[CIG-SEISMO] Specfem2D : Small Oscillations in Kernel Data

[Philip Knaute]

Hello again,
and thank you for your quick reply. I suspected the crude way I plot the
Kernels might be the issue. At the moment, I still use the
"TriScatteredInterp()" Matlab command (this uses a Delauney triangulation to
interpolate the scattered Data).
So I had a closer look on the data by fixing the my x coordinate and taking
a 1D line of the Kernel and plotted this data. To do that, I Imported the
Kernel File as Matrix into Matlab and used the "sortrows" command, which
should not mess with the matrix, apart from sorting it.
Then I just extracted (Number of spectral elements in my model * 5) rows
from the Kernel at a certain position and plotted the appropriate collumn
with "plot". That is when I saw the strange zick-zack pattern.

I attached a zip file with pictures of my beta Kernel as a whole (beta.jpg)
and of a vertical line of the kernel data (beta_fixedX.jpg and
beat_fixedX_close.jpg). A picture of my rho (from rho kappa mu) kernel
(rho.jpg) and a closeup (rho-closeup.jpg) to show the checkerboard pattern.
I also attached my .dat, Par_file and SOURCE file.

Thank you very much,
Philip

2011/4/9 Dimitri Komatitsch <dimitri.komatitsch at get.obs-mip.fr>

>
> Dear Philip,
>
> Hopefully Carl Tape, or somebody who is more familiar with the 2D kernel /
> adjoint code than I am, can answer that. Could you maybe email us a few
> screen captures showing pictures of the problem? I think it would help.
>
> Thank you,
> Best regards,
> Dimitri.
>
>
> On 04/08/2011 07:47 PM, Philip Knaute wrote:
>
>> Dear All
>>
>> After getting Specfem2D to run with Scotch (thank you again for your
>> help, Dimitri) I started to work with the sensitivity-kernel function of
>> Specfem2D.
>>
>> But, when I look at my results (e.g. the Kernels) their values seem to
>> oscillate (very small deviations) around an average value.
>>
>> So, if I have a 2D plot of my sensitivity Kernel, I would take a 1D
>> slice for a fixed z value.
>> Looking at that 1D funtcion only depending on the GLL Points in X
>> Direction it would look like a Triangle wave function ( looking
>> something like that /\/\/\/\/\ ).
>> It would oscillate very regularly around an average value, especially at
>> locations where this average value doesn't change.
>> The oscillations seem to be too regular to be noise or an instability of
>> any kind, so I guess it is an intentional feature.
>> Is it an intentional feature of the code and do I have to post process
>> the Kernel-data somehow?
>>
>> Thank you very much for your help.
>> Best regards,
>> Philip
>>
>>
>>
>> _______________________________________________
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>> CIG-SEISMO at geodynamics.org
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>>
>
> --
> Dimitri Komatitsch - dimitri.komatitsch aT get.obs-mip.fr
> Professor, University of Toulouse and Institut universitaire de France,
> CNRS UMR 5563 GET, France   http://www.univ-pau.fr/~dkomati1
>
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