4.8 Earthquake Near San Juan Island was a SLOW SLIP EARTHQUAKE similiar to what occured prior to Japans 2011 earthquake.

[link to kuow.org]

4.8 Earthquake Near San Juan Island – Is 'Slow Slip' To Blame?

Thousands of people throughout the Puget Sound region felt a 4.8-magnitude earthquake Tuesday night centered between San Juan Island and Vancouver Island.

No major damage was reported, but seismologists are wondering about the role played by slow-slip tremors.

Slow slip is when the earth moves over several weeks, not in seconds as in an earthquake.

That happened right before the major 2011 earthquake off Japan, which caused a deadly tsunami and the Fukushima nuclear disaster.

John Vidale at the Pacific Northwest Seismic Network says there has been slow slip under Vancouver Island over the past week. He thinks it could have prompted the 4.8 quake.

"We wonder about that, since the slow slip does load the part of the subduction zone that we expect to deliver a magnitude 9 earthquake some day,” Vidale said. “But it's complicated, so it's something we're studying pretty carefully."