The quake was caused by slipping along an offshore fault called the Blanco Fracture Zone and has nothing to do with the more well-known Cascadia fault, which is believed to be overdue for a major earthquake in the Pacific Northwest, said Paul Bodin, manager of the Pacific Northwest Seismic Network at the University of Washington.
The event is also unrelated to a cluster of "episodic slips" along the Cascadia tectonic plate boundary that have been releasing energy across the coastal Pacific Northwest over the past week to 10 days, he said.
Those slips are not felt by humans but have been picked up by monitoring devices around the Olympic Peninsula in northwest Washington state and also stretching from Eugene to the Siskiyou Mountains along the Oregon-California border, according to the Pacific Northwest Seismic Network.
The slips along the Cascadia relented two days ago after a fairly active week, Bodin said. "Who knows what Mother Earth is trying to tell us, but as far as we know, the earthquake today is ... at a very unsurprising place," he said.