SEATTLE —A magnitude 4.6 earthquake shook Seattle and the Puget Sound region just before 3 a.m. 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 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 wrote 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 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.
The biggest fault near the earthquake is the Southern Whidbey Fault Line, but Gomberg said researchers don’t suspect this event occurred on that fault.
Scientists think another fault, further beneath the earth’s surface where scientists have less understanding, is likely responsible. That fault is probably not mapped and likely lacks surface expression features like cracks in the ground or offsets in topography that can be spotted with powerful lidar surveying technology, Gomberg said.
“If there’s earthquakes, there’s a fault,” Gomberg said. “There has been activity in this same spot.”
The larger earthquake was felt across the Canadian border, the USGS map reports. People reported feeling the earthquake to the south in Olympia, to the west in Port Angeles and to the east in Wenatchee.
Kieran Smith, 23, a Western Washington University student in Bellingham who lives in a fourth-floor apartment, said he felt his bed shake and the building sway.
On social media, many reported waking up or sensing the earthquake.
In Arlington, Tristan Halsen, 20, an Everett Community College student, was sitting on his couch working on homework when he heard a “really loud rumbling like a stampede,” he said in a Twitter message. A wall-mounted TV began shaking. At first, he thought it was a thunderstorm. Then, his house began shaking “for what seemed like forever,” he said.
“I think this was my first ‘big’ earthquake that I can remember and it was interesting to experience one this big,” he wrote.
Leah Kennebeck, who lives in Seattle’s Queen Anne neighborhood, said in a Twitter message that she woke up from a dream to her bed shaking and her ceiling light fixture rattling.
She “sat straight up and froze” trying to feel if the shaking was getting worse, she said.
“Once I realized things were rattling in my room longer than if it was from something like a truck going by, I knew it was an earthquake,” she said.