earthquake

[Chuysmom]

Wonder what's up with Mauna Kea. Hm.

Carrie[?]

[TomK]

I remember reading a paper not too long ago that suggested earthquakes under our volcanoes that were deeper than 13 KM (such as this cluster) were due to ruptures in existing faults caused by the weight of the volcano itself and the flexure in the rocks below (i.e., the lithosphere which is quite brittle if I remember my old geology classes correctly). If that's correct then it's unlikely to be volcanic activity which would be quite a relief given where I work!

Tom
http://apacificview.blogspot.com/

[Royall]

Did you feel it up at the top Tom? Whatdoes tremors like that do to the equipment?

Royall

Hale O Na Mea Pa`ani

[Royall]

Interesting to note, I've watched the earthquake web that I posted, everyday for almost 6 years. This is the first time I can remember seeing so many quakes (28 as I type this) so closely packed in such a short time. It will be interesting to find out what the people that know these thing in detail have to say about it.

Royall

Hale O Na Mea Pa`ani

[TomK]

Royall,

I was in Hilo at the time - I felt the first earthquake but only just - but people at the summit certainly felt a jolt or two. For my telescope (UKIRT) what generally happens with anything over a mag 4 earthquake on Mauna Kea is that the telescope gets knocked off its axis slightly and that's what happened this afternoon. Try and picture a massive telescope sitting on a mount and then when things shake it gets shifted slightly on that mount (we could be talking a millimetre or two, probably less!). The result would be that we would have no idea what we're pointing at because now everything is out of alignment. We have shear pins (small metal rods) on the mount that break if this happens indicating a problem. One of them broke today so the telescope had to be moved back into position and so far things seem to be working OK. There's a video out there somewhere of someone doing this realignment (it's hard work at 14,000 feet!) but can't find it right now, I'll post a link if I find it.

Can't really speak for the other telescopes but they are likely to suffer similar problems although some are more prone to this than others. They all have sensitive equipment as well of course so any shaking could damage that, but I would only expect that with a more series earthquake - remember most of the equipment had to survive the drive to the summit which is not the smoothest trip in the world!

Tom
http://apacificview.blogspot.com/

[TomK]

The video I was thinking of is here - http://youtu.be/yn5pHqENfJA - it was made by a visiting astronomer at the University of Nottingham in the UK (I worked there many years ago!). The bit relevant to an earthquake starts at around the 5 minute mark but the whole video is interesting for those wanting to know what goes on at the summit!

Tom
http://apacificview.blogspot.com/

[Chuysmom]

Thanks as always, Tom. I LIKE your explanation of possibilities better than my all-too-vivid imagination! LOL! []

Carrie

[Royall]

Thanks for the video link and the information Tom. I guess it is a whole lot better to have the shear pin part and let the telescope move a around a little rather than having it bolted down tight and shake it's self to pieces!

Royall

Hale O Na Mea Pa`ani

[TomK]

Carrie - no problem at all, I enjoy sharing a little bit of my life and work with others as it's quite an unusual job and not something many people see even those living here. Let's say that all bets are off with a major earthquake though!

Royall - you hit the nail on the head and that's exactly what the shear pins do. Boris, the guy in the video, has one or two minor facts wrong but that's understandable since he doesn't work here and doesn't really detract from his story, but the main purpose of those pins is to tell us that something has shifted and therefore we need to fix the problem before operating the telescope again.

I've been lucky in all the years I've been here - I've never had to deal with those shear pins while I was at the summit, and seeing Boris grunting like that I think I've been very fortunate!

Tom
http://apacificview.blogspot.com/

[oink]

That was an interesting video, although the guy was a bit hard to understand as he talks kinda funny.

Pua`a
S. FL
Big Islander to be.