Seismic fault beneath us is ‘fully loaded’ after 311 years

  • By Julie Muhlstein Herald Columnist
  • Wednesday, January 26, 2011 12:01am
  • Local News

As if you didn’t have enough worries, here is one more to add to that massive list:

“It’s been 300 years,” Bill Steele said Tuesday. “We have a fully loaded subduction zone.”

Actually, it’s been 311 years since the Great Cascadia Earthquake of

1700.

Steele, a University of Washington seismologist and spokesman for the Pacific Northwest Seismic Network, said scientists have determined the monster quake occurred Jan. 26, 1700 — 311 years ago tonight.

It happened off the Northwest coast, and created huge tsunamis that devastated shorelines here and in Japan.

What’s amazing is how much is known, considering that in 1700 there were no Europeans in the Northwest. British Capt. George Vancouver wouldn’t find his way here until 1792. The Lewis and Clark Expedition to the West didn’t start until 1804. Historians have no original account of the 1700 quake written from a Western perspective.

“There’s quite a detective story of how we know all that. It’s fantastic,” Steele said.

First, a quick explanation of what happened from the online encyclopedia HistoryLink:

“The earthquake ruptured what is known as the Cascadia subduction zone — the area of overlap between two of the tectonic plates that make up the Earth’s surface, the Juan de Fuca plate and the North American plate.” The 2003 HistoryLink essay by Greg Lange, citing scientists who studied the quake, said the event dropped the whole Pacific Northwest coastline 3 to 6 feet, and that the tsunami was as high as 33 feet.

Knowledge of all that comes from both recent science and long-ago legends and tales of American Indians. Ruth Ludwin, a former University of Washington geophysics professor, has studied and published evidence of the quake found in native lore, Steele said.

“There are a large number of Native American legends and tales of meadows reclaimed by the sea, of great shaking and landslides, and of whole villages wiped out with canoes found in the trees,” he said. “It may have killed tens of thousands of people, but there is no written record of that.”

Scientific evidence of the 1700 earthquake comes from Dr. Brian Atwater of the U.S. Geological Survey, Japan’s Kenji Satake and other researchers. Their work identifying “ghost forests” and an “orphan tsunami” is no less compelling than the Native legends.

“Brian Atwater uncovered a layer cake of soils,” Steele said. At Willapa Bay on the southwest Washington coast, he said, there are five layers where scientists see transitions from marshy tidal estuary to woody soil, indicating trees, all covered by layers of sand and bay mud.

The layers show places where land levels rapidly changed. And studies of the roots of trees in what Steele called “ghost forests” showed that trees died between the growing season of 1699 and before their sap would have come in 1700.

Steele said Kenji Satake, of the Geological Survey of Japan, found records of samurai lords, who kept track of rice harvests. Those detailed records, Steele said, showed that an “orphan tsunami” — a giant wave without any shaking in the area — hit the coast of Japan on Jan. 27, 1700. “It did kill a number of people in Japan,” Steele said.

By working with those records and wave speed, he said, scientists determined that the quake hit the Northwest coast about 9 p.m. Jan. 26, 1700.

“It’s quite a marvelous story, what happened and the impact. No one wrote about it in the West,” he said.

It’s fascinating, but frightening, too.

Steele said it takes hundreds of years to build up the strain that causes a subduction zone earthquake. “The toe of North America, the edge, is being shoved downward. It’s like bending a ruler back,” he said, adding that the 1700 quake was the last one known to have occurred on the Cascadia subduction zone.

Remember — it’s “fully loaded.”

“It could produce another one tomorrow, or maybe a century or more away,” Steele said. “Certainly geologically, in the not too distant future we’re going to have another one.”

Steele is all for being prepared — whether it’s keeping supplies on hand at home, making sure homes and public buildings are up to withstanding big quakes, or assuring that people who live on the coast have evacuation routes.

It takes money, and recognizing the risks.

“Our purpose here is not to scare people,” Steele said.

Julie Muhlstein: 425-339-3460, muhlstein@heraldnet.com.

Talk to us

More in Local News

Logo for news use featuring the municipality of Lake Stevens in Snohomish County, Washington. 220118
Motorcyclist identified in fatal crash near Lake Stevens

Anthony Palko, 33, died Monday night after colliding with a passenger car. The juveniles in the car were taken to the hospital.

Marysville
Police: Marysville man shot sword-wielding roommate in self-defense

The roommates were arguing over eBay sales, according to police. Then one of them allegedly brandished a two-foot sword.

Logo for news use featuring the municipality of Lake Stevens in Snohomish County, Washington. 220118
Everett boy, 12, identified as Davies Beach drowning victim

Malachi Bell was one of three swimmers in distress Sunday in Lake Stevens. He did not survive.

Everett
Port of Everett hosting annual open house after pandemic hiatus

Also, Rustic Cork Wine Bar plans to open a second shop at Fisherman’s Harbor — the latest addition to the port’s “wine walk.”

Mike Kersey with Aiya Moore, daughter of Christina Anderson, right, talk about the condition of Nick’s Place in Everett, Washington on June 17, 2022.  (Kevin Clark / The Herald)
‘We’re all good people when we get clean and sober’

Who has fentanyl taken from us? A messenger who saved lives. A “street mom.” A grandpa who loved his grandkids “999 trillion times.”

Snohomish County Superior Courthouse in Everett, Washington on February 8, 2022.  (Kevin Clark / The Herald)
Bailiff’s comments leads to appeal of child rape conviction

Joseph Hall, of Snohomish, was sentenced to more than 13 years in prison. Now he faces another trial.

Jeffrey Vaughan
In unexpected move, Vaughan resigns from Marysville council

He got re-elected in November. But he and his wife moved to Texas when she received a job promotion.

Snohomish County Prosecutor Adam Cornell at the Snohomish County Courthouse on Monday, Nov. 15, 2021 in Everett, Wa. (Olivia Vanni / The Herald)
How to answer Snohomish County’s basic crime questions? ‘Transparent data’

An initiative funded in part by Microsoft could reveal racial disparities, while creating an “apples to apples” database.

Chris Rutland and son Julian buy fireworks from the Big House of Boom stall at Boom City on Thursday, June 30, 2022 in Tulalip, Washington. (Olivia Vanni / The Herald)
At Tulalip’s Boom City, fireworks are a family tradition

Generations have grown up at the Fourth of July institution. “Some people make good money, some are just out here for the pastime.”

Most Read