[CIG-SEISMO] time reversed computation in specfem2d

[Dimitri Komatitsch]

Hi Christina,

No problem at all, doing it in the next few weeks or months
is fine! Jörg can probably help for the tests since he had planned to 
develop an adjoint code from scratch anyway. Running a few tests with an 
existing code will be much faster.

Thanks,
Dimitri.

Chris Morency wrote:
> Hello Dimitri,
> 
> I feel it is actually my bad ! As you know, we had discussed the merging 
> of the 2D version we have been developing including poroelasticity. This 
> version does have the adjoint capabilities for acoustic, elastic, and 
> poroelastic media. It is still on a branch....
> I am finishing dealing with some domain decomposition issues when using 
> irregular (CUBIT generated) meshes. It shouldn't be too long and then I 
> should be able to fully merge this new version in place of the present 
> specfem2D.
> Really sorry about that. I am presently working on it.
> 
> Christina
> 
> Dimitri Komatitsch wrote:
>>
>> Dear Jörg and Carl,
>>
>> This has been done already, by Carl Tape et al. from Caltech (USA).
>> See for instance their papers below and in PDF at 
>> http://www.gps.caltech.edu/~carltape/research/CV.html#Pubs
>>
>> I thought the kernel capability and adjoint runs had been added to 
>> SPECFEM2D already (on the SVN server). Carl, did you do it?
>> We talked about it (merging your kernels in the SVN code) two years ago
>> and I thought that it had been done since then. If not, would it be 
>> easy to do? It would clearly be very useful. As always, working on a 
>> local version not under SVN control was a bad idea to begin with... 
>> because now it is a dead branch... could somebody (maybe Jörg) cut and 
>> paste your adjoint routines in the SVN code? (if you sent him a copy 
>> of your old 2D code)
>>
>> In the future let us all use SVN all the time from the beginning of 
>> any new SPECFEM project.
>>
>> Thanks,
>> Cheers,
>>
>> Dimitri.
>>
>> Tape, C., Liu, Q., and J. Tromp, 2007, Finite-frequency tomography 
>> using adjoint methods---Methodology and examples using membrane 
>> surface waves,  Geophysical Journal International, v. 168, 1105-1129.
>>
>>
>> Tromp, J., Tape, C., and Q. Liu, 2005, Seismic tomography, adjoint 
>> methods, time reversal, and banana-doughnut kernels, Geophysical 
>> Journal International, v. 160, p. 195-216.
>>
>>
>> pge05bqw at studserv.uni-leipzig.de wrote:
>>> Hello,
>>> i'am trying to add a time reversed computation to specfem2d. First I  
>>> thought it would be enough to change sign of deltat(and 
>>> deltatcube...)  after some time iteration steps(e.g. half of NSTEP). 
>>> But it doesn't  seem to be that easy, because it leads to a extremly 
>>> big maximum norm  of vector field, which aborts the program.
>>> Does anyone have an idea how this could work?
>>> Thanks,
>>> Jörg Buchwald
>>> Student
>>> University of Leipzig
>>>
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>>
> 

-- 
Dimitri Komatitsch - dimitri.komatitsch aT univ-pau.fr
Professor, University of Pau, Institut universitaire de France,
CNRS and INRIA Magique3D, France   http://www.univ-pau.fr/~dkomati1