Quake-up call: 'Little red flags that the subduction zone is active'

Quake-up call: 'Little red flags that the subduction zone is active' »Play Video
Structures like the Coos Bay bridge are among the major infrastructure that will face risks when a subduction zone earthquake strikes the Pacific Northwest. (Photo by Lynn Ketchum, courtesy Oregon State University)

CORVALLIS, Ore. - The earthquakes felt along the North American west coast this week are essentially a warm-up act to a major subduction zone earthquake, seismologist Chris Goldfinger said.

“They're not directly leading to a giant earthquake, but little red flags that the subduction zone is active,” said the Oregon State University professor. “All of the North American plate is locked to this lower plate.”

Sunday night there was a 6.8 magnitude quake 50 miles west of Eureka, California. Thursday there was a 5.2 quake west of Gold Beach.

Professor Goldfinger is watching the activity of the lower Gorda tectonic plate closely, as it crunches and buckles against the North American plate.

“Think of it as clicks on a ratchet wrench, where you're tightening the system up and tightening it up and it's going click, click, click,” Goldfinger said, describing the seismic activity felt along the coastline.

He said we're not necessarily overdue for the next big earthquake, but we're smack in the middle of the time frame when something big might happen.

“When it happens, all of North America is going to jump to the west probably 15 to 20 meters in a matter of a minute and a half,” said Goldfinger.

Last year, authorities rolled out the Oregon Resilience Plan, which explained how we could best prepare for the worst case scenarios like a huge quake. Goldfinger said there's a lot of work to do, but there's still time.

“Don’t worry that anything is going to happen imminently from them, but take them as a reminder, just a message from the earth,” said Goldfinger.

Oregon Emergency Management is hosting a "Tsunami Road Show", or a series of earthquake and tsunami preparedness workshops along the coastal cities. Anyone interested in learning how they can better prepare for "The Big One" can stop in for safety tips and advice.

Friday,  March 14, North Bend 1:00 PM-3:00 PM Bay Area Community Health & Education Center  3950 Sherman Avenue  North Bend, OR

Monday,  March 17 Reedsport 1:00 PM-3:00 PM Lower Umpqua Hospital Conference Room  600 Ranch Road,  Reedsport, OR 97467

Tuesday,  March 18 Florence 9:00 AM-11:00 AM Siuslaw Fire and Rescue, Florence  2625 U.S. 101  Florence, OR 97439

Wednesday March 19 Newport 1:00 PM-3:00 PM Oregon Coast Community College  400 SE College Way,  Newport, OR 97366

Thursday,  March 20 Lincoln City 1:00 PM-3:00 PM Driftwood Library  801 U.S. 101 #201,  Lincoln City, OR 97367

Friday,  March 21 Tillamook 1:00 PM-3:00 PM Tillamook Library  1716 3rd Street  Tillamook, OR 97141

Wednesday  March 26 Seaside 1:00 PM-3:00 PM Providence Seaside Hospital,  Education Conference Room A  725 S. Wahanna Road,  Seaside, OR 97138

Thursday,  March 27 Astoria 1:00 PM-3:00 PM Judge Guy Boyington Building  857 Commercial,  Astoria, OR 97103


EUREKA, Calif. (AP) — One of the largest earthquakes to hit California in decades rattled the state's northern coast, but its depth and distance from shore reduced the impact on land, where there were no reports of injuries or damage, scientists and authorities said on Monday.

The magnitude-6.8 quake struck at 10:18 p.m. PDT Sunday and was centered 50 miles west of Eureka and about 10 miles beneath the Pacific seabed, according to the U.S. Geological Survey. It was initially reported as a magnitude-6.9, but later downgraded.

By late Monday morning, it had already produced 20 aftershocks of magnitude-3.5 or larger, and more were expected over the coming days, said Keith Knudsen, deputy director of the USGS's Earthquake Science Center in Menlo Park, Calif.

Knudsen said there was also a 5 to 10 percent chance of a larger quake in the area in the next week.

Sunday's quake was felt widely across the region, but both fire and sheriff's officials in Humboldt County said they had no reports of any damage or injuries. Humboldt County includes most of the populated areas closest to the epicenter.

"Everybody felt it region-wide to the point that there was concern for damage," said Humboldt County Sheriff's Lt. Steve Knight. But other than triggering some home alarms, the county escaped unharmed, he said. "We're very grateful."

There was no tsunami danger for the region as well, according to the National Tsunami Warning Center.

More than 3,000 people reported on the USGS website that they felt the quake within hours of it striking, including some across the border in Oregon.

"It was a big bump and then it rolled for about 30 seconds," said Diana Harralson, 64, who lives in an apartment in Rio Dell, about 55 miles southeast of the earthquake's epicenter. "It was a real good shaker."

Harralson said some knickknacks fell off the wall, but there was no damage. A California native who has experienced other earthquakes, she said she and her cat slept comfortably through the night.

Amandip Heer, a manager at a 76 Gas Station and convenience store in Eureka, described the quake as a "vibration," but said nothing fell off the shelves at the store, and there was no other damage.

Earthquakes are very common in Eureka, a city of about 27,000 people about 270 miles northwest of San Francisco and 100 miles south of the Oregon state line. Nearby Arcata is home to about 17,000 people and Humboldt State University.

Since 1980, there have been 10 earthquakes greater than magnitude-6 in the area, Knudsen said. California has experienced at least seven earthquakes of magnitude-6.9 over the same period, according to the USGS.

Sunday's quake was far enough from shore to allow much of its energy to dissipate, Knudsen said.

"We're fortunate it didn't strike closer to a populated area," he said.

An offshore earthquake of magnitude-7.2 about 30 miles southwest of Eureka in 1992 left 95 people injured and caused tens of millions of dollars in damage, according to the USGS. The earthquake was felt as far south as San Francisco.

It was followed by a magnitude-6.5 earthquake about 12 hours later and a magnitude-6.7 earthquake a few hours after that, both of which caused additional damage.

 

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