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

[Yingzi Ying]

Dear Dimitri,

Thank you for your reply.

I didn't go deep into the source code.

 From an end-user's opinion, I just would like to input my personal 
source time series at the source positions and get desired outputs from 
the receivers. And I can choose to adopt force source or CMT source from 
the source mechanism flags, as well as output forms.

Big thanks.

Best regards,
Yingzi
On 09/11/2012 05:01 PM, Dimitri Komatitsch wrote:
>
> 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
>>
>>
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>