?"

Several trillion tons, I think. The Juan de Fuca plate is about 80,000 sq miles in area. A layer about 15 or 20 feet deep would weigh a trillion tons -- the plate is several miles thick. Large as it is, the plate is just a thin crust floating on the mantle and molten core.

When the "big one" hits, it won't be pretty. All of us living in the area are just playing the odds -- like people along the San Andreas fault are, or like people in New Orleans were.

[CCCnative]

More evidence of global worming...

How is that done?

[Ghost of Philip Marlowe]

And because they have information that dates only one prior event. That information is based upon core samples of cedar trees that were submerged after the last quake. The link between that and the great tsunami is largely anecdotal (journals of a Japanese emperor at the time that described the tsunami though it could have been caused by another undersea quake around the same time).

Once again, science is shaming itself by trying to establish trends based upon little precedence, as they are doing with global warming.

[Ghost of Philip Marlowe]

By the shifting of even greater magma forces that the trillion tons of rock are floating on.

I think this is going to happen and Seattle may well be obliterated. I really doubt anyone knows when it will happen, though.

[Ghost of Philip Marlowe]

Actually, the folks down in CA are pretty safe. The San Andreas down in CA is a side-slip (north and south movement) so it will never "break off."

That same fault runs through the middle of the Puget Sound, though. And there it changes to the "break off" type, one slipping under the other.

The greatest part of the danger is twofold. First, when it slipped last time it is estimated to have slipped about 5 feet. That's huge. Forces we couldn't even comprehend. The second part is that it is a very deep quake. It lasts for several minutes and commences a wave effect of the top layers. The quake we had a few years ago lasted less than a minute and was a quick, superficial jolt. We had lots of damage. Buildings that are earthquake-reinforced are designed to withstand such a quake. The Cascadia fault quake ("the big one") will set up a wave motion that will cause the buildings in Seattle to sway. Anything over a few floors will probably crumble and fall. The really tall ones (Columbia Tower) will probably snap low and fall like a Douglas Fir. I'm no expert on this subject. This is based upone what I have read about it. Any corrections/additions are welcome.

[sourcery]

Bush's Fault.

[Busywhiskers]

Well now...glad I am going to Idaho for the weekend just in case Oregon breaks off and falls into the Pacific.