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Forget the San Andreas Fault — Meet its much bigger cousin

Mother Earth doesn’t give up her secrets all at once, but with continuous investigation, scientists are learning something new about our planet every day.

After years of investigation, scientists have learned much more about a fault line deep in the Earth’s belly, and it is huge, or as CNN is calling it, “a whopper.” It is called the Cascadia subduction zone (CSZ), and it runs 700 miles from Northern Vancouver Island, British Columbia to Northern California.

Between two of the Earth’s plates
The long, sloping subduction zone fault separates the Juan de Fuca and North America plates. This is what’s happening: The Juan de Fuca plate, one of the Earth’s smallest tectonic plates, is subducting, or being pushed below the northerly portion of the western side of the North American plate. The place where the two plates meet is called the Cascadia subduction zone.

Cascadia earthquake sources.

Cascadia earthquake sources.
US Geological Survey


The Juan de Fuca has been pushing against the North American plate for over 300 years, and eventually, the Juan de Fuca will be pushed underneath the North American plate, causing the region to sink about six feet, according to the Daily Mail.

Should the CSZ rupture in its entirety, it would cause a quake many times stronger than what the San Andreas fault is capable of producing, causing a huge tsunami and creating the worst natural disaster in the history of North America.

The Great Earthquake of 1700
“Cascadia can make an earthquake almost 30 times more energetic than the San Andreas to start with,” Chris Goldfinger, a professor of geophysics at Oregon State University told CNN. “Then it generates a tsunami at the same time, which the side-by-side motion of the San Andreas can’t do.”

And surprisingly, it has happened before. On January 26, 1700, the Cascadia unleashed one of the world’s largest earthquakes, causing a tsunami that traveled clear across the Pacific Ocean, destroying villages in Japan.

Scientists claim the Cascadia could generate a magnitude 9.0 quake, and the shaking would last from three to six minutes. “In this case, three minutes – and I’ve been in a 9.0 in Japan – three minutes is an eternity,” said Goldfinger. “It is a very, very long time.” Now, it’s just a question of when Cascadia unleashes the next “big one.”

Ghost Forests attest to CSZ’s lethality
Up until the 1980s, the Cascadia subduction zone was overlooked because it didn’t seem to move, or so we thought. “The more we learn about it, the less we like it because it is turning out to be a big hazard as well,” Goldfinger says. And to prove the CSZ has ruptured before, scientists were able to piece together the evidence by closely investigating “ghost forests.”

A three hundred year old remnant forest occasionally emerges from the sand and surf on the Oregon Co...

A three hundred year old remnant forest occasionally emerges from the sand and surf on the Oregon Coast. Nearby residents of Neskowin call it the “Ghost Forest”.
Michael Durham


Brian Atwater is a geologist with the U.S. Geological Survey. He began slogging through the marshes and along riverbanks in the Pacific Northwest in 1986, digging up and studying the residue where land meets the sea. Under the plants, trees and dirt and mud, he found a record of the changes in the landscape that gave him proof of one of the world’s largest earthquakes.

On a bank near Copalis Beach, Washington is a layer of sand on what was once a forest floor. “The field evidence for the tsunami here is the sheet of the sand that rests on the floor of the forest that these trees are rooted in,” said Atwater.

Exploring the evidence of past Subduction Zone Earthquake caused Tsunamis on the Pacific Coast. This...

Exploring the evidence of past Subduction Zone Earthquake caused Tsunamis on the Pacific Coast. This was a public walking tour on April 14, 2012 at the river bank of the Naiwaikum River led by Brian Atwater a USGS geologist.
Mike Challis


Atwater discovered that after the 1700 earthquake, the land dropped five feet, and the tsunami that hit several minutes later flooded a spruce forest bathing it in saltwater. The trees weren’t able to survive in saltwater, but there are the remains of many of those trees still left, dead trunks, the remains of the devastation caused by the quake.

Japanese earthquake researcher Kenji Satake, using Atwater’s notes, turned to diaries and logs kept by prominent families during the Shogun era, looking for information about earthquakes and tsunamis. From numerous records, he found evidence of an “orphan tsunami” 16-feet in height that struck the coast of Japan in January 1700. When there is no evidence of an shaking or a storm, the Japanese call the wave that hits an “orphan tsunami.”

You can’t see the Cascadia subduction zone as you can see the San Andreas fault, but it’s there, deep underwater. As Goldfinger says, there is no way of knowing when Cascadia will move. “I wish there were, but, no, there isn’t,” Goldfinger says. “We can’t look forward and say we are due or overdue really.”

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We are deeply saddened to announce the passing of our dear friend Karen Graham, who served as Editor-at-Large at Digital Journal. She was 78 years old. Karen's view of what is happening in our world was colored by her love of history and how the past influences events taking place today. Her belief in humankind's part in the care of the planet and our environment has led her to focus on the need for action in dealing with climate change. It was said by Geoffrey C. Ward, "Journalism is merely history's first draft." Everyone who writes about what is happening today is indeed, writing a small part of our history.

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