West Coast USA: Pay Attention, Cascadia May Be Ready to Rupture

reply to post by Char-Lee


John Vidale is the director of the Pacific Northwest Seismic Network (hope I have the title correct) and he writes an interesting blog found here

Seismo Blog

I have learned a lot by reading it. His member profile says he is from Seattle. Maybe he is just on a summer vacation or really busy...

It sound like you are close to the coast, so I see why you would want to be aware of what is going on in that area. I am further away, nearer to Portland, but I still watch the earthquakes.

However, TrueAmerican and Olivine and others know much more about this than I do. And that is an interesting question about your well, maybe someone else here will have an answer. Maybe the swarm will end soon.

reply to post by PacificBlue


Still out of town, but I only check in here every week or so in any case. The swarm is interesting, and I wouldn't trust any of the depths, and we have no focal mechanisms of which I'm aware - the quakes are too small.

But the quakes are located about the right latitude and longitude. The generic rule of thumb, which I'd apply here as we don't know anything better, is 1 in 10 chance of an event bigger than the original event within a few weeks, and of the bigger events, most would be only slightly bigger. So the worry level about each M3 event is very low.

If we had an M6 or an M7 just offshore, that would be a different story.

reply to post by JohnVidale


Thank you so much for the reply. I just did not want anyone to worry about this swarm, as it did not seem like it was something to be really concerned about. And we are very lucky to have an expert available to answer questions, and I am sure you are very busy, so thanks again. I have learned many new things by reading your blog and also your posts in the quake threads.

The article mentioned below, which may or may not be accurate, seemed like it may have caused people some concern. That is kind of why I replied. Usually I just read and do not post, as I am still learning about this subject. Actually, I was out at the coast today, and it seemed just fine, and kind of quiet.

My only comment about this article, is what does that mean " But no one would stick their neck out and say what they think they mean". I was not sure what answer they would be expecting. No one can really predict what will happen, just my opinion, and I do not know much.

Hopefully people may read your response, as that is a really good explanation. No reply necessary.

Originally posted by Char-Lee
reply to post by TrueAmerican

 

“Normally, the Cascadia Subduction Zone is very, very quiet,” Goldfinger said. “Chatter I’ve heard among seismologists, they think they’re pretty deep in the Juan de Fuca slab. But no one would stick their neck out and say what they think they mean.”
www.currypilot.com...

the article here has gotten many people spooked. We have a friend who decided to move right now, she put her house up for sale based on this alone!

reply to post by TrueAmerican


Thanks for always letting people know to be prepared, and for all the information. I am not too close to the coast, but close enough to be affected by possible infrastructure issues. So I like to keep an eye on things, but not panic.

But you are right, it will happen someday, just hope I am not around to see it.

I was out at the coast, and got to see some tsunami debris. It is mostly wood, but that is so strange to think that it came all the way from Japan and landed on the Oregon coast. Things do wash up now and then, like shoes that fell off of ships and other things, but there is so much debris, and it will be coming for years.

Also, it felt a little bit sad, when I thought about what happened, and why all the wood was there. However, there have been some people that found personal property, and it is being returned to Japan, so that was good to hear.

Mount Tongariro in the North Island of NZ just errupted a short time ago; went from Level 1 to Level 2 an hour ago. White Island off the Bay of Plenty went from Level 1 to Level 2 yesterday.

www.nzherald.co.nz...

From that article:

But no one would stick their neck out and say what they think they mean.

“If we have a great earthquake in the next week, I’ll tell you the significance (of the cluster of quakes last week),”
Goldfinger said. “Then, they will have been foreshocks. No one can say.”

Yeah right. While I do stick my neck out and take all the heat for it from the haters.



So tell us John how often there are swarms of quakes like this off the Oregon coast in that spot.

reply to post by TrueAmerican


“Chatter I’ve heard among seismologists, they think they’re pretty deep in the Juan de Fuca slab. But no one would stick their neck out and say what they think they mean.”

That's ridiculous. I located several of those earthquakes for the PNSN myself. We just have only a few stations nearby, they're all on one side, and consequently we can't estimate the depth. There should be some OBSs recording the earthquakes on the seafloor, which will eventually help improve the location, but they do not transmit data back to land and will not be picked up for a while. In the meantime, we'll have to wonder about the depths.

