Two small earthquakes shake the Valley
October 2, 2008 · Updated 4:55 PM
Two short, small earthquakes rattled the Valley last week.
Just before 11:30 a.m. on Thursday, Feb. 9, residents across the Valley felt a small, brief rumbling. According to the Pacific Northwest Seismograph Network (PNSN), that rumbling was a micro earthquake with a magnitude of 2.9. The quake was centered about two miles southwest of North Bend.
Then, at 3:48 a.m. on Saturday, Feb. 11, another 2.9-magnitude quake briefly rattled the Valley. That quake was centered about two miles south/southwest of North Bend.
According to Ruth Ludwin, research scientist with PNSN, earthquakes of this size near North Bend and Snoqualmie occur every few years or so. There was a 3.1-magnitude quake near North Bend on July 22, 2002, and a 3.5-magnitude quake occurred near Carnation on June 19, 2003. The 6.8-magnitude Nisqually quake on Feb. 28, 2001, with its epicenter near Olympia, was also felt across the Valley.
Ludwin said it is "quite unusual" to have two "felt" earthquakes in a week near North Bend, but added that research scientists don't know what that means in terms of the likelihood of a larger quake in the near future.
Ludwin said the largest quake in recent years near the area was the 5.3-magnitude Duvall earthquake on May 2, 1996. This quake was followed by hundreds of aftershocks and did some minor damage, she said.
For California, with a longer historic record and more frequent earthquakes, scientists have noticed that a moderately sized earthquake may be followed by a larger earthquake, she said. But larger earthquakes do not follow every moderately sized earthquake in California, and the Pacific Northwest may not have that pattern at all.
"A 2.9 is really very small, and we consider it 'background' seismicity - though it is a good reminder that large earthquakes do occur around here from time to time," she said.