Here's a recent news article on those Spokane quakes - and of course more have just happened the last day or so...

Canie
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Wednesday, September 26, 2001

Spokane

Scientists assess earthquake risk to Spokane Temblor in 5 to 5.5 range a possibility, meeting told

Mike Prager - Staff writer

Scientists who study earthquakes in the Pacific Northwest said Tuesday that Spokane may be at some risk of a moderate temblor of magnitude 5.0 to 5.5.

Such an earthquake, if it occurred at a shallow depth, could crack pavement or break apart unreinforced brick walls.

Their assessment came during a community meeting at Garfield School on the North Side, not far from the epicenter of a magnitude 3.7 quake that struck the city on June 25 but caused little damage.

That temblor beneath Hamilton and North Foothills Drive was the strongest of 42 documented quakes along a swath from Gonzaga University to Five Mile.

No quakes have been recorded since Aug. 9.

Despite the summertime shaking, scientists said Spokane remains at low to moderate risk for a damaging earthquake.

''We have always viewed this as being very stable terrain,'' said Craig Weaver, of the Seattle field office of the U.S. Geological Survey.

He and other scientists are recommending more studies to gauge how much damage would occur if a moderately strong earthquake hit Spokane.

Weaver said the global forces that trigger large, damaging quakes are too distant to be a serious threat in Spokane.

Even so, seismic pressure being exerted by the Pacific plate along California and the Juan de Fuca plate along the Washington coast is putting stress on the adjacent North American plate, on which Spokane rests, and causing the bedrock here to fracture.

The Spokane quakes probably occurred in a series of ancient cracks in basalt layers underlying the city and involved volumes of rock no larger than a city block, Weaver said.

Fractures involving such relatively small amounts of rock cannot produce powerful quakes, the scientists said.

Ruth Ludwin, a researcher for the Pacific Northwest Seismograph Network at the University of Washington, reviewed data from five portable seismographs placed temporarily in Spokane during July.

She said the portable equipment confirmed what a lot of residents had been saying last summer. There were more earthquakes occurring than the network's online seismographs could measure.

Ludwin said the portable equipment sensed 14 previously undocumented quakes between July 1 and July 12. Of those, all but one was at a magnitude of less than 1.0.

That was no surprise to residents at the meeting.

''In my mind, I never thought of an earthquake being so noisy,'' said one man.

Weaver responded, ''When they are very shallow, that can happen.''