"how often there are swarms of quakes like this off the Oregon coast in that spot."

We haven't seen a swarm like this there before. But we also have been continually improving our network in the area, so we wouldn't have seen a similar one 10 years ago. Bottom line is that it ever so slightly raises the odds of a big quake in the area, but not nearly enough to matter for any practical purpose. And as the swarm has died down again, there is even less cause for worry.

2.1 just hit offshore Washington/Oregon border, in a suspicious spot.

earthquake.usgs.gov...

Isn't that 2.1 right in part of the locked, accretionary zone?

reply to post by TrueAmerican


TA, I'm suspicious of that location and magnitude. This event has not been reviewed yet. It registered on seismos all across the US (eventually).

reply to post by Olivine


Yeah, believe me I hear you. I am waiting for a dolphin to come in close to shore, put that quake on its back, and carry it out to sea near the plate boundaries any time now...

reply to post by TrueAmerican


Your funny.

PB024

There looks to be about 20 seconds between P and S-waves. What's the rule of thumb, 8 km/sec? So maybe 160 km away from this station?
It also looks like there was a second earthquake 18 minutes after the first.

reply to post by Olivine


Just a naughty jab at John, that's all. I know the problems with the locations off the coast.

I got P->S differential at about 14.9 sec, putting that at roughly 140 km or so from station...I think...

EDIT: wow, guess that dolphin must have grabbed that quake and dove down deep, never to be seen or heard from again. Cause that 2.1 is gone... *poof*

Originally posted by Olivine
reply to post by TrueAmerican

 

TA, I'm suspicious of that location and magnitude. This event has not been reviewed yet. It registered on seismos all across the US (eventually).

Aww thank you, i had posted about this in another thread, and someone did mention the 2.1... i had been monitoring several stations across the country on GEE and thought it was weird how it showed up, the P ways showed up on numerous stations eventually.. I had myrtle point oregon pulled up and it seemed to be closest to that location, but i had nothing north of there pulled up, but this makes perfect sense, and answers my question as to what caused the p waves to hit lots of distant stations across the country.... so now the question is why did it?

Gone?

So what was it; some sort of super secret military detonation?

Something made the earth jiggle, and I would like to know what it was...

Weird.


ETA...
Well, LDEO shows a Mag 5.4 several hundred kilometer off the Oregon coast.

2012 8 8 17 45 36.0 44.00 -130.00 33.0 5.4 OFF COAST OF OREGON

reply to post by Olivine


No, it's not gone you have to use the old USGS page for the US
Here

I don't think that can really happen like that way in the movie where parts of land slide into the ocean carrying cities with it. I don't think that can happen in real life. No way can i ever see that happening at all. Now cascadia, how big is this and has anyone noticed activities below the serface of the ocean?

Originally posted by Olivine
Gone?

So what was it; some sort of super secret military detonation?

Something made the earth jiggle, and I would like to know what it was...

Weird.


ETA...
Well, LDEO shows a Mag 5.4 several hundred kilometer off the Oregon coast.

2012 8 8 17 45 36.0 44.00 -130.00 33.0 5.4 OFF COAST OF OREGON

edit on 8/8/2012 by Olivine because: additional info

edit on 8/8/2012 by Olivine because: (no reason given)

This is blowing my mind..... Where did it go? Lol

reply to post by MamaJ


It finally resurfaced, MamaJ!
USGS Mag 4.9 offshore Oregon

Originally posted by Olivine
reply to post by MamaJ

 

It finally resurfaced, MamaJ!

USGS Mag 4.9 offshore Oregon

Hmmm... Lol.... Yeah just saw it and was coming to post.

reply to post by MamaJ


Yes, it was a littler event followed 30s or so later by the M4.9, not a P wave followed by an S wave. The S wave was quite a ways back, and associated with the M4.9, not the smaller event that made the initial P wave.

Complicated, and it took us a few minutes to take down the automatic location and magnitude of the 2.1 to replace it with the right solution. It also took the Colorado USGS folks a few minutes to get it right.