Slow Earthquake Begins in Washington

"Slow earthquakes" are officially known as Episodic Tremor and Slip (ETS) events. They release as much energy as the usual kind of earthquake, but they take weeks to do so. They were invisible to seismologists until just a few years ago, and now a new event has begun under western Washington, according to the Pacific Northwest Seismic Network's Deep Tremor News page. Researchers have considered it several months overdue, as previous ETS events have occurred at roughly 14-month intervals. They take place along the subduction zone beneath the Seattle/Puget Sound area, below the depth where the colliding Pacific and North American plates are locked together. Click to the main tremor index page for more background. The Kitsap Sun has picked up on the story, too.