[CIG-SEISMO] suspicious bug of the gravity calculations

[Dimitri Komatitsch]

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