Cascadia: The Earthquake that will Destroy Westcoast America

[Jade Falcon]

So a few comments I've read on YouTube says the ocean could conceivably come all the way inland to I-5 and then some?

Yeah, F- that. Thankfully I live on HW-20 so I can go East if I have to, but I doubt it would be passable with downed trees and landslides.

My elderly parents live in Vancouver in the upper-middle-class suburbs of Cascade Park....they would probably be killed or seriously injured, and especially my mother who is lacking her bladder and takes medication. Or if not that, then cut off for extended periods of time without food, water, or electricity. My father would go insane. HW-14 EB would probably be impassible with the tunnels collapsing.

My sister is almost constantly in crisis for some reason or another, so she'd probably be toast too. The rest of my family lives in California.

Chilling stuff! Definitely don't want this to happen until I'm long dead and dust.

 

[whiskeybill]

I was stationed in Seattle in the mid 80's, and learned the origins of Denny Hill, often called the Denny Hill Regrade. As Seattle was being built, huge amounts of "landfill" were moved from the waters edge, essentially mud flats, to Denny Hill, and now most of modern Seattle is built on this. The bay was dredged as well, and piers were built to accommodate deep water trade vessels. More of the dredge was moved to Denny Hill. Now they realize that a good earthquake will liquefy nearly all of the ground that downtown Seattle is built on. The Cascadia will not only wipe out the port facilities, but Seattle proper will for the most part slide right into Elliot Bay.

 

[NeoBlackdog]

Seattle proper will for the most part slide right into Elliot Bay.

Be still my beating heart!

 

[Provincial]

40-foot high tidal wave. PDX is 18 feet above mean sea level.

A 40-foot high wave coming up the lower Columbia River would back up the fresh water flowing seaward. That means that there would be an ever-increasing amount of water being pushed ahead of the wave, and it has to go somewhere.

As the wave encounters the river water, it will compress the front edge of the wave, probably increasing the height of the wave. The 40 feet height could become much more.

I live at the 475-foot level. A balcony seat!

 

[Stomper]

I was stationed in Seattle in the mid 80's, and learned the origins of Denny Hill, often called the Denny Hill Regrade. As Seattle was being built, huge amounts of "landfill" were moved from the waters edge, essentially mud flats, to Denny Hill, and now most of modern Seattle is built on this. The bay was dredged as well, and piers were built to accommodate deep water trade vessels. More of the dredge was moved to Denny Hill. Now they realize that a good earthquake will liquefy nearly all of the ground that downtown Seattle is built on. The Cascadia will not only wipe out the port facilities, but Seattle proper will for the most part slide right into Elliot Bay.

Seattle has not been proper for decades now.

 

[Stomper]

40-foot high tidal wave. PDX is 18 feet above mean sea level.

A 40-foot high wave coming up the lower Columbia River would back up the fresh water flowing seaward. That means that there would be an ever-increasing amount of water being pushed ahead of the wave, and it has to go somewhere.

As the wave encounters the river water, it will compress the front edge of the wave, probably increasing the height of the wave. The 40 feet height could become much more.

I live at the 475-foot level. A balcony seat!

Cool, you can drop spit-bombs on the floaters-by like a kid does cars on a highway overpass!

 

[SteelheadTed]

An architect friend said the same thing, but used the word "liquify" instead of fall.

Very few architects know much about structural engineering. Liquify is not a word we use to describe building failures. Liquefaction is a phenomenon having to do with soil that losses it's bearing capacity. Soils subject to liquefaction are the exception, not the rule.

There is no way to know definitively which buildings will survive an earthquake. it depends on hundreds of things such as ground motions at each building site, whether it was built on good soil, under what building code the building was designed to and whether it was designed and built well.

 

[ob1]

Buildings built before 1995 will fail in the earthquake.

The oldest buildings at Reed College in Portland were some of the first built with reinforced concrete. At that time, the engineers were very conservative about the strength of this new type of construction. In the 1970's, an engineering student reviewed the design of these buildings and found them quite strong. His summation was "you can set the Hiroshima atom bomb off 100 yards in front of Eliot Hall, and it will succeed in tipping it on its side, but still intact."

