SEATTLE -- A magnitude 4.6 earthquake shook Seattle and the Puget Sound region just before 3 a.m. local time Friday, according to the United States Geological Survey.
"It's been widely felt throughout the Seattle area," said Paul Caruso, a USGS geophysicist.
The shaking emanated from Three Lakes, Snohomish County, about nine miles east of downtown Everett. The earthquake was relatively shallow, originating about 14 miles beneath the surface, according to a USGS map.
There were no immediate reports of damage in Snohomish County, according to a tweet from the Sheriff's Office. Police in nearby Lake Stevens reported no damage to city infrastructure. The Washington State Department of Transportation said in a tweet that the agency would be inspecting bridges Friday morning, but had no reports of damage.
A second quake, measured at magnitude 3.5, was reported near Monroe a few minutes afterward. A handful of smaller aftershocks followed, according to the Pacific Northwest Seismic Network.
Initial USGS reports had described the larger trembling as a magnitude 4.4 earthquake that began less deep in the earth's surface.
Caruso said the earthquake was the product of a thrust fault, in which one side of a fault pushes upward in relation to its opposite side. Thrust faults are common in the Cascade Range, Caruso said.
He said the earthquake did not have any connection to recent tremors in California, and that it was too shallow to have originated in the Cascadia subduction zone off the Washington coast, where "stress and strain has been building for a long time."
Joan Gomberg, a USGS seismologist and affiliate faculty member at the University of Washington, said "the likelihood of a bigger one is small. It's not impossible, but it's small."
She said scientists were working Friday morning to better quantify those chances.