New research shows chance of ‘Big One’ in NW higher than believed

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CORVALLIS, Ore. - Oregon State University researchers say earthquakes off the coast of Oregon and Washington are happening more often than they ever thought before, and new findings show the chance of a big quake hitting the coast in the next 50 years is even higher than previously thought.

Oregon State University marine geologist Chris Goldfinger works in a facility the researcher refers to as an "earth library."

It is an unassuming building that's kept below 40 degrees at all times and holds rows upon rows of white tubes containing core samples of the earth, full of deep sea sedimentation collected from all over the world.

"We can go a lot of places in the world in here and see hundreds of thousands of years of earth history," Goldfinger told KPTV. "These things are like library books, they're good forever."

Goldfinger said any shift in the sea floor is recorded naturally in the submarine landslide deposits, much like sound is picked up on a tape recorder.

"If you can learn how to read the tape and understand what's going on, you get this incredible record of time," he explained.

The samples may just look like a lot of old mud to most people, but for Goldfinger and his students, the mud is a timeline of the earth's movements. Earthquakes, he said, that can be traced back thousands of years.

To better understand when the next big one could hit the coast of Oregon and Washington, Goldfinger and his OSU colleagues, alongside researchers from British Columbia and Spain, recently went out to sea to pull core samples from the Cascadia Subduction Zone.

The group gathered measurements from 195 core samplings. Before then, they only had about a dozen samples to work with.

"For us, it was a long process to go to sea, and to do the work and to collect the cores and process and analyze them," Goldfinger said. "It's, it's like building a car in a factory. It doesn't look much like a car at first and then toward the end once you get the paint on, it looks finished."

Goldfinger said their finished research shows the frequency of earthquakes appear to be happening more often than they first thought, noting that is because the spatial boundaries of those earthquakes turned out to be far bigger.

"Some earthquakes that we thought were limited to Oregon extended to Washington, so that increased the number they experienced, and the same thing happened to northern Oregon," he explained. "Some earthquakes that we thought were limited to south actually extend further north."

Goldfinger added that this also means that the chance for the Cascadia Subduction Zone to produce a 9.0 earthquake in next 50 years is higher than previously expected, too.

"For Washington, we thought the recurrence time for an earthquake was 500 years, and it's already been 315, but that number has now dropped to 430 years," he said. "For northern Oregon, we thought the repeat time of an earthquake occurring was a bit over 400 years, and that dropped to 340 years."

That is a terrifying thought, especially knowing that four major cities, including Portland, were built on top of the subduction zone - cities that were all built before earthquake standards.

"In the US, we're not used to thinking that we're like a third world country," Goldfinger said. "In this instance, where cities are built on a fault and can do nothing about it, we're essentially in the same position as Indonesia."

Goldfinger hopes his research gives people a chance to prepare, though he knows the likelihood of retrofitting an entire city is a staggering concept.

"It's hard to imagine how that's going to happen and yet we really have to do that, the only other choice is to let it happen."

OSU researchers say there have been 43 major earthquakes in the past 10,000 years on the Cascadia Subduction Zone, sometimes on the entire zone at once and sometimes only on parts of it.

When the entire zone is involved, it's believed to be capable of producing a magnitude 9.1 earthquake.