I'm really not setting out to commemorate one or two every day, but I'm reminded by Bu Element that today is the 310th anniversary of the last great Cascadia earthquake. (Actually, I misremembered; the last geo-versary I posted was Sunday, not yesterday) The quake is estimated to have been of a magnitude in the 8.7 to 9.2 range. There were no settlers in the area, so there is no written history of the event. How do we know its date? An earthquake of this magnitude would certainly create a tsunami, and the Japanese have obsessively accumulated the most thorough and lengthiest tsunami records on the planet. Red cedar trees killed by sudden subsidence into tidal salt water can give us the year through their rings. Older rings can be correlated to other trees that survived, and the year of the last ring in the killed trees would be the last growing season before the quake. Searching Japan's records, Brian Atwater found that a so-called "orphan tsunami," that is, a tsunami not associated with any known quake, hit Japan some hours after the quake occurred. Given records of tsunami travel speeds across the Pacific, it is estimated that the quake struck at 9:00 PM on the evening of January 26, 1700.
The PNW is not really prepared for such an event, but the level of awareness of the danger has grown dramatically over the last 20 years. Awareness is not the same as preparedness, but it's a necessary first step to get to that goal. Last year, one of the older and more dangerous buildings on the OSU campus was completely gutted and rebuilt. The original walls still stand, but they've been retrofitted and strengthened. The internal structure is completely new. This is a good thing. New buildings that have gone up in recent years have been required to meet higher seismic standards. I'm not sure (nor qualified to judge) whether those standards are sufficient, but this, too, is a good thing. Likewise, a number of schools around Corvallis have been replaced, shortening their lives, and moved to higher priority for replacement, on the basis of seismic concerns.
But there's a long way to go. "The Big One," as every locale calls their potential great quake, if they anticipate one, is expected to be in the 9+ range.
So given our state of semi-preparedness, what should you do? Well, think about it, for one thing. It's a rare day that "what would I do if it hit right now?" doesn't flit through my mind for a second or two. I consider my apartment as a structure relatively safe, and I keep heavy things low. I keep several gallons of water stashed, and cycle through them so they stay fresh. (I'm not so good about food, but I can go a long time without food- I think my record is 9 or 10 days. After the first day, I just don't feel hungry.) At my coffee shop, it's a one story concrete building, I suspect (but don't know for certain) over re-bar. If the quake hit while I was here, I would more or less stay put until the shaking stopped, then get out as quickly as was safe. The big plate glass windows scare the hell out of me, so if I was indoors near one, I'd try to get a few feet (at least) away from them. If I was outside, I'd get away from any walls. Often the first instinct is to rush out of a building, but records show that facades and roofing material often fall off during the shaking; that the worst time to try to leave. Likewise, if you're near the exterior of a building, try to get away from the walls. That does not mean "run higgledy-piggledy out into traffic." Drivers weren't expecting the quake either, and neither are they expecting you to run out in front of them as the earth wallops up and down like a bronco.
In short, I expect that I'll feel panicky, if it hits while I'm here in western Oregon. But I'm fairly confident that I'll react sensibly, simply because I've thought about it and mentally rehearsed it many, many times. That is no guarantee that I'd get through it unscathed or even alive. But it raises my chances.
What would you do if a giant quake hit where you are right now? No place is "immune."
Think about it.
Followup: Heh. I thought I posted a bit on this last year too. I did. Almost to the minute.
Is This Your Hat?
2 years ago