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Researchers See Evidence Of Earthquake Fault In Spokane

Scientists who have been studying a swarm of small earthquakes that shook Spokane in 2001 say they may have evidence of a new fault in the area. 

On Friday, scientists from the U.S. Geological Survey announced an airborne survey of the Spokane area revealed clues that look to be connected to a so-called swarm of small earthquakes that struck in 2001.

The swarm was actually several small quakes, the largest of which registered a 4.0-magnitude quake on Nov. 11 of that year.

Richard Blakely of USGS says images from a satellite indicate an unusual ground deformation in north central Spokane.

“The ground bulged up. The bulge is about 1 to 2 miles across, and about half an inch high. Now, that sounds trivial unless you are a geologist. Then it’s pretty significant and unusual. The fact it corresponded with the earthquakes tells us the quakes and ground deformation were caused by the same thing, namely a fault,” Blakely said.

Last summer, an aircraft flying over Spokane conducting follow-up studies using magnetic sensors detected magnetic anomalies, one of which could be a fault. The anomaly seems to run parallel to the 2001 earthquakes.

Blakely says follow-up studies on the ground will determine whether the evidence really does indicate a fault. He says new guidelines for public safety may have to be put in to place if the evidence confirms their suspicions.

“Well, if we could prove that the fault was capable of producing magnitude size-6 earthquake, which I don’t think is out of the question, my recommendation would be of a campaign strap down their water heaters, bolt their house to the foundation, have an evacuation plan, that sort of thing,” he said.

Future studies will likely include excavating an area near the magnetic anomaly to determine if there is physical evidence of a fault line. 

Newspaper records indicate there was a series of small earthquakes in the 1920s in Spokane.