August’s Episodic Tremor and Slip Now in Progress

Detail from PNSN’s tremor map

When I interviewed the UW’s Steve Malone back in May, he was looking ahead to this summer’s predicted episodic tremor and slip (ETS) event.

Now UW News says the seismic game is afoot once more:

The first ground motion associated with the event was recorded very early Sunday morning in an area north of Olympia and west of Tacoma. By Monday afternoon the signals were substantially stronger. If the event behaves like past occurrences, the source of the rumbling will move north through the Olympic Peninsula during the next week before crossing the Strait of Juan de Fuca to Canada’s Vancouver Island.

The seismologists at the Pacific Northwest Seismic Network have installed a huge “array of arrays” (eight arrays with ten seismic recording stations) that should help them “see” downward into the earth and triangulate on where exactly the ETS is emanating from. As I learned in the May interview:

What fascinates seismologists is that this kind of ETS event, in its slow-motion way, unleashes energy equivalent to a 6.5 magnitude quake or greater. It just does it with such nuance that no one noticed until recently.

Nuanced or not, this time the seismologists are dialed in. Hopefully we will soon know a little more about ETS and any connection if may have to our much-anticipated Big One. Scientists still don’t know exactly what is going on down there in the subduction zone–it’s not clear if the tremor and slip is relieving stress, adding to it, or simply moving it around.

3 thoughts on “August’s Episodic Tremor and Slip Now in Progress

  1. Or maybe not – this may be an instance of not being able to feel the earth move….

    You know the rest, as Steve Earle would say.

  2. I would like to be notified and follow the next ETS event, and any data that is generated by this study. This is so interesting! I was following it on its own website, but that was discontinued. According to my calculations, the next ETS is due in October 2012. Apparently the last one, August 2011 was early? Let me know if it is possible to grant my request. Thank you your attention. Nancy

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