I slept through it. Did you feel it? At 5:25 am today (Friday) there was a moderate earthquake in the Puget Sound area, centered near Poulsbo, WA on the Kitsap peninsula. The USGS says it was a magnitude 4.5.
In my personal, Keith Seinfeld metrics, having lived for nine years in California, that qualifies as big enough to feel, and maybe enough to unnerve you. But, otherwise, pretty minor. Officially, it’s a “light” but “notable earthquake,” and the biggest we’ve had since a similar one on October 7th, 2006 (which was centered near Buckley, WA).
If you felt it, you can share your report here with the USGS (and see where the shaking was felt most strongly).
Coincidentally, the seismology team at the U.W. reported new details this week on “slow earthquakes” and “deep tremors.”
Seismologist Mario La Rocca and U.W. grad student Wendy McCausland placing a seismometer near Sequim in 2004. (La Rocca is an Italian geologist who works closely with the U.W.)
As I explained in my radio story, these are imperceptible quakes which recur on a fairly predictable cycle — every 15 months. The next one is due this summer, under the Olympic Peninsula.
The deep tremors and slow quakes are explained in this week’s journal Science. It appears they’re related to the Juan de Fuca plate subducting under the North American plate. Each slow quake adds a little more stress and strain to the major fault along the Washington coast. Every 500 years, roughly, that fault releases in a mega-thrust earthquake. Ken Creager at the U.W. says it seems possible or even likely that the next mega-quake will happen during one of the slow earthquakes.
Unfortunately, he can only test the theory after the Big One happens.