Subject: Re: ILRS observation of shift in EOPs (fwd)
From: Martine Feissel-Vernier <[email-masked]>
To: [email-masked]
Cc: Chopo Ma <[email-masked]>
Date: Fri, 21 Jan 2005 08:43:46 +0100 (Paris, Madrid)

Dear colleagues

You'll find hereafter a mail from the new Chairman of the IERS Directing
Board, Chopo Ma, to the Analysis Coordinators of the IDS, IGS and IVS, and
other IERS members concerning a claim from ILRS that they see a 4-5 cm
move of the Earth's pole of inertia at the date of the Sumatra earthquake. 
I encourage you to participate in its assessment, as proposed by C. Ma.
While a move this size may be difficult to assess with the Doris data, we
have here an excellent opportunity to test the current Doris capability
concerning polar motion.

Best regards.
Martine Feissel-Vernier               
IDS Analysis Coordinator
---------- Forwarded message ----------
Date: Wed, 19 Jan 2005 17:18:26 -0500
From: Chopo Ma <[email-masked]>
To: Ron Noomen <[email-masked]>, C Ma <[email-masked]>
Cc: Gerd Gendt <[email-masked]>, A Nothnagel <[email-masked]>,
    M Feissel <[email-masked]>, [email-masked],
    [email-masked], [email-masked],
    [email-masked]
Subject: Re: ILRS observation of shift in EOPs

Dear Ron,

The ~1.5 mas jump in ypole in the ILRS combined EOP series shown in Figure 
1 of the attachment is certainly interesting.  A combination from all space 
geodesy techniques or a detailed comparison would enhance the reliability 
of the result, and this could be coordinated by the IERS or by the 
technique analysis coordinators.  However, it is most important that the 
analysis results be properly interpreted, and I wonder if the comparison 
with USNO finals.daily is the best way to see a break.  It might be useful 
to directly compare the SLR, GPS and VLBI EOP series for the time interval 
around Dec. 26 and investigate the significance of any discontinuity 
internal to each series.  With respect to a geophysical estimate, Ben Chao 
and Richard Gross have a short article in the 4 Jan 2005 issue of EOS.

I will contact the other services to ask their assessment of their data.

Yours,

Chopo

At 06:34 PM 1/19/2005 +0100, Ron Noomen wrote:

>dear dr. Ma, dear Chopo,
>
>As we all know, the enormous earthquake off the coast of Sumatra on 
>December 26
>last year generated a devastating tsunami with tragic consequences. Whilst
>feeling powerless to have mitigated the effects of this event, it is incumbent
>on the scientific community to make and report observations that may lead to
>greater understanding of such events.
>
>As you know, the ILRS has in place a rapid weekly station coordinate and Earth
>orientation computation program, which provides to the community a combined
>solution from our official and backup combination centres. From this 
>operational
>series we have observed a significant shift in one of the Earth Orientation
>Parameters, in particular the y-component. These results must be reported 
>to the
>community at large, of course. But we think it would strengthen the 
>solution and
>be more appropriate if we were to derive a common result and statement by the
>overall geodetic community, through an inter-technique combination, involving
>IGS, IVS and ILRS. In this case, for obvious reasons, we feel this effort 
>should
>be coordinated by the IERS.
>
>I attach a report of our SLR-based findings, as they are visible in our 
>official
>combination product, which may form the basis of a joint-services paper. I 
>would
>like to request you, the chairman of the IERS, to investigate and 
>stimulate the
>possibility to derive a multi-technique combination observation of the 
>effect of
>the earthquake on geophysical parameters, in this case polar motion and 
>perhaps
>LOD/UT1.
>
>It would be very nice if the findings could be complemented by an 
>interpretation
>by one of our IERS colleagues involved in geophysics/global fluids, like 
>Richard
>Gross. On the other hand, we feel that the publication of this observational
>evidence should not suffer from a fully-detailed geophysical analysis (which
>could very well take quite some time before the final result is out).
>
>We consider that the IERS should coordinate a rapid, joint services 
>publication
>in a journal, such as Nature.
>
>We hope you will give this proposal a serious and timely consideration.
>
>Kind regards,
>
>Ron Noomen
>ILRS Analysis Coordinator
>
>
>