HomeLatest ThreadsGreatest ThreadsForums & GroupsMy SubscriptionsMy Posts
DU Home » Latest Threads » Forums & Groups » Main » General Discussion (Forum) » Must Read: From 2015 The ...

Mon Jul 8, 2019, 04:33 PM

Must Read: From 2015 The Really Big One

https://www.newyorker.com/magazine/2015/07/20/the-really-big-one
<snip>
Most people in the United States know just one fault line by name: the San Andreas, which runs nearly the length of California and is perpetually rumored to be on the verge of unleashing “the big one.” That rumor is misleading, no matter what the San Andreas ever does. Every fault line has an upper limit to its potency, determined by its length and width, and by how far it can slip. For the San Andreas, one of the most extensively studied and best understood fault lines in the world, that upper limit is roughly an 8.2—a powerful earthquake, but, because the Richter scale is logarithmic, only six per cent as strong as the 2011 event in Japan.

Just north of the San Andreas, however, lies another fault line. Known as the Cascadia subduction zone, it runs for seven hundred miles off the coast of the Pacific Northwest, beginning near Cape Mendocino, California, continuing along Oregon and Washington, and terminating around Vancouver Island, Canada. The “Cascadia” part of its name comes from the Cascade Range, a chain of volcanic mountains that follow the same course a hundred or so miles inland. The “subduction zone” part refers to a region of the planet where one tectonic plate is sliding underneath (subducting) another. Tectonic plates are those slabs of mantle and crust that, in their epochs-long drift, rearrange the earth’s continents and oceans. Most of the time, their movement is slow, harmless, and all but undetectable. Occasionally, at the borders where they meet, it is not.

Take your hands and hold them palms down, middle fingertips touching. Your right hand represents the North American tectonic plate, which bears on its back, among other things, our entire continent, from One World Trade Center to the Space Needle, in Seattle. Your left hand represents an oceanic plate called Juan de Fuca, ninety thousand square miles in size. The place where they meet is the Cascadia subduction zone. Now slide your left hand under your right one. That is what the Juan de Fuca plate is doing: slipping steadily beneath North America. When you try it, your right hand will slide up your left arm, as if you were pushing up your sleeve. That is what North America is not doing. It is stuck, wedged tight against the surface of the other plate.

Without moving your hands, curl your right knuckles up, so that they point toward the ceiling. 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.) But it cannot do so indefinitely. There is a backstop—the craton, that ancient unbudgeable mass at the center of the continent—and, sooner or later, North America will rebound like a spring. If, on that occasion, only the southern part of the Cascadia subduction zone gives way—your first two fingers, say—the magnitude of the resulting quake will be somewhere between 8.0 and 8.6. That’s the big one. If the entire zone gives way at once, an event that seismologists call a full-margin rupture, the magnitude will be somewhere between 8.7 and 9.2. That’s the very big one.

In the Pacific Northwest, the area of impact will cover* some hundred and forty thousand square miles, including Seattle, Tacoma, Portland, Eugene, Salem (the capital city of Oregon), Olympia (the capital of Washington), and some seven million people. When the next full-margin rupture happens, that region will suffer the worst natural disaster in the history of North America. Roughly three thousand people died in San Francisco’s 1906 earthquake. Almost two thousand died in Hurricane Katrina. Almost three hundred died in Hurricane Sandy. fema projects that nearly thirteen thousand people will die in the Cascadia earthquake and tsunami. Another twenty-seven thousand will be injured, and the agency expects that it will need to provide shelter for a million displaced people, and food and water for another two and a half million. “This is one time that I’m hoping all the science is wrong, and it won’t happen for another thousand years,” Murphy says.

13 replies, 707 views

Reply to this thread

Back to top Alert abuse

Always highlight: 10 newest replies | Replies posted after I mark a forum
Replies to this discussion thread

Response to malaise (Original post)

Mon Jul 8, 2019, 04:42 PM

1. K&R

and bookmarking. I am only able to skim this right now. Will come back to read more closely and when I'm able to use both hands as instructed for better understanding.

Thanks for posting!

