An aerial photo shows the locations of two earthquakes and five aftershocks in and near Monroe, which rattled the Puget Sound region early Friday. The first was the magnitude 4.6 quake at upper right, 13 miles under the intersection of U.S. 2 and Fryelands Boulevard SE at 2:51 a.m. The second, magnitude 3.5, occurred 18 miles under the Old Snohomish-Monroe Road at 2:53 a.m. The aftershocks followed during the ensuing two hours. This image depicts an area about 3 miles wide. (Herald staff and the Pacific Northwest Seismic Network)

An aerial photo shows the locations of two earthquakes and five aftershocks in and near Monroe, which rattled the Puget Sound region early Friday. The first was the magnitude 4.6 quake at upper right, 13 miles under the intersection of U.S. 2 and Fryelands Boulevard SE at 2:51 a.m. The second, magnitude 3.5, occurred 18 miles under the Old Snohomish-Monroe Road at 2:53 a.m. The aftershocks followed during the ensuing two hours. This image depicts an area about 3 miles wide. (Herald staff and the Pacific Northwest Seismic Network)

Early wake-up call: Twin quakes under Monroe rattle region

Thousands of people felt them. They were magnitude 4.6 and 3.5 and hit minutes apart.

MONROE — Thousands of Puget Sound-area residents were shaken awake early Friday as twin earthquakes hit the region, minutes apart and centered under Monroe, according to the U.S. Geological Survey.

The first quake, magnitude 4.6 and 13½ miles deep, hit at 2:51 a.m. A second one two minutes later was magnitude 3.5 and 18 miles deep. The first of at least five aftershocks followed at 2:56 a.m. Over the next couple of hours, they ranged from 1.7 to 0.9.

The Snohomish County Sheriff’s Office and other government agencies said there were no reports of damage, and the quakes did not pose a tsunami threat, according to a tweet by the U.S. National Tsunami Warning Center. However, the Snohomish County Public Utility District reported that some customers in the area lost power. Electricity was restored to most within a couple of hours.

The shaking awakened people as far away as Seattle. A USGS intensity map suggested the earthquakes could be felt as far south as Olympia and as far north as Vancouver, British Columbia.

Officials were soliciting reports from those who felt the shaking. By 7 a.m., more than 6,000 people had submitted reports to the U.S. Geological Survey to document the effects.

In an email, a Mukilteo resident described how it felt to him: “Awakened by low rumble. As I became awake, the house shook horizontally back and forth a couple of times, the quake being like a ripple on water, traveling through the ground. Eerie feeling — the shaking didn’t wake me, it was the sound. As the shaking stopped I could faintly hear the sound of the quake as the shock wave traveled on.”

A U.S. Geological Survey depiction of the shaking caused by a magnitude 4.6 earthquake at 2:51 a.m. Friday under Monroe. (USGS)

A U.S. Geological Survey depiction of the shaking caused by a magnitude 4.6 earthquake at 2:51 a.m. Friday under Monroe. (USGS)

The low rumble was also heard in Everett, where the shake rattled buildings side to side. The second tremor was softer and shorter.

In Seattle, the quake could be felt as a gentle rocking.

The first quake originated 13 miles under the intersection of Fryelands Boulevard SE and U.S. 2 on the east side of Monroe, according to a USGS map.

The epicenter of the second one was about a mile or so southwest of there, east of the city and focused 18 miles under the Old Snohomish-Monroe Road.

Smaller quakes like the ones Friday are not unusual in this area. And there have been bigger ones over the decades.

A 2012 Herald story reported that since 1900, six earthquakes of magnitude 5.0 or greater have been recorded as having caused damage in Snohomish and Island counties, or were centered within the counties’ borders.

Two significant faults run through Snohomish and Island counties. The South Whidbey Island Fault Zone consists of several intermittent faults that run from the Strait of Juan de Fuca southeast across Whidbey Island and south Snohomish County to Woodinville. The Devils Mountain Fault runs from the Strait of Juan de Fuca east near Deception Pass and across the Skagit-Snohomish county line southeast to Darrington.

Geologic evidence shows that large quakes have happened in the South Whidbey and Devils Mountain fault zones in the distant past. One happened in 1950 in the South Whidbey fault zone but data were inconclusive about the fault of origin, according to the University of Washington Seismology Lab.

Quakes on those faults carry a potential magnitude of 7.5, which could cause severe damage because of their proximity to the surface, according to a natural hazard report done for Snohomish County in 2010.

A possibly more serious threat is a quake in the Cascadia Subduction Zone 50 miles off the Pacific coast, which could inflict a quake of up to 9.5 in magnitude, causing catastrophic damage and capable of starting a tsunami.

Information from The Daily Herald’s archive is included in this story.

More online

Pacific Northwest Seismic Network

U.S. Geological Survey

Washington Geological Survey

More in News & Comment

Former pastor pleads guilty in theft of Oso slide donations

Gary J. Ray admitted he took at least $10,000 intended for families affected by the 2014 disaster.

Governments, transit agencies sue to block car-tab measure

They claim I-976 is unconstitutionally broad. Tim Eyman calls the litigation a “slap in the face” of voters.

Paige Mino, a seasonal research assistant for the Hawaiian Monk Seal Research Program on Oahu, found a message in a bottle off of Bird Island. The message was from a North Bend Elementary kindergarten class from 1998. Photo courtesy of Paige Mino
Message in a bottle found 21 years later

The bottle traveled over 3,000 miles; found off the coast of Bird Island 21 years later.

Kent’s ShoWare Center losses hit $852K through third quarter

Arena trying to recover from rough start to 2019

A King County judge found the company misled customers into thinking it was a charity. Photo courtesy of the state Attorney General’s office
Judge rules Value Village deceived customers

The King County judge found the company misled customers into thinking it was a charity.

Want to see UFOs? Washington is a popular hangout

Our state is third in nation for alien craft encounters. UFOiTeam says it’s nothing to snicker about.

King County will challenge legality of I-976

County Executive Dow Constantine: ‘We must clean up another mess that Tim Eyman has created for our state, our region, and our economy’

King County Council
King County Council incumbents ahead, with the exception of Gossett

Preliminary results are in for the King County Council races.

Voters are narrowly rejecting affirmative action

The no camp on affirmative action is winning by just over one point.

I-976 is passing, worrying transit advocates

The initiative promises $30 car tabs, but opponents say it will destroy state transit infrastructure.

Vehicles passing through flooded street. File photo
King County Flood Control District to vote on 2020 budget

The budget will fund a variety of programs across the county.

Washington State Ferries plans for an electric-hybrid fleet

It will be a literal sea change for the nation’s biggest system — and a technically ambitious one.