Earlier quake didn’t trigger landslide, USGS says

OSO — A small earthquake on March 10 did not trigger Saturday’s deadly landslide, according to the U.S. Geological Survey.

Snohomish County officials raised questions on Tuesday whether a quake may have contributed to the hillside breaking free and crashing across the valley.

The slide has killed at least 25 people. In all, 90 people are officially considered missing. The debris field covers one square mile and is 50 feet deep in places.

“That earthquake was too small, too weak to account for the slide,” Craig Weaver with the USGS said Thursday.

The slide earlier this month measured 1.1 magnitude.

Seismic activity shows that there were two large slides on Saturday with the first hitting at 10:37 a.m. A second, larger mass crashed down around 10:41 a.m.

The readings, taken at the University of Washington, show the land moving for more than an hour.

Meanwhile, a report released Thursday by the USGS shows a long history of slides in the North Fork Stillaguamish River valley around Oso, including one slide that had a debris field nearly twice as big as the Oso landslide.

Geologists can tell the ancient slide was huge, but “I can’t tell you how quickly it came down, whether it took weeks or seconds,” said Ralph Haugerud, a USGS geologist and the report’s author.

The ancient slide occurred less than a mile west of the hillside that collapsed. It created a debris field more than a mile wide just north of where the Stilly runs today.

A map with the report shows a river valley lined by ancient landslides, all of which occurred since the last ice age. The slides might have also covered up earlier ones, the report notes.

More in Local News

‘Come talk to me. Don’t jump, come talk to me’

State Patrol trooper Yaroslav Holodkov just happened to be driving by when he saw a suicidal man.

Marysville educators reach out to a newly traumatized school

Several affected by shootings in 2014 offered to talk with counterparts in Eastern Washington.

Hurry! Target will take your old car seat, but not for long

The seats will be taken apart and the various materials recycled.

Sheriff’s Office receives national recognition

Sheriff accepts award “notable achievements in the field of highway safety” over the past year.

Edmonds-Woodway High School briefly locked down

A student tried to stop a fight and a boy, 16, responded by threatening the student with a knife.

Study considers making it legal to grow marijuana at home

The Liquor and Cannabis Board is considering two scenarios for allowing a minimal number of plants.

Minutes mattered the day Pat Ward was brought back to life

The Mukilteo police and fire chaplain died at breakfast. She got a second chance thanks to a waitress.

Marysville babysitter found guilty of infant girl’s death

Medical experts differed over whether it was head trauma or illness that caused the baby to die.

Whether cheers or jeers, DeVos appearance will rouse spirits

Trump’s secretary of education is coming to Bellevue to raise money for a pro-business think tank.

Most Read