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.
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