Interesting comment since that was around the time Reed put in an atomic reactor.

 

[Provincial]

Interesting comment since that was around the time Reed put in an atomic reactor.

Eliot Hall and the other original buildings were built in the 1920's. The reactor came in 1968. There was a bit of a lag.

 

[The Heretic]

Tsunami detection along the Pacific Ring of Fire gets a boost from new satellite technology

Tsunamis caused by earthquakes, volcanoes or other events can destroy coastal communities around the world, and now scientists at NASA’s Jet Propulsion Laboratory are testing new ways to detect the deadly ocean waves from the far reaches of the atmosphere.

www.foxweather.com

 

[Burt Gummer]

Most tests on the Oregon Coast, specifically done at Cannon Beach, have shown the vast majority of people head to their cars; instant gridlock. Where the only hope is a bee line as fast as you can go to high ground. No durable steel/concrete structures to attempt to get high above, etc.

 

[mrblond]

I was visiting with Oregon Department of Geology guys at a Christmas party years ago. The talk turned to the Cascadia earthquake. They said it would be devastating, with many buildings demolished. Summer would be bad, with fires possibly out of control.

I commented that I thought that much of the Willamette Valley would be worse off in Winter, with the soils saturated. This sent a shudder through the geologists, with all of them referring to "liquification" and pointing out that much of the cities and infrastructure were built on alluvial soils/gravels. Soak these with 100% of their water capacity, then shake, and you get the same effect as putting dry sand in a blender, adding water until it reaches the top of the sand, and turning on the blender.

1985 Mexico City earthquake - Wikipedia

en.wikipedia.org

but on a larger scale.

 

[sobo]

As a civil engineer, I'm glad to see several people in this thread correcting the term "liquefy" to what actually happens, which is soil liquefaction. While the two terms sound similar, and many people think the two phenomena are the same, they're actually two different mechanisms. I had a hard time wrapping my head around the two terms in geotech classes and soil labs in college BITD, but I think I finally got it sorted out...

 

[oremike]

Anybody remember Van-port?

 

[Provincial]

Here is a link to a PBS presentation about what to do in an earthquake in the Pacific Northwest. It is pretty basic, but actually has good facts, mostly presented by two Oregon State University professors.

 

[edzz]

I was stationed in Seattle in the mid 80's, and learned the origins of Denny Hill, often called the Denny Hill Regrade. As Seattle was being built, huge amounts of "landfill" were moved from the waters edge, essentially mud flats, to Denny Hill, and now most of modern Seattle is built on this. The bay was dredged as well, and piers were built to accommodate deep water trade vessels. More of the dredge was moved to Denny Hill. Now they realize that a good earthquake will liquefy nearly all of the ground that downtown Seattle is built on. The Cascadia will not only wipe out the port facilities, but Seattle proper will for the most part slide right into Elliot Bay.

 

[edzz]

Um, I think you may have been misinformed about the Denny regrade. Not quite how it was explained to me growing up by relatives that watched the development of Seattle.

Denny regrade

 

[Alexx1401]

Um, I think you may have been misinformed about the Denny regrade. Not quite how it was explained to me growing up by relatives that watched the development of Seattle.

If it slides away it will be the flushing of that toilet that's been needed for a LONG time.

 

[Provincial]

Denny Hill was cut down. The material was used to level the area below it.

Most flat ground near the water in the Seattle area is dredge fill. This is the area that will liquify.

 

[RVTECH]

Why add the ' IA ' to the word Cascade to make it 'Cascadia' ?

We have a 'Ufologist' here in LaPine who is absolutely enthralled with a stone formation up near Paulina Peak. Its a layout of two people sitting back to back arranged from rocks laid on the ground.

He calls it the 'Cascadia Guidestones' and believes it to be of alien origin and that it is 6K years old and that there may be a 'structure' or something hidden underneath it.

He actually had a You tuber produce a documentary on it called 'The Middle' and it is shown on Tubi.

He claims the place is 'Sacred', and that it is in a National Park ( which it is not - it is near Newberry National Volcanic Monument).

Interestingly someone commented on his video site and said he looked up some satellite imagery history and discovered this did not show up until 2012.

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