Seems there’s been some shaking recently (Oct 2008) in the North Bend area. I also learned that the Seattle Fault line runs up under North Bend, and ends there.
Not to worry: “Big one” is expected.
me
Small Quakes Recorded in Snoqualmie Valley
SnoValley Star – October 22,2008
Right at 10:54 a.m. on Feb. 28, 2001, the Nisqually earthquake rattled the Puget Sound area, causing an estimated $2 to $4 billion in damages, and was responsible for one related death.
RIGHT: Heading into North Bend, Mt Si is a great backdrop for the town!
At the time, 34 North Bend residents reported feeling the quake, giving the temblor a VII, or “very strong” rating on the U.S. Geological Survey rating scale. Similarly, 27 Snoqualmie residents reported a similar shock, while 37 Issaquah respondents reported the quake as a VI, or “strong” event.
The Nisqually quake, rated a 6.8 magnitude earthquake, was centered 11.3 miles northeast of Olympia. According to geologists with the Pacific Northwest Seismic Network at the University of Washington, there is about an 84 percent chance of another Nisqually-type earthquake striking within the next 50 years.
Bill Steel, a PNSN spokesman, said the Puget Sound area is extremely active in terms of seismology due to a number of faults, plates and volcanoes in the area.
Running offshore, from about mid-Vancouver Island to Northern California, is the Cascadia Subduction Zone, which has historically released pressure in the form of 9-plus magnitude quakes every 500 years or so.
According to Steel, the last major Cascadia event occurred about 330 years ago – a magnitude temblor that created a tsunami that struck Japan. The quake and subsequent tsunami are well recorded in the oral traditions of local Indian tribes, Steel said.
The North Bend and Snoqualmie areas record numerous small “microquakes” that are the result of what Steel termed “crustal faults” that run from deep underground in the Puget Sound to the North Bend area.
Recent small quakes include a 1.6 magnitude event at 1:23 a.m. Sept. 26, centered just 2.2 miles northeast of North Bend. Another 1.6 quake was recorded at 6:58 p.m. Sept. 30, which was centered about 6 miles from North Bend.
“The North American Plate runs right under our feet and produces hundreds of earthquakes a year,” Steel said in a recent interview.
But for all the potential of another Nisqually or Cascadia-type quake, Steel said local earthquake experts fear most the potential damage that could be caused by an earthquake centered on the Seattle Fault, which runs right through Puget Sound, under Seattle, and stretches right to North Bend.
Although experts predict the likelihood of such a quake occurring in the next 50 years at about 5 percent, it represents the potentially most damaging threat to the Seattle area.
A group called the Earthquake Engineering Research Institute developed a study in 2005 that gives graphic detail about what could occur in the event of a 6.7 quake on the Seattle Fault (http://seattlescenario.eeri.org/).
According to that report, such a quake would cause an estimated $33 billion in damage – about 10 times that of the 2001 Nisqually quake – with a projected loss of life of as many as 1,600 people.
What would such a temblor feel like to Snoqualmie Valley residents?
Nothing at all, compared to what will occur in downtown Seattle and other heavily populated areas, where the scenario concludes that nearly 200,000 buildings will be seriously damaged or destroyed, and virtually every freeway rendered unusable.
“It would be a lot like the Nisqually,” Steel said of the North Bend and Snoqualmie experience, “largely because they’re far enough away from the rupture site. But if someone were looking in the right direction, they’d probably see the valley floor actually rolling as the quake approached. They’d actually see this.”
Such a quake, Steel said, would cause Snoqualmie and North Bend residents to “shake really hard. The trees would be rocking and rolling, but well-built structures should be alright.”
And, Steel said, all this would last for about 90 seconds.
“The important thing is people in Snoqualmie and North Bend are going to be isolated for awhile and need to be prepared for this. The King County Sheriff isn’t going to be of any help. None. They’re going to be too involved in other areas, and the roads and highways are going to be out,” Steel said.
Source Article: http://snovalleystar.com/2008/10/22/small-quakes-recorded-in-snoqualmie-valley
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