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

Report: Only one use of excessive force upheld by Sheriff’s investigations in 2018

The Office of Law Enforcement Oversight has released its annual 2018 report.

King County Sheriff Department deputies searching the woods behind the Ten Trails housing development in Black Diamond for additional human remains. Photo by Ray Miller-Still
Human remains found in Black Diamond

The King County Sheriff’s Department is out searching for any additional remains near Ten Trails.

Cars on the lawn? That’s now a no-no in Covington

Covington City Council votes to approve a max number of vehicles, parking laws in residential zones

Dresses for a school full of royalty

PTA volunteers offer free homecoming, prom dresses to Tahoma, Kent students

New leaders, new space for the farmers market

Mark Hogen looks to help transition the Maple Valley Farmers Market to the Legacy Site

Local athlete takes bronze at Para-Pan American Games

Maple Valley’s Abbey Nardella already made her community proud by being accepted… Continue reading

Photo courtesy of the FARF 5k Superhero Run. Photos by Mark Mandi.
Capes, masks and running shoes

Capes, masks and running shoes

The Tahoma track team, with coach Jeff Brady in the bottom row on the left, after winning the 2019 state championship title. 
                                Photo courtesy of Jeff Brady. 
                                The entire Tahoma track and field, and cross country coaching staff. 
                                Photo courtesy of Jeff Brady.
Tahoma track stars and track coaches both share state titles

Coach Jeff Brady earns coach of the year for Washington state second year in a row

Parents successfully fight against ‘sexist’ dress code

Tahoma Schools approves new policy focused less on girls’ clothing

Most Read