Subject: [IGSMAIL-4652]: RE: [IGSMAIL-4642]: IGS00 (v2)
From: "Ferland, Rémi" <[email-masked]>
To: 'Jeff Freymueller' <[email-masked]>
Cc: "[email-masked]'" <[email-masked]>
Date: Thu, 9 Oct 2003 16:10:23 -0400

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IGS Electronic Mail      15 Oct 14:44:48 PDT 2003      Message Number 4652
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Author: Rémi Ferland

Dear Jeff et al.,

	The average displacement  and transient displacement were accounted
for by starting a new estimation. With most of the transient displacement 
occurring over about two weeks, it should have little impact on the 
cumulative solution. Also you pointed out, because of the
relatively short time span and post seismic effects; the new velocity 
was not reliable.
So, the estimated pre(1) and post(2) seismic event velocities were 
combined using all the available covariance information.

Before they were combined, their respective velocity w.r.t.
the NOAM plate:

 Code Pt Soln    d. Lat  d. Lon  d. Hei  d.VLat  d.VLon  d.VHei
                   (mm)    (mm)    (mm)  (mm/y)  (mm/y)  (mm/y)

 FAIR  A    1                               -1.9     1.9    -3.0
 FAIR  A    2                              -24.0    12.7     2.1

the first segment contains several years of data, while the
second one is limited to about one year.
After their velocities were combined, the new velocity minus
the plate motion model was:

 Code Pt Soln    d. Lat  d. Lon  d. Hei  d.VLat  d.VLon  d.VHei
                   (mm)    (mm)    (mm)  (mm/y)  (mm/y)  (mm/y)

 FAIR  A ----                               -1.9     1.9    -3.0

The pre(1) earthquake velocity dominates the combination. Essentially,
the FAIR post(2) solution proposed is approximately the average
post(2) position solution with the pre(1) earthquake velocity.
This assumes that the pre/post seismic velocity are approximately
the same. As you pointed out, the station may not have fully returned
to its steady state. I will keep a close eye on it!

Note, recent residuals for the station can be found in:

http://igscb.jpl.nasa.gov/network/site/fair.html

The station is located in a remote area and is also collocated
with VLBI. It had also been used since the early days of IGS, so
important to connect the various realizations. Essentially, the
station had many of the desired attributed... except for last year
earthquake.

Thanks for the warning

Best Regards,
Remi,

R=E9mi Ferland
[email-masked], 613-995-4002,  fascimile/t=E9l=E9copieur =
613-995-3215
Natural Resources Canada, 456-615 Booth Street, Ottawa, Ontario K1A 0E9
Ressources naturelles Canada, 456-615 rue Booth, Ottawa (Ontario) K1A =
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