[ANSS-netops] ANSS-netops Digest, Vol 36, Issue 7

[John R. Evans]

Yup, that's the one.  Thanks for the kind words, Dave.

(Like the way the attachments are coming as links, Lind -- works on a Mac too.)

Cheers,
John

John R. Evans

-------------------------

650-329-4753 direct
408-209-6219 mobile
jrevans at usgs.gov

-------------------------

Normally at (mail or shipping):
U.S. Geological Survey
345 Middlefield Rd, MS-977
Menlo Park  CA  94025

-------------------------

Intermittently at (mail only):
USGS/ASL
P.O. Box 82010
Albuquerque  NM  87198-2010

Intermittently at (shipping only):
USGS/ASL
Target Rd 10002 Isleta SE
Kirtland AFB  NM  87117

-------------------------

I got nasty habits; I take tea at three.  (Mick Jagger)







--------------------------------------------------



On 29 Mar 2012, at 11:15, anss-netops-request at geohazards.usgs.gov wrote:

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> Today's Topics:
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>   1. Re: L4 3 component mount (David S. Croker)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Thu, 29 Mar 2012 11:13:17 -0700
> From: "David S. Croker" <croker at usgs.gov>
> To: Steve Estes <estes at gi.alaska.edu>,anss-netops at geohazards.usgs.gov
> Cc: sydeen at usgs.gov
> Subject: Re: [ANSS-netops] L4 3 component mount
> Message-ID: <OFD6CA4505.A2A1833D-ON882579D0.00641885 at usgs.gov>
> Content-Type: text/plain; charset="us-ascii"; Format="flowed"
> 
> Hey Steve, that looks awfully familiar.  We took our design from John 
> Evans, who happens to be good buddies with John Rogers.  We do the 
> same for electrical isolation too.  We do not weld our plates 
> together.  I guess too much trouble.  We instead use 4 bolts in each 
> channel to secure them to the bottom plate.  Of note, however, is we 
> work hard to secure the seis cables as close to the cap as possible; 
> for instance, we zip tie the vertical cable to one of the vertical 
> threaded rods and have a cable clamp in the corner of the plate to 
> secure all of the cords.  With even moderate shaking, the cords will 
> start to shake and affect data.  The other big difference is we 
> support the plate on heavy compression springs that fit around each 
> of the mounting bolts.  Then, we compress the springs greatly so 
> there is not too much play left, but enough to make the leveling 
> process easy with a socket.  The design is such that you only need to 
> adjust the west and south bolts, and once the two horizontals are 
> level, by default the vertical will be level also.  This design has 
> worked very well for us with no discernible differences in data seen 
> in side-by-side testing with a direct buried L4 (that's with John 
> Evans comparing seismograms too, and if you know John, he is as 
> careful as they come).
> 
> Attached are a picture of the plate and our diagram.  The black box 
> in the picture is where we terminate the seis cords and insert the 
> S+T resistors, with one 3-pair individually shielded cable out to the 
> digitizer.  Hope this helps.
> 
> Dave
> 
> At 03:15 PM 3/28/2012, Steve Estes wrote:
>> Three component mount for L4C.
>> Leveling of the mount is accomplished by using washers between the 
>> mount and concrete.
>> Electrical isolation, if desired, is accomplished using slotted PVC 
>> pipe for the horizontals, and a PVC plate on the top and bottom of 
>> the vertical.
>> I was introduced to this design by John Rogers of Alaska Section of 
>> USGS in about 1993.
>> 
>> Regards,
>> Steve
>> 
>> 
>> 
>> 
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> End of ANSS-netops Digest, Vol 36, Issue 7
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