Scientists say we are due for a Cascadia Subduction Zone earthquake

Photo Credit: ISABEL GAUTSCHI - Structural Engineer David Bugni gives Eagle Creek Elementary students some pointers on structural soundness. Bugni had demonstrated the affects of earthquakes on buildings as part of the school's after school Science Technology Engineering Arts and Mathematics (STEAM) program.Lately, a lot of fuss has been made over earthquakes.

But this is Oregon, a state that has not been traditionally considered earthquake territory.

Most Oregonians residing in the Willamette Valley will have to search their memories before they remember the last Oregon earthquake they noticed in any significant way.

That would be the Scotts Mills earthquake, 20 years ago.

So chances are, the average Oregonian doesn’t spend a lot of time thinking about earthquakes.

However, experts are saying that there is a very good reason why you should be.

According to a recent press release issued by the Oregon Office of Emergency Management, Oregon is at risk for a magnitude 9 or higher earthquake within the next 50 years.

Magnitude 9... that’s about 27,000 times the amount of energy released during the Scotts Mills earthquake and about 900 times the amount of energy released during the 2010 earthquake that toppled Port-au-Prince and devastated Haiti.

Structural Engineer David Bugni explained that there is a great body of evidence from the last 10,000 years showing that major subduction zone earthquakes occur in Oregon every 300-500 years.

It has been 313 years since the last great Oregon quake.

“We’re due,” said Bugni.

Scientists predict that the next great earthquake to hit Oregon will occur along the Cascadia Subduction Zone (CSZ), a 600 mile fault line off the Oregon coast that runs from northern California to Vancouver Island.

Bugni pressed the open page end of two paper back books together to give a rough illustration of the tension between the Juan de Fuca and North American plates in the Cascadia Subduction Zone.

The books bent and buckled, but eventually, the pressure became too much and the books were forced to reposition.

Imagine a lot of water on top, and you’re probably picturing a pretty big wave.

Bugni said that a high magnitude CSZ earthquake would probably result in a tsunami that would have devastating impact on Oregon’s coastal cities.

The farther away from the epicenter of the quake, the less severe the impact. But in the event of a high magnitude CSZ quake, cities in the Willamette Valley would experience strong shaking that could last up to five minutes.

Five minutes may not seem like a long time, but it could result in landslides, structural collapse and the disruption of infrastructure, utilities and important services.

Further, Bugni said that it is unlikely that scientists would have much warning of such an earthquake. Maybe minutes of warning, if they were lucky.

If that wasn’t enough to get your attention, Bugni asks Oregonians to consider this:

“Up until 1993, Oregon wasn’t considered to be earthquake country,” he said. “Buildings weren’t required to have rigorous earthquake standards.”

Many Oregon buildings were built prior to 1993.

Bugni was part of a team of experts who worked to put together the Oregon Resilience Plan.

In April 2011, the Oregon House of Representatives tasked the Oregon Seismic Safety Policy Advisory Commission to put together a plan with policy recommendations to protect lives and commerce in the event of a large scale CSZ earthquake and tsunami.

The Oregon Resilience Plan was the result of that effort.

It was presented to the Oregon Legislative Assembly in February 2013. It is available online at

Bugni summarized some of his findings as a part of the study.

Many Oregon schools, institutional buildings, roads and bridges were build with sub-standard earthquake resilience precautions.

For example, Bugni explained, in the event of a high-magnitude earthquake it is likely that Interstate 5 would be too damaged to use for an emergency corridor due to the probability of landslides and bridge failures.

“This is serious,” Bugni said.

Emergency responders would have to rely on Highway 97 instead.

What now?

Alright, so Oregon is due for a major earthquake.

Things like roads, bridges, hospitals and institutional buildings throughout the state could be in trouble.

“Now the biggest thing we have to (avoid) is the inertia of doing nothing,” Bugni said. “It’s going to be a public policy and voters’ decision how much they want to do here.”

Large scale seismic upgrades won’t be cheap.

Estacada, Sandy and Gresham

When asked about specific communities, Bugni indicated that Estacada was in relatively good shape.

In 2000, the Estacada school district passed a large school bond that allowed for seismic upgrades to be made to schools and a non-seismically sound elementary school building was torn town and replaced with the Clackamas River Elementary building.

“The schools are in good shape,” Bugni said.

Bugni added that as the River Mill, Eagle Creek and Estacada High School buildings are all single-floor, wood buildings, they are likely to weather a high-magnitude CSZ earthquake with little damage.

“Wood is strong for its weight and would probably fair well,” Bugni said.

However, Bugni noted that the Ranger Stadium would likely suffer damage.

As to the dams on the Clackamas River, Bugni said they “should be fine.”

During the making of the Oregon Resilience Plan, Bugni was on the “critical buildings task-group” which evaluated the earthquake preparedness of emergency operations buildings such as police and fire stations throughout Oregon.

The Estacada Fire Department building was given a low rating.

Bugni’s team determined that it would be likely rendered inoperable for 60 days following a high magnitude CSZ earthquake.

Since firefighters serve frequently as first responders in emergency situations in Estacada, this would be a huge problem. Especially if the engines were trapped within the building.

However, Bugni noted that many other fire departments in the region were given a similar rating.

“Estacada isn’t any worse than the rest of the (Willamette) Valley,” Bugni said.

Bugni added that he evaluated Estacada City Hall in 2007 and recommended seismic upgrades.

In general, Bugni said that as most buildings in Estacada and Sandy are smaller, wood buildings, he’d expect them to weather an earthquake fairly well.However, he recommended that homeowners whose buildings were built before the mid-1970s, have a contractor check to see if the home should be bolted to the foundation.

Earthquake policy

Internationally, millions of people participated in earthquake drills on Great ShakeOut Day on Thursday, Oct. 17.

Oregon Governor John Kitzhaber declared October “Great ShakeOut Month” on Oct. 17.

Like many other Oregon communities, the city of Estacada participated in ShakeOut Day Oct. 17.

City leaders discussed plans for responses for emergency scenarios.

Melanie Wagner, assistant to Estacada’s city manager, explained that each fall, city leaders get together to participate in “emergency exercises.”

This was the first year the exercises were coordinated with ShakeOut Day.

Wagner said that the Estacada Fire Department and Sandy and Estacada Police Chief Kim Yamashita, along with Estacada officers, participated in the exercises.

Wagner added that the city of Estacada has received a grant from the state of Oregon to update their emergency operations plan.

The updates will include appendices that indicate responses to specific emergencies such as floods, wild fires and earthquakes.

Sandy City Manager Seth Atkinson explained that the city’s leaders usually hold a “emergency table top exercise” this time of year but haven’t yet done so due to personnel changes.

However, Atkinson said that the city is not unprepared.

“We have an emergency operations plan for hazards,” Atkinson said.

He explained that the plan covers “everything, including earthquakes.”

Gresham Emergency Manager Todd Felix had not returned requests for information about Gresham’s plans in the event of a high-magnitude earthquake by press time.

To learn more

For more information about Oregon’s earthquake risk, check out the Oregon Department of Geology and Mineral Industries’ website at

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