Cascadia subduction zone article in The New Yorker
 

A friend sent this article to me. Living in the east, we most often hear and read about "earthquakes and California". I was not aware the Cascadia Subduction Zone nor the potential magnitude of an earthquake in the region. The potential devastation described in the article is beyond comprehension.

http://www.newyorker.com/magazine/20...really-big-one

Lot of faults and zones in the US nobody much talks about. I learned about New Madrid when I lived in Memphis. Geologists say it lets go very infrequently but when it does, its big.

I saw a journal kept by a riverboat captain where he described the last New Madrid quake. For a brief time, there was a waterfall on the Mississippi and the river ran north for a short time. The damage from one like that today would be pretty devastating.

I worry about the Cascadia subduction zone because I live right near it. I just hope that whenever that earthquake comes that it's a long time away in the distance and that it really is not as bad as everyone predicts.

I have been through several earthquakes here, and I happened to be San Francisco at a trade show when the 1989 earthquake occurred. I believe this is the Loma Prieta, California earthquake, which killed sixty-three people and caused six billion dollars’ worth of damage.

I do not look forward to any more earthquakes. Fortunately, I live out in the country, away from the big city, so hopefully the damage we experience out here will not be as bad. The big worry are the kids in the schools. My wife was in her 2nd grade classroom when the 2001 Nisqually earthquake occurred. That is the one that cracked the dome on the Capitol Building in Olympia -- pretty scary. However, the schools around here held together well during that quake.

- Glenn

Ya never know what this great big ol' ball we live on will start bouncing!

Glenn....I was at the Bay Bridge when that SF quake hit.....what a ride!

That is a great article! Fascinating science. Unsettling revelations. Important and interesting reading, even for folks who have no ties or connection to the Pacific Northwest.

Thanks for sharing.

My next door neighbor in a rural area of Humboldt County is a world class (i.e., they fly her around the world after earthquakes to investigate) earthquake specialist. There are several living in that area. One of her colleagues taught an environmental geography class I took up there, studying earth movements.

At College of the Redwoods, just south of Eureka, CA, he took us outside the classroom one day, pointed down the hill the school rests on, out across Highway 101 to a cow field leading off to Humboldt Bay. He pointed out the offset of the old fence lines.

One branch off the Cascadia connections, he said, comes in from the Pacific, across that field and runs East up under the college... our class room building, actually.

He said that when (not if, but when), the Cascadia subduction zone cuts loose, everyone in the classroom will go through the ceiling... We had many interesting field trips in that class around Humboldt County. It was both fascinating and frightening to know so many people, experts, in that field of geology and listen to what they had to say about the Big One (and they were always talking about the Cascadia event, not San Andreas!).

Occasionally something "new" hits the popular news and it's a big deal again for those who haven't been aware of it for decades.

I was in Humboldt for the 7.2 quakes in 1980 and 1992. It was fascinating to go out to the Lost Coast, South of Eureka and see the seabed along a long stretch of the coast newly exposed after rising about 4 feet during one of those quakes.

It will be catastrophic when it happens.

Glenn, I'm under the impression (probably mistaken) that a big concern for coastal residents in the PNW is not so much damage or injury from an earthquake itself, but from a possible resulting tsunami. Is that not so?

I've been in the Bay Area almost 30 years, through the Loma Prieta, and Napa Valley Quakes, and a few random smaller ones. Having a gallery with lots of gems, minerals, and crystals on display, and many glass shelves, that's located right on Richardson Bay, the possibility of a big, destructive earthquake does cross my mind from time to time.

But there are other possible natural disasters, that can result in catastrophic damage and loss of life. Floods, hurricanes, and tornados can all wreak havoc, and occur far more often than earthquakes and tidal waves. There are also other parts of the US that have had major earthquakes in the past, and a strong possibility of future big ones, too.

You are exactly right. For us out near the coast, a huge concern is a tsunami. So I should be more careful about how being out in the country might be less of a problem than being in a big city.

My home is well up one of the river valleys and on high ground, so I think it's unlikely that where I live will be affected by a tsunami. But down in Aberdeen, south of me by about 7 miles, they are right along the Chehalis River and Grays Harbor at essentially sea level. Those little towns near the water will be flooded for sure.

All the school kids (my grand children) drill for a tsunami -- where to go, where is the highest ground in the city, all that. I keep hoping it will be like our drills in the school hallways for a nuclear war when I was a kid. I just pretended it would never happen. I'm sure I am doing the same thing now.

So you are not mistaken at all.

- Glenn

My friends and professors in the seismology field up there are both matter of fact about what WILL happen as well as fatalistic. There's not much you can do about it other than to take the drills seriously, while science continues investigating early warning clues.

City planners could do more about where and to what degree they allow building, but much of that is a matter of a horse that's already left the gate.

I have a large plastic container with our camping gear in it which doubles as earthquake emergency kit. I have an ax and pry bar in my closet in case of being stuck in the house or trying to into the attached garage to get to the earthquake kit. I have the same stuff in the trunk of my car.

But you can only do so much for what WILL happen. Part of it is a matter of it happening in our generation's lifetime or our kids or grandkids... All of which is an eyeblink in geological times, although it appears that some major faults are well overdue for stress relief.

That was the article to which I referred in my Cajon Pass brushfire thread. I lived in Seattle (U. Dist. a block uphill from the Ship Canal) for 7 years and experienced a few “nuisance-level” quakes (plus a slightly bigger one when I went back for a visit 20 years later), but ironically the biggest quake I felt was one in NYC in Jan. 1994 (centered near Albany, felt only in the Bronx and on anything floating in the surrounding rivers--including the floating dining room section of Brooklyn's River Cafe, which was slammed against its moorings).

True, here we can get tornadoes (had a couple touch down today in the far NW ‘burbs and southern WI), but we get at least a few minutes' warning, and all public buildings have designated tornado shelter areas. (We do spend an anxious hour or so in our basement once every couple of summers). We also get plenty of advance notice of floods (including flash), and we all know the mantra “turn around, don’t drown.”

Having lived in the Jackson Hole are for 30 yrs. there were two quakes that we experienced but both minor. The main concern there is two fold one the possibility of a massive quake 9.0 or bigger, because of expansion in massive mantel plume in the Yellowstone Caldera. And the other is, if that caldera were to erupt and produce the "Super Volcano" ??? other than those two little concerns the area is staggeringly beautiful and serene

Yes, two little concerns that would result in massive destruction. :)

I'm asking mainly out of curiosity, I have no background knowledge at all, but would the Mt St Helens eruption figure in nhere at all? I'm thinking maybe it acted like a huge pressure relief valve? I understand I'm probably wrong, but just thinking out loud.

VEI – 8 eruptions are colossal events that throw out at least 1,000 km3 (240 cu mi) Dense Rock Equivalent (DRE) of ejecta.

VEI – 7 events eject at least 100 cubic kilometres (24 cu mi) DRE.

VEI – 7 or 8 eruptions are so powerful that they often form circular calderas rather than cones because the downward withdrawal of magma causes the overlying mass to collapse and fill the void magma chamber beneath.

By way of comparison, the 1980 Mount St. Helens eruption was a VEI-5 with 1.2 km3 of ejecta.

There was a 5.1 quake right before the eruption. That's not much as earthquakes go.