OT Speaking of Earthquakes, is Oregon Asleep at the Wheel?

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Oh boy! Fear Mongering again!

While the Oregon coast can and has been hit with Tsunamis, it is extremely questionable that one generated by the Cascadia subduction zone has ever created one. There is no broad shallow plain to be up lifted between the Oregon shore line and the Cascadia Fault. The Hecta bank off the central coast is somewhat but this is well inside the Fault out there a 130 to 150 miles off shore with water depths of 7000 - 9000 feet.

Dr. Van Dorn's Oceanography and Seamanship book from when he was Director at Scripps shows that all Tsunamis known over the last 300 years have been generated by uplifting of the sea floor covered by waters of less than 1000 feet.
This makes very good sense, as a Tsunami is the result of a displacement event that reaches the surface of the sea. When you consider water will move and accelerate to equalize pressure change at the rate of the acceleration of gravity, it is nearly impossible to expect the sea floor to rise at the rate needed to cause a surface disruption in 7000 feet of water. Extraterrestrial bodies may enter the sea at this rate easily enough, but what could raise the sea floor at that rate? Not known to happen.

I sort of think of the Tsunamis coming out of a big gold pan that has been sloshed in a direction. Like the broad plain off the coast of Japan, out to the subduction zone there. Starts at about 100 fathoms deep out 100 miles offshore. Damn it work good!
That is one big slosh pan. We have the subduction zone, but lack the pan.

We are very vulnerable to Tsunamis generated in Asia, the Aleutians, or the Gulf of Alaska.
Drove through Rockaway last week, thinking, Damn! I wouldn't want to live here!
 
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MarAzul said:
Oh boy! Fear Mongering again!

While the Oregon coast can and has been hit with Tsunamis, it is extremely questionable that one generated by the Cascadia subduction zone has ever created one.
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I don't know, actual scientists seem to disagree with you on that.

But best case, if you are right, the only advantage is that we won't have an earthquake and a tsunami at the same time. We're still in danger from both individually.

barfo
 
barfo said:
But best case, if you are right, the only advantage is that we won't have an earthquake and a tsunami at the same time. We're still in danger from both individually.
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Nearly correct. The tsunami is not likely to be caused by the same earthquake that might wipe us out.
 
barfo said:
I don't know, actual scientists seem to disagree with you on that.
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Yes, they project one to happen. That is a tsunami being generated by massive earthquake from a shifting of the Cascadia fracture. But I know of no evidence where a tsunami was generated in this way. The math just doesn't work.
Back when I worked with Dr. Van Dorn, we discussed this. He decided to leave it out of any detail on tsunamis. Just could not prove it could not happen and besides, the tsunamis can come from a number of places to the North West coast.
 
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Lanny said:
If the legislature passes this I will be astounded. Is there anything more stupid?
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I love this reference to bad math!

"What makes arguments like Gomberg’s particularly maddening is that they aren’t merely based on bad morals; they’re based on bad math. No matter how you crunch the numbers, it’s impossible to imagine any road to financial security that runs through the inundation zone. In places where there’s truly no other evacuation option available, it’s obviously better to have a tsunami-resistant building than nothing at all."

The bad math come in especially strong where your math leaves you with the impression you will have no warning. This would be true if it were likely generated on the Cascadia Fault. But not so correct if it is in the Aluetians.
Not as written in the articale though, and I don't think the Democrats that passed this nor the Governor that signed it, actually considered any of the math.
 
What is the difference between a Cascadia (local) tsunami and a distant tsunami?
An earthquake on the Cascadia subduction zone, a 1000-km- (~600-mile-) long fault zone that sits off the Pacific Northwest coast, can create a Cascadia tsunami that will reach the Oregon coast within 15 to 20 minutes. Massive earthquakes of magnitude 9 or greater have been generated on the fault zone that probably produced strong shaking that endured for several minutes. A destructive tsunami can follow moments later.

A distant tsunami produced by an earthquake far from Oregon will take 4 or more hours to travel across the Pacific Ocean, usually allowing time for an official warning and evacuation, if necessary. A distant tsunami will be smaller in size and much less destructive, but it can still be very dangerous.
 
Have tsunamis hit the Oregon coast?
Yes. Tsunamis triggered by nearby earthquakes offshore Oregon as well as distant tsunamis caused by earthquakes across the Pacific Ocean have struck the Oregon coast. The last Cascadia tsunami, triggered by a Cascadia subduction zone earthquake, occurred in A.D. 1700, and left an indelible mark in Native Tribal legends. Damaging tsunamis from distant sources reached Oregon’s shorelines as recently as 1960 and 1964.
 
