[CIG-SEISMO] single force solution
Sevan Adourian
sevan.adourian at berkeley.edu
Wed Apr 12 06:26:46 PDT 2017
Hi Dimitri,
Thanks for your answer! Yes, I'm continuing Yder's work on box tomography,
and I'm trying to allow the stations to be outside of the box (which is why
I need to compute the Green's functions from an "outside" receiver to each
point of the mirror for a later convolution with the wavefield). In my case
I need to couple SPECFEM with a slightly modified RegSEM.
But reading what you describe, the problem might still come from me because
the issues I'm facing are on the SPECFEM side only. So if you tell me it
already worked, I might still do something wrong.
Regards,
Sévan
On Wed, Apr 12, 2017 at 3:10 PM, Dimitri Komatitsch <
komatitsch at lma.cnrs-mrs.fr> wrote:
>
> Hi Sevan,
>
> Yes, in earlier work (http://komatitsch.free.fr/pre
> prints/GJI2_Vadim_2015.pdf and http://komatitsch.free.fr/prep
> rints/Geology_Chevrot_2016.pdf) we have coupled SPECFEM3D with DSM and
> that worked fine, however more recently we have tried to couple SPECFEM3D
> with AxiSEM to do FWI locally with our wavefield injection technique (also
> similar to e.g. Masson and Romanowicz's box tomography approach) and so far
> we get some weird extra phases, possibly something we are doing wrong in
> some rotations. Not sure if the problem is the same as yours, it could also
> be a small mistake we made in the representation theorem coupling integral
> or something like that.
>
> Since you are at Berkeley, is this related to what Yder was doing? (I
> think he was using finite differences, not SPECFEM?).
>
> Thanks,
> Best wishes,
>
> Dimitri.
>
> On 04/12/2017 03:01 PM, Sevan Adourian wrote:
>
>> Hi Hom Nath and Dimitri,
>>
>> Alright then, I'll be waiting for the tests of your new version then!
>> Dimitri, may I ask you which problems you have faced in the Green's
>> functions computation you mentioned earlier? Do you also have one
>> component that is satisfying reciprocity? I'm asking because I'm trying
>> to couple specfem with another external code as well.
>>
>> Thanks and regards,
>> Sévan
>>
>> On Wed, Apr 12, 2017 at 1:51 PM, Hom Nath Gharti <hgharti at princeton.edu
>> <mailto:hgharti at princeton.edu>> wrote:
>>
>> Hi Sévan,
>>
>> New implementation is very similar, but the source time function
>> will have several options. I make it more general because some
>> people were interested on a moving source with sine source time
>> function, for exampme.
>>
>> Best,
>> Hom Nath
>>
>>
>> On Wed, Apr 12, 2017, 7:36 AM Sevan Adourian
>> <sevan.adourian at berkeley.edu <mailto:sevan.adourian at berkeley.edu>>
>> wrote:
>>
>> Hi Hom Nath and Dimitri,
>>
>> Thank you Dimitri and Hom Nath for the feedback. Hom Nath, will
>> your new implementation be on the model of what's done in
>> specfem Cartesian (i.e. with the FORCESOLUTION file), and will
>> it support a source that is not on a node of an element without
>> relocating this source? And will it still use a ricker as a
>> source time function?
>>
>> Thanks,
>> Sévan
>>
>>
>> On Wed, Apr 12, 2017 at 1:24 PM, Hom Nath Gharti
>> <hgharti at princeton.edu <mailto:hgharti at princeton.edu>> wrote:
>>
>> Hi Dimitri,
>>
>> I will commit!
>>
>> Best,
>> Hom Nath
>>
>> On Wed, Apr 12, 2017, 7:09 AM Dimitri Komatitsch
>> <komatitsch at lma.cnrs-mrs.fr
>> <mailto:komatitsch at lma.cnrs-mrs.fr>> wrote:
>>
>>
>> Hi Hom Nath,
>>
>> Perfect, thanks!
>> Then please remember to commit it to GitHub.
>>
>> Best regards,
>> Dimitri.
>>
>> On 04/12/2017 01:06 PM, Hom Nath Gharti wrote:
>> > Hi Sévan,
>> >
>> > I am about to finish new point force implementation. I
>> will let you know
>> > once it is ready for testing.
>> >
>> > Best,
>> > Hom Nath
>> >
>> > On Wed, Apr 12, 2017 at 6:36 AM, Dimitri Komatitsch
>> > <komatitsch at lma.cnrs-mrs.fr
>> <mailto:komatitsch at lma.cnrs-mrs.fr>
>> <mailto:komatitsch at lma.cnrs-mrs.fr
>>
>> <mailto:komatitsch at lma.cnrs-mrs.fr>>> wrote:
>> >
>> >
>> > Hi Sevan,
>> >
>> > I guess you can keep cc'ing the list because it is
>> an issue Clément,
>> > Vadim, Paul, Sébastien and I have been facing as
>> well in our coupling
>> > with external codes, thus we are interested in
>> knowing more about the
>> > potential problem.
>> >
>> > Thanks,
>> > Best wishes,
>> > Dimitri.
>> >
>> > On 04/12/2017 11:24 AM, Sevan Adourian wrote:
>> > > Hi Hom Nath,
>> > >
>> > > Thanks for your answer and concern. Since you
>> suggest something that is
>> > > not directly "specfem related", can I send you
>> directly an email so that
>> > > we can discuss it? And then I can post the
>> solution once we'll find it,
>> > > in order to close the topic!
