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[Earth] Scary article about the Cascadia Subduction Zone


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Man...i've experienced only one earthquake in my life - at measly 3 Richters. And still it was unnerving experience. After reading this article...i am very, very glad to live in boring, old Central Europe.

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Ooh, fun, I'm sitting just a few miles outside the "I-5 corridor" mentioned in that article, and this is the first I've heard about it. If it waits 30 years to happen, it probably won't be my problem, but when that's the best you can say about something, ugh.

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I've heard about it various times before, and yeah, that whole region is more overdue for a big quake than the San Andreas fault is.

Theres also the possibility that it'll sort of unzip and trigger other quakes further down the US coast.

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Read this yesterday, a real eye-opener. It's definitely prioritized my plans for a supply kit for my family. If you're in the region it's worth your time to have two~three weeks worth of supplies ready to go at a moment's notice; one less thing to think about if you survive the disaster. Also made me reprioritize certain future improvements on the house I'm trying to buy.

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(X) previous event in modern history

(X) relevant recurrence (although we only got an average) and impact

(X) good research base

(X) modern analogues

(X) data

Be afraid, be very afraid.

It's hidden gems like these that people need to be afraid of, not overhyped 500,000-year cycle 'thupervolcanoeth' like Yellowstone.

Although looking at it from a more restrained view,

- the next event need not necessarily be the apocalyptic disaster described in the article, nor even a major one. However, the pattern of events at this fault appears to invalidate that idea (?)

- as an individual, you're likely to be off worse worrying about this for 80 years and then nothing happens until decades after your death, than maybe just asking for more earthquake protection and hoping for the best

Edited by Aanker
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I have lived in the Northwest most of my life. I have been hearing about the BIG ONE for about 20 years. I remember some news story they did on it a few years ago where it showed if the REALLY BIG ONE happened, Vancouver Island would rip apart. It was pretty scary.

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- the next event need not necessarily be the apocalyptic disaster described in the article, nor even a major one. However, the pattern of events at this fault appears to invalidate that idea (?)
I generally temper my concerns with the belief that many articles like this overhype the disaster potential, but it does seem pretty plausible, which is why I also believe it's okay to be reasonably prepared.
- as an individual, you're likely to be off worse worrying about this for 80 years and then nothing happens until decades after your death, than maybe just asking for more earthquake protection and hoping for the best
The public good is a laudable goal but, all too often in the U.S., no one wants to pay for it. It's generally a safer bet for the individual to be prepared than to expect public policy to change.
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(X) previous event in modern history

It's hidden gems like these that people need to be afraid of, not overhyped 500,000-year cycle 'thupervolcanoeth' like Yellowstone.

This is actually somewhat similar the Yellowstone - it's recurrent, would cause massive damage, and is overdue. Both are generally ignored. On the other hand, this particular fault has a much lower recurrence time, so an earthquake is much more likely to occur in the next several decades than Yellowstone erupting. We'd also have a few days or weeks of warning with Yellowstone, as opposed to the 0-90 seconds of warning that this earthquake would give people.

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This is actually somewhat similar the Yellowstone - it's recurrent, would cause massive damage, and is overdue. Both are generally ignored. On the other hand, this particular fault has a much lower recurrence time, so an earthquake is much more likely to occur in the next several decades than Yellowstone erupting. We'd also have a few days or weeks of warning with Yellowstone, as opposed to the 0-90 seconds of warning that this earthquake would give people.

The USGS has a very good summary of the (shall we say) myths about Yellowstone, see http://volcanoes.usgs.gov/volcanoes/yellowstone/faqs_misconceptions.html

I guess one way to look at it is that before the caldera itself formed, there was a lot of terrain above the magma to keep the pressure rising until the release was inevitably catastrophic in nature. However, once the eruption had taken place and all this material had been displaced, we were left with a large area covered in faults and fractures where subsequent magma could then erupt relatively peacefully in steam explosions or surface lava flows. Simply put, the formation of the caldera does not facilitate future massive eruptive events. Of course, steam explosions are dangerous in their own right, but mostly to the tourists within the bounds of the natl. park. That said, the Snake River Plain as a whole may experience a future 'supervolcanic' eruption, but the periodicity of these events appears to be in the range of millions of years as the plate moves only slowly.

I think Yellowstone is overhyped because it is more easy to imagine a large movie-like explosion in a crater which we obviously can observe. The Cascadia fault is much more obscure as a concept to the uninitiated, and there are very few clear 'fingerprints'... If you take a drive into Yellowstone through the mountains in the east, the first thing that really strikes you is how absolutely flat and spaceous the basin is: the 'next' mountain is all the way over in the distant horizon. That's the sort of stuff we can see and maybe understand.

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It's telling that FEMA put the best case scenario in their report, the one with the fewest people on the beaches. Quite frankly, even then I wouldn't expect them to be able to deal with the disaster in any effective way. Their official advice can be summed up as "Don't live there. If you do, be ready to run. Fast."

