[CIG-SEISMO] 回复: Fwd: RE: suspicious bug of the gravity calculations

[赵明]

Hi Dimitri,Roland,
Thank you very much for your reply and suggestion. the observation can't be at the surface of the model,I tried once again for two depths of the observations plane:z=-10m and z=-122 m. The -122m seems to be quite normal(toto_minus_122.ps), while z=-10m have abnormal values at the down left corner.
Cheers
Ming--------- 原始邮件信息 ---------
发件人: "Dimitri Komatitsch" <komatitsch at lma.cnrs-mrs.fr>
收件人: <mzhao at cea-igp.ac.cn>, "Roland Martin" <roland.martin at get.omp.eu>
主题: Fwd: RE:[CIG-SEISMO] suspicious bug of the gravity calculations
日期: 2017/06/03 23:46:11 (Sat)

Hi Ming,

I am forwarding you this email from Roland, because when he sends it to 
you from his account he gets an error message.

Roland, attached is the file toto.ps

Cheers,
Dimitri.

-------- Forwarded Message --------
Subject: RE:[CIG-SEISMO] suspicious bug of the gravity calculations
Date: Sat, 3 Jun 2017 14:21:15 +0000
From: MARTIN Roland <Roland.MARTIN at Get.omp.eu>
To: Dimitri Komatitsch <komatitsch at lma.cnrs-mrs.fr>, 赵明 
<mzhao at cea-igp.ac.cn>

Hi Ming,

It is not possible to put obsevation points on the topography solution 
will become usntable there.
THis version is in revision and we need to work a little bit more on it 
before the release. I can not see the toto.ps because I did nit receive it.

Cheers
Roland
________________________________________
De : Dimitri Komatitsch [komatitsch at lma.cnrs-mrs.fr]
Envoyé : samedi 3 juin 2017 16:09
À : 赵明; cig-seismo at geodynamics.org; 赵明; MARTIN Roland; CHEVROT 
Sebastien; Vadim Monteiller
Objet : Re: [CIG-SEISMO] suspicious bug of the gravity calculations

Dear Ming, dear all,

Thanks! Let me cc Roland Martin, who is the expert on that.
However, it seems you used an observation surface that is located in z =
0 i.e. at elevation zero, but the gravity formulas are undefined there
(they involve a term with 1/r , in which r is the distance to the
surface). Thus, could you try again using a non-zero elevation?
everything should work fine then.

Also, I think the results should be symmetric, but not necessarily
identical at all points (since the mesh has a finite size, you should
see different values near the edges than in the center, in a symmetric
fashion (I think, but I am not an expert; Roland will confirm).

Thanks,
Cheers,

Dimitri.

On 06/03/2017 02:05 PM, 赵明 wrote:
> Hi Everyone,
>
> I tried the gravity field calculation of SPECFEM3D using the given
> example:
> homogeneous_halfspace_HEX8_elastic_absorbing_Stacey_5sides.However,I
> found the results seem to be abnormal at some observations.
>
> Since it is a homogenous model,the gravity value should be the same to
> the observation on the surface.However,look at the toto.ps,there are
> some place (very likely to be the boundary of some elements) the gravity
> is abnormal.
>
> Best regards
> Ming Zhao
>
>
>
>
> _______________________________________________
> CIG-SEISMO mailing list
> CIG-SEISMO at geodynamics.org
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-seismo
>

--
Dimitri Komatitsch, CNRS Research Director (DR CNRS)
Laboratory of Mechanics and Acoustics, Marseille, France
http://komatitsch.free.fr

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