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

Mukilteo crabber missing; his boat was found at Hat Island

Frank Urbick set out Thursday morning but did not return.

Police looking for leads in case of missing Snohomish man

Henry John Groeneveld, 63, was last seen on Monday, when he said something about going to “the river.”

Separate Everett fires send man to hospital, damage boat

The man was hospitalized for smoke inhalation from the early morning fire.

Police: He made an appointment, then tried to rob the bank

A lawyer is accused of donning a fake beard and telling a teller that a gunman was outside.

Drive-by shooting reported in Marysville neighborhood

Police said there was no evidence to indicate it was targeted at a specific person or property.

Celebrating the origins of Christmas

LDS church holds annual nativity festival featuring more than 600 sets.

Trooper’s car struck when he was arresting man for DUI

She drove away but was arrested for investigation of driving under the influence and hit-and-run.

Inslee’s budget solves school funding with help from carbon

His budget would use reserves to boost education, then replenish them with a carbon tax or fee.

Man, 29, injured by shots fired at Everett thrift store

The gunfire followed an argument in the parking lot of Value Village on Evergreen Way.

Most Read