Reply to this post

Back to top Alert abuse Link here Permalink


Response to malaise (Original post)

Mon Jul 8, 2019, 04:48 PM

2. The small city along the Oregon Coast where l live has an entire

department devoted to disaster preparedness, and continues to spend considerably funds to educate people on what to do. A monster tsunami is the real danger. Most of it is basic common sense, but a certain amount of specialized equipment and supplies are required if one takes the threat seriously. Still worth living here among such natural beauty more than worth it.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Enoki33 (Reply #2)

Mon Jul 8, 2019, 04:51 PM

4. We've been waiting for our big one

The last big quake here was in 1907. My view is that we should be aware, be as prepared as we can and enjoy our lives.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Enoki33 (Reply #2)

Mon Jul 8, 2019, 10:27 PM

12. I've read a couple of stories about the most realistic SHTF scenarios


of a big one there. There's really no place to go when the tsunami hits, and that is assuming people could even physically get away from the coast damage and I-5 was even intact.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to malaise (Original post)

Mon Jul 8, 2019, 04:51 PM

3. I was on a committee a couple years ago looking at impacts and responses to the CSZ

I scared the bejeezus out of me. Ended up stock piling some emergency supplies. I was on the committee looking at the electrical grid but heard about lots of other stuff. Electricity will be down up and down the coast, roads and bridges out. It’ll be hard to physically escape because of that, really if you can make it to the other side of the mountains you’ll be relatively ok. But one thing I hadn’t thought about is there’ll be no gasoline. Any supplies that make it thru will go to first responders. And it’ll take many months/years for recovery. Think of Katrina and multiply by thousands.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to captain queeg (Reply #3)

Mon Jul 8, 2019, 04:54 PM

5. Living on a hurricane island has taught me to always have a full tank of gas

I learned that after Gilbert in 1988. It annoys the hell out of everyone around me but my tank is always full. As soon I use a quarter of my gas I top up. It has worked out well because it never costs that much.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to malaise (Reply #5)

Mon Jul 8, 2019, 05:12 PM

7. Yes, that was the single strongest suggestion for average folks

Thanks for reminding me, I’ve let that slip over time. A full tank of gas would probably get you to safety sooner or later. And all those portable gas generators are going to be useless w/o gasoline.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to captain queeg (Reply #7)

Mon Jul 8, 2019, 05:34 PM

8. Yep and if the car is full you can always steal some for the generator

I keep reminding people that our grandparents used to store eggs in rock salt and they'd stay fresh for weeks.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to malaise (Reply #5)

Mon Jul 8, 2019, 10:50 PM

13. You and me both..it came in handy during one hurricane



Doesn't hurt to have that extra gas for a variety of reasons.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to malaise (Original post)

Mon Jul 8, 2019, 04:58 PM

6. K&R. nt

Reply to this post

Back to top Alert abuse Link here Permalink


Response to malaise (Original post)

Mon Jul 8, 2019, 06:12 PM

9. I watched this video a few days ago

It's a little over an hour long, but really interesting (if you like that sort of thing, which I do). It's about the Juan de Fuca plate colliding with the North American plate: how they are colliding (Juan de Fuca is subducting under North America), what kinds of earthquakes are caused, how everything west of I-5 would be "toast," etc.


&list=PLwNJg2mCrcQRYmYJzHUv7YxO40JlNbAWe&index=7


Yikes! Between Yellowstone's supervolcano and the continental plate shoving match in Cascadia, I don't think I will ever go north of 37 degrees north again!

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Leith (Reply #9)

Mon Jul 8, 2019, 06:15 PM

10. Bookmarked for later tonight

Thanks Leith

Reply to this post

Back to top Alert abuse Link here Permalink


Response to malaise (Original post)

Mon Jul 8, 2019, 07:50 PM

11. I'm kind of amazed that the death toll is only expected to be 13,000.

Not that I would want it to be more and would hope for it to be less, but if this were to happen the way they it could happen, it seems like it would be much more destructive and deadly than that.

However, I am sure being well prepared for such an event will do a lot to minimize the casualties and damage.

Reply to this post

Back to top Alert abuse Link here Permalink

Reply to this thread