[CIG-SEISMO] simulation of seismic wave propagation excited by a force

[Christina Morency]

Hi Dimitri,

Yes, I can confirm what Yang is saying, it is already in the package,
with interpolation if the source is not located on a GLL point (as it is
indeed done in the 2D btw).

Christina

On 09/11/2012 09:14 AM, Yang Luo wrote:
> I think Daniel (or someone else) has already copied necessary lines from old package.
>
> There is an option "USE_FORCE_POINT_SOURCE" in constant.h, which allows one to use a point force
> (which Yingzi already figured out, or maybe it's already in the manual)
>   logical, parameter :: USE_FORCE_POINT_SOURCE = .false.
>   double precision, parameter :: FACTOR_FORCE_SOURCE = 1.d15
>   integer, parameter :: COMPONENT_FORCE_SOURCE = 3  ! takes direction in comp E/N/Z = 1/2/3
>
> Interpretation is included, if the point force is not located exactly on a GLL point.
>
>
>
>
>
>
> ________________________________________
> From: Dimitri Komatitsch [komatitsch at lma.cnrs-mrs.fr]
> Sent: Tuesday, September 11, 2012 12:01 PM
> To: Yingzi Ying
> Cc: cig-seismo at geodynamics.org; Joseph Charles; Paul Cristini; 谢志南; Yang Luo; Christina Morency
> Subject: Re: [CIG-SEISMO] simulation of seismic wave propagation excited by a   force
>
> Dear Yingzi,
>
> You are right, in the current code there is no option in the Par_file to
> use a point source, but we added this to the todo list right before the
> summer and thus we should/will definitely do it. It is easy to do: just
> add the Ricker wavelet to the accel() vector (which is in fact a force
> vector before we divide it by the mass matrix), to the component you
> want (vertical or horizontal) and you are all set.
>
> Joseph, could you maybe do it? below are a few lines from one of my test
> codes, in which I do just that; let us cut and paste these lines in
> SPECFEM3D (it is just a matter of selecting the right grid point; which
> we already do for a CMT source, thus we could add a force instead of a
> CMT at that location; the only difference being that the CMT source is
> added to all the points of a given spectral element, while a force
> vector should be added to a single point).
>
> Let me talk to Joseph tomorrow to see if we can release a patch of the
> source code soon.
>
> I also cc Yang to see if he has already done that in a local version at
> Princeton maybe (for instance to model a force for some of his oil
> industry simulations in foothill regions?).
>
> Another difficulty is if the location of the force does not correspond
> to a grid point; then there are two options:
>
> - select the closest grid point; i.e. slightly change the location of
> the source (can be done automatically by the code)
>
> - use Christina Morency's way of adding a force source between grid
> points; I think I remember she did that in the 2D code, but I am not
> sure how; thus I cc her.
>
> (that second option would be better, if Christina can confirm that it
> works fine)
>
> Best wishes,
> Dimitri.
>
> ==================================================================
>
> ! ipoinsource is the global grid point at which we add the source
> ! "3" means a vertical force (i.e. we add the force to the vertical
> ! component of the force vector, which is later divided by the mass
> ! matrix to get the acceleration vector)
> ! factor_force is the norm of the force vector to add
> ! ricker(t) is the Ricker wavelet at time t = (it-1)*deltat
>
>    accel(3,ipoinsource) = accel(3,ipoinsource) - factor_force * ricker(t)
>
> ==================================================================
>
> On 09/11/2012 12:59 PM, Yingzi Ying wrote:
>> Hi all,
>>
>> I am trying to use specfem3d to simulate waves excited by a vertical
>> force with user-defined source forms such as ricker wavelet.
>>
>> I tried to do it through adjoint simulation by setting 'SIMULATION_TYPE
>> = 2' and put source position at STATIONS_ADJOINT and receivers at
>> CMTSOLUTION. But I failed.
>>
>> Does anyone have an idea or suggestion how to do active simulations with
>> specfem3d?
>>
>> Thanks in advance.
>>
>> Best regards,
>> Yingzi
>>
>>
>> _______________________________________________
>> CIG-SEISMO mailing list
>> CIG-SEISMO at geodynamics.org
>> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-seismo
> --
> Dimitri Komatitsch - komatitsch aT lma.cnrs-mrs.fr
> CNRS Research Director (DR CNRS), Laboratory of Mechanics and Acoustics,
> UPR 7051, Marseille, France    http://komatitsch.free.fr

-- 
Christina Morency
~~~~~~~~~~~~~~~~~
Geophysicist
Computational Geosciences Group
Atmospheric, Earth and Energy Division
Physical and Life Sciences Directorate
~~~~~~~~~~~~~~~~~
Lawrence Livermore National Laboratory
P.O.Box 808, M/S L-286
Livermore, CA  94551
~~~~~~~~~~~~~~~~~
Office: (925) 422-1686
Email: morency1 at llnl.gov
https://www-pls.llnl.gov/?url=about_pls-scientific_staff-morency_c