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1700 Cascadia Earthquake

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Re: 1700 Cascadia Earthquake

#71
post #35
post #12

Earlier quoted context omitted.

Nearby this in Oregon is Crater Lake, which is the stunning remnant of a catastrophic volcanic eruption 7,700 years ago. The volcanic explosivity index classifies it as a 7, "super-colossal", i.e. an order of magnitude larger than Krakatoa. And indeed there are Native American tribes who have passed down the story of the eruption over the millennia, believing it to be the site of a battle between gods. Super cool to…

I'm pretty sure these intersections are often coincidence. There are enough myths across enough cultures that you're bound to find some with similarities to real events. For example: if the story of Sodom and Gomorrah had been a Klamath myth instead of a Hebrew myth, people would claim that it was from the eruption of Crater Lake. The same goes for pretty much any prehistoric flood.[1] 1. https://en.wikipedia.org/wik…

There really was a worldwide flood. It did not recede; all the water is still there. Instead, people had to abandon where they lived and move uphill.

It didn't happen all in one day, or year. But there were many places where the water moved inland by three feet per year; any beach one knew as a child was gone by adulthood.

Millions of square miles of what was lowland is now underwater -- the region between Indonesian islands; for hundreds of miles out to sea from Viet Nam all the way up to Korea; all the space between Australia and New Guinea; thousands of square miles off India; the whole Persian Gulf; England and Ireland were not islands; from Florida to Louisiana; from Argentina out to the Falklands.

These places were prime habitat (possibly excepting near the Falklands, and northern England), so not unpopulated.

It seems significant that the oldest known civilizations, in Mesopotamia and the Indus valley, arose immediately uphill from especially major inundations. Australian oral records have precise accounts of conflict resolutions over people moving uphill into land already occupied for 40,000+ years.

Re: 1700 Cascadia Earthquake

#73
post #41

Add onto this that many or most of the mountains in the area are active volcanoes that are overdue for an eruption, and the Seattle area could be in for a real bad time over the next 250 years. The projections of a moderate eruption of Mount Rainier (aka Tahoma/Tacoma) include flows reaching all the way to Renton/South Seattle.

“Most” of the mountains are not active volcanos. There are only 4 in Washington: Baker, Rainier, St Helens, Adams but hundreds of other mountains. Rainier is really the only one that poses serious danger to a populated area. Tacoma in particular will be destroyed by lahars alone in a large eruption

Re: 1700 Cascadia Earthquake

#74

"Our operating assumption is that everything west of Interstate 5 will be toast." Ouch.

I really doubt it. A lot of the land West of I-5 is drumlins/drumlinoids like Fremont Ridge in Seattle. That's solid ground that has been around since the last glaciation and has come through many earthquakes just fine.

On the other hand...If somebody like Brian Atwater said it, that would really get my attention. He's one of the main geologists who tracked down the geological evidence to date the 1700 Earthquake. The force is strong in that one. [1]

[1] https://en.wikipedia.org/wiki/Brian_Atwater

Re: 1700 Cascadia Earthquake

#75

I live in Portland and have a slide-in truck camper on my property. I use it for camping of course, but it is also part of my earthquake preparation plan. It is solar powered but also has a built-in propane generator. It is fully self-contained with all the comforts of home including fresh water storage, a galley with oven, stove, freezer and fridge. A bathroom plus a hot shower, comfortable bed, large pantry, closet…

This type of stuff is what always made the west coast unappealing. Where I live, disaster is a bad ice storm, blizzard or localized flooding. Complete devastation just isn’t my thing.

I wish it kept more people away.

Re: 1700 Cascadia Earthquake

#76

Here is an excellent lecture on the subject from CWU professor Nick Zenter. If you watch this there is a good chance you'll decide to watch all of his lecture on the channel. Very enthralling. https://youtu.be/UJ7Qc3bsxjI

Love Nick Zenter! He has a great podcast too! I’d love to see his talks in person one day.

Re: 1700 Cascadia Earthquake

#77
post #69
post #65

Earlier quoted context omitted.

California gets hit with earthquakes quite often, and so has been made more resilient. When a big one hits Seattle or the Midwest is when you’ll see untold damage. Just compare bridge pillars in various parts of the country.

When the "big one" hits the pacific NW, bridge design is not going to save significant areas from complete destruction. I am talking about the Cascadian Subduction Zone letting go which happens every 200 to 1200 years (41 times in the last 10000 years). The last time this happened, in 1700, there was a 9.0 earthquake, a 100 foot tsunami and the coastline dropped several feet. There is about a ~10% chance this will ha…

Not to mention that a very large number of homes in Western Washington are at least 80 years old. The house I live in was built in 1919. It's wood construction and has been gutted/remodeled, but it's also been added onto at least once and has no real foundation, but I think it might be a pier and beam type. An earthquake of large size, 7.0+ will probably cause major damage. For reference, I live near Chehalis, WA.

Re: 1700 Cascadia Earthquake

#78
post #41

Add onto this that many or most of the mountains in the area are active volcanoes that are overdue for an eruption, and the Seattle area could be in for a real bad time over the next 250 years. The projections of a moderate eruption of Mount Rainier (aka Tahoma/Tacoma) include flows reaching all the way to Renton/South Seattle.

“Most” of the mountains are not active volcanos. There are only 4 in Washington: Baker, Rainier, St Helens, Adams but hundreds of other mountains. Rainier is really the only one that poses serious danger to a populated area. Tacoma in particular will be destroyed by lahars alone in a large eruption

There are (at least) five major active volcanoes in Washington. You are forgetting Glacier Peak, an active volcano that is as close to Seattle as Rainier, but not as visible due to its lower elevation.

Re: 1700 Cascadia Earthquake

#79
post #49

Earlier quoted context omitted.

there is never a million people on the oregon coast.

The problem is if the entire west coast adds up to 1 million people at the beach it might make very little difference which state their in. A 7pm July 4th quake resulting in a massive Tsunami would be vastly more deadly than an identical 4am quake the next day.

If there were ever 1 million people heading to the PNW coast collectively, even on 4 July, the PNW would know it. Routes like the 26 out of Portland or the redwood highway in Oregon / California cannot handle that much traffic. The road to Gerlach, NV gets jammed up by Burning Man traffic, so that should give a good estimate of how many people there can possibly be out there.

Also, unlike in California or the East Coast, these are not quick jaunts to the ocean.

Re: 1700 Cascadia Earthquake

#80
post #69

Earlier quoted context omitted.

When the "big one" hits the pacific NW, bridge design is not going to save significant areas from complete destruction. I am talking about the Cascadian Subduction Zone letting go which happens every 200 to 1200 years (41 times in the last 10000 years). The last time this happened, in 1700, there was a 9.0 earthquake, a 100 foot tsunami and the coastline dropped several feet. There is about a ~10% chance this will ha…

Not to mention that a very large number of homes in Western Washington are at least 80 years old. The house I live in was built in 1919. It's wood construction and has been gutted/remodeled, but it's also been added onto at least once and has no real foundation, but I think it might be a pier and beam type. An earthquake of large size, 7.0+ will probably cause major damage. For reference, I live near Chehalis, WA.

Post and pier foundations aren't ideal for earthquakes. In general though, wood performs better than masonry as a quake resistant building material because it can flex.
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