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It's telling that FEMA put the best case scenario in their report, the one with the fewest people on the beaches. Quite frankly, even then I wouldn't expect them to be able to deal with the disaster in any effective way. Their official advice can be summed up as "Don't live there. If you do, be ready to run. Fast."

How do you deal with an earthquake and tsunami in an effective way, I wonder? I don't think there's much FEMA *can* do.

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The sheer size of potential disaster makes any prevention a moot point. There is just too many people, buildings, roads etc. in danger zone. No one will build big enough system of sea walls, to protect half of the continent from tsunami. Even if a dedicated government would cough up the money, human inertia would get in the way immediately. There would be protests from landowners fearing such big scale project will decrease value of their property. Ecologists would protest against devastation of shore areas. Local politicians would squabble over money and contracts. And conspiracy nuts would accuse everyone, from government to scientists of malicious intents.

In such environment FEMA and similiar organisations can prepare only to perform damage control, search and rescue, relief and evacuation operations.

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Just look at how Chile handled the 2010 earthquake, which was quite similar to what could happen in the Northwest. It was a magnitude 8.8 earthquake (one of the strongest ever recorded) that hit about 80% of the country's population. Chile is a poorer country than the US, and the emergency response wasn't exactly a success, but still less than 1000 people lost their lives.

This can probably be attributed to three main causes:

  1. Earthquakes are common in Chile. I lived there for a couple of years, and experienced around 10 minor (magnitude 5-6) ones. This constantly reminds the people that the threat is real.
  2. Chile has a strict construction code that is usually enforced.
  3. There are clearly marked escape routes in regions that could be affected by tsunamis (or volcanic eruptions or a number of other natural hazards).

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The USGS has a very good summary of the (shall we say) myths about Yellowstone, see http://volcanoes.usgs.gov/volcanoes/yellowstone/faqs_misconceptions.html

I guess one way to look at it is that before the caldera itself formed, there was a lot of terrain above the magma to keep the pressure rising until the release was inevitably catastrophic in nature. However, once the eruption had taken place and all this material had been displaced, we were left with a large area covered in faults and fractures where subsequent magma could then erupt relatively peacefully in steam explosions or surface lava flows. Simply put, the formation of the caldera does not facilitate future massive eruptive events. Of course, steam explosions are dangerous in their own right, but mostly to the tourists within the bounds of the natl. park. That said, the Snake River Plain as a whole may experience a future 'supervolcanic' eruption, but the periodicity of these events appears to be in the range of millions of years as the plate moves only slowly.

I think Yellowstone is overhyped because it is more easy to imagine a large movie-like explosion in a crater which we obviously can observe. The Cascadia fault is much more obscure as a concept to the uninitiated, and there are very few clear 'fingerprints'... If you take a drive into Yellowstone through the mountains in the east, the first thing that really strikes you is how absolutely flat and spaceous the basin is: the 'next' mountain is all the way over in the distant horizon. That's the sort of stuff we can see and maybe understand.

Thanks. It's interesting that these things existed, and possibly exist today. But reliving to know that they may have expired and earth had "grown up" past the explosive supervolcano stage. :o

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interesting article bit theres something that bugs me :

Under pressure from Juan de Fuca, the stuck edge of North America is bulging upward and compressing eastward, at the rate of, respectively, three to four millimetres and thirty to forty millimetres a year. It can do so for quite some time, because, as continent stuff goes, it is young, made of rock that is still relatively elastic. (Rocks, like us, get stiffer as they age.

err... so the subducting plate, Juan de Fuca, is oceanic and the one on top (i don't know the precise vocab in english...), the North American plate, is continental right ?

But the continental crust is the oldest and is about 4.5 giga-years while any oceanic crust is no older than a few million years (around 200-400millions iirc). and that is totally in contradiction with the article...

So according to their "old rocks get stiffer", the oceanic crust should be ice cream-soft and the continental crust rock-hard (pun intended). wich is not true and brings another nonsense in the article...

can anyone enlighten me ? i might be wrong there but i'm pretty sure for the rock ages and the real "elasticity" of the oceanic crust

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Oceanic one is soft. That's why it's bending down and diving under the continental plate. But it still generates enough force on the continental plate as it does so to cause the later to bulge.

I know that, but that´s not what the article is saying ! It´s the "old=hard" that is misleading

EDIT also, K^2, the oceanic plate does not dive under the continental because it's softer, but because it's denser (2,7 for continental vs 2,9 for oceanic iirc). it actually gets denser as it ages... (But then again, it being soft (ductile) is necessary for it to dive, even though it is not the cause)

Edited by Hcube
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geography ?

Yes, today's landscape would be very bizarre. The oceanic plates would likely rise above the continental plates.

As for the East-Coasters like me, there's this thing, which isn't such an impending threat but is still food for thought. (Not the best website, yeah, I know. There's a lot of conspiracy about the actual event, but there is real evidence of the structural decay of the island.)

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Well, that's a pity. There's some cool places on the American West Coast.

Sounds like the best thing that can be done is experiment with cheaply retrofitting earthquake resistance into structures.

A pitty we can't manage tectonic pressures somehow.

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