Posted on 12/05/2024 12:23:07 PM PST by rottweiller_inc
"No tsunami danger presently exists for this area," the National Tsunami Warning Center said Thursday.
(Excerpt) Read more at yahoo.com ...
Aha, finally found the 7. That is not a user friendly site.
M 7.0 - 2024 Offshore Cape Mendocino, California Earthquake
Dunno this is first I knew about it
This is a closer view of the BC-WA-OR-NorCal offshore Cascadia subduction Zone fault region. The Pacific floor tectonic plates are moving locally to the east, being forced down in a curve just off the coast. That is the long massive curve near the shoreline - where the plate bend down and begin melting. Further inland, that melted masses of water-filled pacific plate rock and sediment get liquid enough to bubble up through the contiental plate rock and form the rown of volcanoes abovbe 30-50 miles inland.
Further offshore though the still-solid rocky plate is moving (relatively) east as three different masses moving as three parallel surfaces.
The borders between the three small plates are the fault lines aimed west-east towards the shore. Quakes on the borders are side-slip earthquakes. Because one side is moving “sideways” compared to the other side.
Further south, on the San Andres fault for example, the fault line is also a side-slip earthquake. But onshore and far more visible since those earthquakes are underneath people. The danger of a sideslip earthquake offshore at this particular position is that it means the ultra-dangerous downward sudden massive quake is no longer being locked up by stresses and resistance in the side-slip edges of the tectonic quake.
👍👍👍
Well, of course, it’s only my opinion.
But...given the population density around the faults I mentioned, I think the death and dislocation would be far greater.
But, as I said, that’s just my opinion.
In the early 90’s I was supporting an Air Defense exercise at a small National Guard base just south of Astoria, OR. At the end of the exercise 2 B1’s overflew our command post breaking sound barrier.
A few miles south of us was the town of Seaside, when they heard the sonic booms they initiated their tsunami drill and evacuated the city.
Good time was had by all.
You are correct - For a Mag 6, maybe a Mag 7 on the San Andres or other inland fault.
But. Up north, on the Cascadia Subduction Zone offshore quakes, there are almost no “inland” earthquakes at all until the BIG offshore Mag 8 or Mag 9 earthquake trips off.
In fact, since no earthquakes were felt “at all” between the first settlers in 1830’s and 1995 when the massive coastal subduction traces were found of the 1703 Mag 9 were found in the coastal forests, people though the BC-WA-OR coast was fault-free.
We drove that coastline last September from just south of Cape Mendocino to where the road turns inland to Petrolia. Very scenic, with a black sand beach.
This are the past very large earthquakes up and down the Cascadia Zone rezion.
https://projects.oregonlive.com/maps/earthquakes/timeline
We are NOT “overdue” for a Mag or Mag 9 earthquake up there. Rather, we are “due, on average, about right now” for a Mag 8 or Mag 9 earthquake.
324 years since the Indian tribes were wiped out in 1700, and an “average interval” of between 300 to 500 years.
Mine went off which is why I googled the story and post.
San Andreas and its accompanying faults are side slips..or strike slips.
Same thing. Somo of us like to use the more understandable term “side slip” instead of the more geological term strike slip.
The fault moves sideways horizontal in a quake.
Also, side slip earthquakes dont tend to shake far away like a subduction quake.
If a large 8.0 or 9.0 subduction break were to happen, it would be felt 100s of miles away from the epicenter. The damage would be catastrophic.
We would most likely feel it very slightly here in NW AZ...depending on the geological mAkeup of the region between here and there.
Where you appear to be? Your gonna really experience something that will scare the heck out of you.
Some years ago I did a lot of digging into the Juan de Fuca earthquake situation, the one from 300 years ago dropped the coastline a bit, and since there were no “civilization” here, it didn’t have destruction that would happen now. Which, as you say, would be unimaginable. We’re on the east side of the Coast range, so no tsunami here. I figure we’d be totally on our own for a long, long time. Wood heat, well with large storage tank, generators, etc. I am not fond of earthquakes and if it holds off until I leave the planet I won’t mind. :😎
I read Indians in the very north (WA state?) weren’t wiped out but had oral history of that EQ and tsunami.
THanks for link.
I need to say that myself being a engineer and that many of my friends are retired geologists.
But, all of them are in paleogeology. Meaning they are in the study of ancient geological investigations. Thats where i get my information from since we keep in contact.
The one focus of these guys is historical volcanism.
We have discussed the Cascadian zone often and what it would mean concerning the string of active volcanos along the line there. That is where those volcanos get their material from they erupt.
You should have seen my email when the Tonga volcano went. They really got excited.
Did you know that the tsunami created by that blast was WAY higher than the one the 2011 japan earthquake created. Many Meters higher.
Keep yourself prepared. It may come to the point that the only one you can rely on is yourself and those immediately close to you.
Volcanos can be predicted to a point. Earthquakes can not.
Thanks for info, I remember reading about Tonga blowout. Wasn’t that what cause “the year without summer” in the US in the 1800s some time? THere’s volcanic rock all over the place in OR.
I have only heard of Indian oral traditions of the far older explosive blowout of the Crater Lake Caldera. Also of rock slides damning the Columbia River upstream of Portland Oregon.
Tales of the Jan 30 1700 offshore earthquake and its tsunami destruction up and down the BC-WA-OR coast could only be carried by (be created by?) surviors of tribes who were back from the coast and inland, uphills that particular night. But, even with no coastal tribe surviors, in the 104 years between the tsunami and the arrival of Lewis and Clark to the coast, it would seem near-certain that people would return to the rivers and bays from inland. Or remember tribes that used to be on the coast.
I do not recall their reports mentioning past tribes, but rather pointing that there were no tribes nor fishing villages. And, obviously, no ports or European colonies either.
We’ve been having some minor quakes here as it is.
Same here for the last 2 months not happy with that
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