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.