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Thanks Mark (and others). All good comments. Looks like we
will always have to trade ease and cost of installation and maintenance
with data quality. And accessibility (ie, how long does it take to
uncover the vault when you need to and can you get the lid off after its
been sitting in the soil for 3 years). <br><br>
Paul Bodin shared a couple thoughts:<br>
"That said, based on my previous experiences and not ever having
used a Tcompact, I nevertheless think that direct burial is the most
likely to be successful. i.e., narrow borehole as deep as you can
conveniently get (1-2 m?), packed in sand. If you put them in a tube, I'd
argue for a fairly compliant material - i.e. pvc rather than steel---and
something with a low coefficient of thermal expansivity."<br>
He also included a rough draft of a paper he wrote and submitted to BSSA
on "some of the sad facts we've learned about long period
seismometry and vault design over the past year." With his
permission, I can forward it to everyone.<br><br>
Dave Drobeck chimed in with similar thoughts as Mark and I, and similar
concerns that maybe our vaults have not been as thoroughly tested as they
perhaps should be. Sounds like a perfect task for Bob. Part
of the problem is that no one vault is appropriate, or even possible, at
all locations.<br><br>
The difficult thing the NCSN is facing for this summer is how to install
a C-Trill (or is it Tcompact, or Trilco?) in a location where metamorphic
quartzite bedrock is right on the surface and the Forest Service needs us
to be as discreet and low-profile as possible (forget a backhoe).
<br><br>
Mark, that's a cute little vault you have in the attachments. Can
you point me to a link that shows me what it is? I assume it's
water tight? Is the bottom removed?<br><br>
Thanks again,<br>
Dave<br><br>
At 09:58 PM 7/19/2011, Mark E. Meremonte wrote:<br>
<blockquote type=cite class=cite cite="">Hi Dave,<br><br>
For 6 months to a year we use the small vault systems we developed for
portable systems: see attachments. For the portables we try
to install insulated vaults at least 6 inches below the
surface. However, for permanent install I would not install
less than a foot below the surface; or, if necessary, we mound at least a
foot of soil over top of vault if less than a foot below
surface.<br><br>
For permanent I will probably be using a smaller version of our regional
vaults with sandblasted glass bases and using insulation. See
<a href="ftp://ftpext.usgs.gov/pub/cr/co/golden/hazards/Eq_Effects/Vaults/Regional/5_Vault_CMG3-MEMS.jpg" eudora="autourl">
ftp://ftpext.usgs.gov/pub/cr/co/golden/hazards/Eq_Effects/Vaults/Regional/5_Vault_CMG3-MEMS.jpg</a>
<br><br>
Yes, I believe some tests should be done on temperature effects.
Similar to other BBs, they should be insulated to stabilize temps.
Sounds like an experiment for Bob Hutt at ASL.<br><br>
Some thoughts and Regards,<br>
Mark<br><br>
At 15:20 7/19/2011, David S. Croker wrote:<br>
<blockquote type=cite class=cite cite="">Hi All,<br><br>
Simple question with a potentially longwinded answer (simple answer
preferred): What kind of vault installation do you do for permanent
Trillium Compact sites? Full-blown vaults with lots of insulation,
slightly reduced scale vaults with a little less insulation, or simple
small scale tubes buried a couple feet down with minor insulation?
How do they respond to temperature changes?<br><br>
Thanks for any insight you might have.<br><br>
Dave<br><br>
__________________________________________________________<br>
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