>> > >
>> > > Thanks again,
>> > > Sévan
>> > >
>> > > On Tue, Apr 11, 2017 at 8:46 PM, Hom Nath Gharti <
>> hgharti at princeton.edu <mailto:hgharti at princeton.edu>
>> <mailto:hgharti at princeton.edu
>> <mailto:hgharti at princeton.edu>>
>> > > <mailto:hgharti at princeton.edu <mailto:
>> hgharti at princeton.edu>
>> <mailto:hgharti at princeton.edu
>> <mailto:hgharti at princeton.edu>>>> wrote:
>> > >
>> > > Hi Sévan,
>> > >
>> > > Do you also switch the orientations of source
>> and receiver?
>> > >
>> > > Thanks,
>> > > Hom Nath
>> > >
>> > > On Tue, Apr 11, 2017 at 1:39 PM, Sevan
>> Adourian
>> > > <sevan.adourian at berkeley.edu
>> <mailto:sevan.adourian at berkeley.edu>
>> > <mailto:sevan.adourian at berkeley.edu
>> <mailto:sevan.adourian at berkeley.edu>>
>> > <mailto:sevan.adourian at berkeley.edu
>> <mailto:sevan.adourian at berkeley.edu>
>>
>> > <mailto:sevan.adourian at berkeley.edu
>> <mailto:sevan.adourian at berkeley.edu>>>>
>> > > wrote:
>> > >
>> > > Hi cig-seismo community,
>> > >
>> > > I'm trying to compute Green's functions
>> using Specfem3D-Globe,
>> > > using a single force point source
>> solution coupled with a
>> > source
>> > > time function that basically represents
>> a filtered Dirac
>> > delta.
>> > > In order to test my implementation, I
>> imposed a source at a
>> > > point A and looked at the obtained
>> Green's function at a
>> > > receiver B. Then, I switched the
>> position of the source
>> > and the
>> > > receiver and compared the 2 in order to
>> check the
>> > reciprocity of
>> > > those Green's functions.
>> > >
>> > > It turned out that I have a perfect
>> reciprocity (in the
>> > > frequency band that correspond to my
>> filtered Dirac delta)
>> > only
>> > > on the component in which I input the
>> force, while the other
>> > > components don't quite match.
>> > >
>> > > I strongly suspected a reference frame
>> rotation issue, so I
>> > > tried to input the force in the global
>> xyz coordinate system
>> > > (i.e. adding the force directly in the
>> accel_crust_mantle
>> > array
>> > > in the comp_add_sources subroutine,
>> without multiplying
>> > with the
>> > > nu_source matrix) and looked at the
>> Green's functions in this
>> > > xyz coordinates system (ie, directly
>> writing in the
>> > seismograms
>> > > structure the values of ux, uy and uz
>> computed in the
>> > > compute_seismogram subroutine), but I
>> still have this issue.
>> > > Would anyone have an idea of where this
>> probable rotation
>> > issue
>> > > could come from?
>> > >
>> > > I'm working on specfem3D-Globe v6.0.0.
>> > >
>> > > Thanks in advance for your help!
>> > > Sévan
>> > >
>> > > --
>> > > Sevan Adourian
>> > > Masters Student at Ecole Normale
>> Superieure de Paris
>> > > sevan.adourian at ens.fr
>> <mailto:sevan.adourian at ens.fr>
>> <mailto:sevan.adourian at ens.fr
>> <mailto:sevan.adourian at ens.fr>>
>> > <mailto:sevan.adourian at ens.fr
>> <mailto:sevan.adourian at ens.fr>
>> <mailto:sevan.adourian at ens.fr
>> <mailto:sevan.adourian at ens.fr>>>
>> > >
>> > >
>> > >
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>> > >
>> > >
>> > >
>> > >
>> > > --
>> > > Sevan Adourian
>> > > Masters Student at Ecole Normale Superieure de
>> Paris
>> > > sevan.adourian at ens.fr <mailto:
>> sevan.adourian at ens.fr>
>> <mailto:sevan.adourian at ens.fr
>> <mailto:sevan.adourian at ens.fr>>
>> > <mailto:sevan.adourian at ens.fr
>> <mailto:sevan.adourian at ens.fr>
>> <mailto:sevan.adourian at ens.fr
>> <mailto:sevan.adourian at ens.fr>>>
>> > >
>> > >
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>> >
>> > --
>> > Dimitri Komatitsch, CNRS Research Director (DR CNRS)
>> > Laboratory of Mechanics and Acoustics, Marseille,
>> France
>> > http://komatitsch.free.fr
>> > _______________________________________________
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>>
>> --
>> Dimitri Komatitsch, CNRS Research Director (DR CNRS)
>> Laboratory of Mechanics and Acoustics, Marseille, France
>> http://komatitsch.free.fr
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>>
>>
>> --
>> Sevan Adourian
>> Masters Student at Ecole Normale Superieure de Paris
>> sevan.adourian at ens.fr <mailto:sevan.adourian at ens.fr>
>>
>>
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>>
>>
>>
>> --
>> Sevan Adourian
>> Masters Student at Ecole Normale Superieure de Paris
>> sevan.adourian at ens.fr <mailto:sevan.adourian at ens.fr>
>>
>>
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>>
> --
> Dimitri Komatitsch, CNRS Research Director (DR CNRS)
> Laboratory of Mechanics and Acoustics, Marseille, France
> http://komatitsch.free.fr
> _______________________________________________
> CIG-SEISMO mailing list
> CIG-SEISMO at geodynamics.org
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-seismo
>
--
Sevan Adourian
Masters Student at Ecole Normale Superieure de Paris
sevan.adourian at ens.fr
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