SPOKANE -- Recent earthquakes around the world are causing concern. Now scientists in the Northwest are monitoring whether the ground could start shaking in Spokane.
Nine years ago, the earth beneath Spokane started moving to the surprise of neighbors and experts. The series of quakes, called swarms, shook the Inland Northwest for months. Some of the quakes measured up to a magnitude 4.0. They also did damage by crumbling chimneys and cracking walls. Martha Calvert still remembers the one that brought down the siding on her house.
"I was in the shower and the house shook and made a big noise, of course, I didn't know what it was," said Calvert.
At first, scientists were stymied; there was no history of earthquakes rumbling in Spokane. In fact, there weren't even any seismographs to monitor an earthquake. But that has now changed. Ferris High School houses one of the main monitoring stations for the area. The seismograph sends data from Spokane all the way to the University of Washington and the Pacific Northwest Seismic Network.
After seismographs were installed, experts learned those swarms in 2001 were quite shallow and many of them were centered near Gonzaga Prep, in North Spokane. At first, scientists blamed the Latah Creek fault. But many experts now believe the quakes were not on a fault at all.
Volcanic rock formed over eastern Washington millions of years ago and it can become so brittle, it settles and breaks. Scientists think fracturing in the brittle ground caused the small earthquake swarms. But since 2001, the movement under Spokane has stopped.
Scientists believe those kinds of quakes could re-surface any time. But because they are not on a fault, they would likely top out around a magnitude 5.5, which would be quite significant. The most vulnerable would be un-reinforced brick and concrete buildings. Generally, those are buildings constructed before the 1970's.
