Portland State Geology Professor Scott Burns has some serious credentials, like being former Vice President of the IAEG (International Association of Engineering Geologists). But I like him because he takes complicated subjects and puts them in plain English.
In part one of this interview, I asked Professor Burns about the Cascadia Subduction Zone and if the Northwest is next for a major quake and Tsunami.
This time, it’s about quake impacts for the Willamette Valley and Southwest Washington.
- Would a Subduction Zone quake of magnitude 8.0 to 9.0 ‘plus’ off the coast have a serious impact for I-5 Corridor cities like Salem, Portland & Vancouver?
A subduction quake will have a huge effect on the valley. We will have extensive shaking. We are trying to keep the I-5 open and that is why we are trying to shore up all bridges on I-5. The major roadwork north of the Terwilliger Curves on I-5 is aimed at retrofitting for earthquakes the bridge below those slopes. Drivers never realize they are going over a bridge there. All structures in the valley will be affected.
- Lots of people still talk about the “spring break quake” that shook the Willamette Valley. But that was a long time ago. Are we overdue for something like that again – and how big could a possible valley quake actually be?
We can never really know when the next crustal quake is going to happen. We need to be prepared. We have a long way to go to know about each one of the faults of the area (California has invested a lot of money into their Alquist Priolo system so each fault has a name, date of last movement, maximum size one can expect from it, and what is the recurrence interval in between each quake). We have nothing like that here in Oregon because we have never invested in earthquake research the way California has.We are overdue for a large one in the North American crust, but when will it happen? We do know that a local quake will not be over 6.5 magnitude based on the lengths of the faults (i.e. the longer the fault the larger the possible quake).When it comes to earthquakes, what makes you lose sleep at night, or have we already covered it?
I am bothered that some people are not prepared in their homes. I would not want to live in a house on stilts in the subduction quake – very dangerous. I am worried about being away from my family when it happens.
- I’ve always carried earthquake insurance on my house even though it’s expensive. As a geologist who knows the risk around here, do you have it, too?
I have earthquake insurance on my home. It is important. It was a high deductible, but it covers your house being knocked off its foundation (in which case it is toast!). My biggest investment is my home and I want to have it covered during a big quake. If you amortize the amount of the insurance out for 30 years, it is not expensive. Remember, most of our homes (anything built before 1988) were built with no earthquake building codes – most homes are not built for earthquake country and need earthquake insurance.Thanks, Professor Burns, for all your help over the years. I really appreciate it!