An earthquake of magnitude 5.5 struck off the Washington coast Saturday night, followed by at least 10 small aftershocks, according to the Pacific Northwest Seismic Network at the University of Washington.
There was no threat of a tsunami.
“Quakes like this tend to come in sequences,” said PNSN Director John Vidale. “Most likely we’ve seen the biggest event we’re going to see.”
The quakes were clustered about 180 miles west of Neah Bay. They occurred along an underwater ridge where molten rock from deep in the earth is welling up and creating new sea floor. Quakes are common in the area, Vidale said. The sequence of shocks is unlikely to escalate or trigger a quake on the Cascadia Subduction Zone, the place where the ocean floor dives under the continent.
The biggest quake hit at about 11:07 p.m., followed by aftershocks of magnitude 3.1 and 4.5 shortly after midnight and around 1 a.m. There were several other smaller shocks, Vidale said.
“Sequences like this sometimes last for days,” he said.
A few people reported feeling the biggest quake.