reply to post by mrsdudara
I know you said you haven't read the whole thread, so perhaps you don't understand the basis of it. This has turned out to be a documented 'event' by
the PNSN that has so far been theorized as a glacier stick-slip. There are three other documented cases in 1990, 1998 and 2010. This has been going
on for about three weeks now. The last few posts are about a marked change in the activity. If you get some more time later to better explain what
you are referring to, that would be great. Certainly, when you speak of a 8+ quake, you mean somewhere else in the world, because there has never
been a 'documented' one here that could be seen on a seismometer...the nearest would be the last mega quake about 300 yrs ago, but the only way they
nailed down the time-frame was because of the tsunami in Japan from it.
I have NEVER seen a seismo for Rainier 'solid' (unless from an equipment failure). It would be great if you could find an example.
Anyways, I got a response from PNSN (they are really great about answering questions). Her best, educated guess is that it was possibly an ice
avalanche, caused by all the recent snow. I guess there was a documented case of the ice 'chattering' as it went down up at Baker in the past...but
this of course is in the reverse. if you look at the seismos, It appears like there was some sort of slide or 'burst' and then the 'chattering'.
PNSN even provided me with a paper on this phenomenon (centered around a study at an alaskan volcano).
This might sound stupid, but I really want to make sure that I souce this article right. I got this document in a PDF format...so I saved the best
image of the seismo example as a picture so I could share it with you, but I have to source it and give credit. I did a search on line for the
document, and found the abstract with the link provided, to get the full document. I hope that is enough. So, here is the image, showing the
'chatter' previous and building up to an avalanche (click to enlarge and you will need to zoom in to see it)
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Here is the basic summary:
Each of the avalanches was preceded by up to 2 hours of seismicity believed to represent the initial stages of failure. Each seismic sequence
begins with a series of repeating earthquakes thought to represent slip on an ice-rock interface, or between layers of ice. This stage is followed by
a prolonged period of continuous ground-shaking that reflects constant slip accommodated by deformation at the glacier base. Finally the glacier fails
in a large avalanche.
So....while the seismos look somewhat similar, the obvious problem with this is that what we just saw is backwards.
Does that mean it can't be the culprit? Well, no, because no one really knows for sure what is going on or what is even possible. I supose all we
can do is keep watching and see what, if anything else develops. Most definitely interesting though.
I think the best thing we could do right now is listen to it. SO...if anyone wants to or can take that task on....go for it!!!!!
18-1-2012 by westcoast because: (no reason given)
edit on 18-1-2012 by westcoast because: (no reason given)