Will a tsunami strike again?
Yes. Between 1854 and 2008, 21 tsunamis produced by earthquakes around the Pacific Ocean basin have reached the Oregon coast. Wave heights of four of these distant tsunamis reached 1-5 m (3-16 ft), causing damage to coastal communities and in one event, five deaths. Geologists believe we are overdue for a Cascadia tsunami triggered by a shallow, undersea earthquake offshore Oregon. The forecast comes from evidence for Cascadia earthquakes and tsunamis that have impacted the Oregon coast every 240 to 500 years, on average.
 
Who is at risk?
Communities along the Pacific coast and along estuaries are at greatest risk. A nearby earthquake could drop the low-lying regions of the coast several feet below sea level. The highest tsunami waves could reach 25 m (80 ft) and severely flood coastal communities near beaches, bay mouths, and low-elevation coastal plains. Oregon’s at-risk population is approximately 40,000 on the outer coast, excluding tourists and visitors that seasonally swell the population many fold.
 
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@MarAzul so many of your posts remind of Harry Truman, owner of the Spirit Mountain Lodge on Mt St Helens.
 
SlyPokerDog said:
@MarAzul so many of your posts remind of Harry Truman, owner of the Spirit Mountain Lodge on Mt St Helens.
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Ha! Well take it as you will Sly. But remember, Old Harry was wrong. I don't think you can prove me wrong.
 
MarAzul said:
Ha! Well take it as you will Sly. But remember, Old Harry was wrong. I don't think you can prove me wrong.
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Nobody could prove Harry wrong either, up until a minute or two before his death.

barfo
 
SlyPokerDog said:
BTW, you do realize that not all Tsunami's are caused by earthquakes and undersea landslides.
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Most are caused by an uplifting of the Sea floor causing a displacement event in the basin. But in some cases it is more the an just a displacement event, read the Gold pan sloshing. That was the one most recent off Japan. Just slosh up a monster wave over a plain 100 fathoms to 10 fathoms deep. Like a big pan where the outside tilt up 20 feet in 15 seconds.
 
barfo said:
Nobody could prove Harry wrong either, up until a minute or two before his death.

barfo
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Well then do the math, show us how and what velocities of up lift you will need to create a surface disruption in 7000 feet of water. Harry didn't give you any clues.
 
SlyPokerDog said:
Not me.

Dr Van Dorn.
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Ah! a big meteor?

I think I indicated this is possible. Extraterrestrial body. But then that doesn't have squat to do with Cascadia.

PS Maybe I should have said simply terrestrial body.
 
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MarAzul said:
Ah! a big meteor?

I think I indicated this is possible. Extraterrestrial body. But then that doesn't have squat to do with Cascadia.
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No but it does mean that we should not build police stations, fire stations, hospitals, nursing homes, or schools in tsunami zones. They should be built in the clearly marked evacuation zones along the coast. Then there is greater prevention from multiple disaster scenarios.
 
SlyPokerDog said:
No but it does mean that we should not build police stations, fire stations, hospitals, nursing homes, or schools in tsunami zones. They should be built in the clearly marked evacuation zones along the coast. Then there is greater prevention from multiple disaster scenarios.
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Now you will get no argument from me here. Like I said earlier in this thread about driving through Rockaway. I would not live there! Same when I was looking for a place in Bandon, No way down on the lower plain. I am up on the hill near the top at
about 200'. Since I have live there now quite sometime, I discover a distinctive layer about 2' down about 4 to 6" thick that probably was laid down by a tsunami, who knows when. It is at about the 155' level on my property and less, not above height.
I doubt it was a Tsunami that reached that high though, as I expect the whole property has raise considerable since it was laid down. The uprising of the west coast continues from Cascadia Eastward, slowly but surely.
 
SlyPokerDog said:
No but it does mean that we should not build police stations, fire stations, hospitals, nursing homes, or schools in tsunami zones. They should be built in the clearly marked evacuation zones along the coast. Then there is greater prevention from multiple disaster scenarios.
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BTW, this little discussion is just about like what Van Dorn and I had nearly 45 years ago now. So tell me again about how I remind you of Harry?
 
Stevenson said:
Just like actual lawyers disagree with his constitutional "analysis."
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Yes, well many subjects and especially specific questions where disagreement is very possible with most of us. One I had with a well known Naval Architect some years back. He reviewed my plans for the MarAzul, as I requested, and came to the conclusion that such a craft could not actually be constructed. My son was there at the time when he delivered the hard news. I thanked him and found a graceful way to exit. My son said, Dad! What Now???

I said not to worry. We just found out he doesn't know how to do it. We do.
 
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