4.6 earthquake strikes north of Seattle

A 4.6 magnitude earthquake shook the Puget Sound region early Friday.

The quake was centered in Monroe, east of Everett, according to the U.S. Geological Survey's earthquake mapping system.

The quake occurred about 24 kilometers deep at 2:51 a.m., the USGS said. The initial magnitude was 4.7, but that number was adjusted down to 4.6. A smaller 3.5 tremor hit minutes later.

The shaking was felt across the region. The USGS received reports from as far north as Vancouver, British Columbia, to the east in Wenatchee and south to Yakima. No damage was initially reported.

Seana Mattison works at the 76 station on U.S. 2 just west of the epicenter. She was getting ready for work at her home a couple blocks away when the earthquake struck.

"It felt like an explosion," she said. "And the guy who was working here, he said that's what he felt too. It was almost like you could hear the boom."

In the Seattle suburb of Brier in south Snohomish County, about 14 miles from the epicenter, the rocking was enough to wake people up. Dogs began howling.

"It felt like a jolt up and down sensation ... like my house was trying to lift off its foundation," said Ni Cushmeer of Mill Creek, which is about 10 miles from Monroe.

KUOW reporter Casey Martin, who lives in Kirkland, said the earthquake "started with a solid thud then wiggled for about 15 seconds. My old house creaked like mad."

Maria Keene of Mountlake Terrace said she woke to the shaking.

"I thought I was dreaming, but then I went to my sister and she woke up too and she said she felt it too," Keene said.

Twitter lit up with reports of people feeling the tremors.

Here's a tighter look at the epicenter from the USGS. It's right at the western edge of Monroe, adjacent to the Evergreen State Fairgrounds along U.S. 2. That's a main route from western Washington to the eastern part of the state, and a major train track also runs in that corridor.

Traffic appeared to be unaffected, but the state Department of Transportation tweeted that it would be inspecting bridges in the area on Friday.

Bill Steele, the seismology lab coordinator at the Pacific Northwest Seismic Network at the University of Washington, said source of the earthquake is not related to the Cascadia subduction zone -- that's the major fault that seismologists fear could produce a major quake.

He said you can kind of blame California for this quake in the North American crust.

“It’s more related to California being dragged north and pressing up against the buttress of British Columbia," Steele said. "So it’s kind of a compressive earthquake that allows shortening between Seattle and Vancouver, B.C.”