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

[Yingzi Ying]

Hi Christina,

If you are going to do this, the inputs maybe go into an active array
rather than a single source.

Best,
Yingzi
On 09/11/2012 05:53 PM, Christina Morency wrote:
> Hi Yingzi,
> 
> At the moment all the source time functions (Gaussian, Ricker,
> Heaviside) are defined in comp_source_time_function.f90 which is located
> in src/specfem3D.
> Then, the proper function name needs to be specified in
> compute_add_sources_*****.f90
> 
> I guess we could design a way to read an external file for the source
> time function if USE_FORCE_POINT_SOURCE is on, but I don't know how much
> of a priority this is for the main developers - Dimitri would be the one
> to tell.
> Or we could have a single source name [comp_source_time_function]
> associated to the source for USE_FORCE_POINT_SOURCE, and users could
> then implement their own source in comp_source_time_function.f90
> (basically a line), without having to change names in
> compute_add_sources_*****.f90 ? Any thoughts ?
> 
> Christina
> 
> On 09/11/2012 09:41 AM, Yingzi Ying wrote:
>> Hi Christina,
>>
>> Can you also add a feature to use user-defined source form inputted from
>> a file.
>>
>> Best,
>> Yingzi
>> On 09/11/2012 05:34 PM, Dimitri Komatitsch wrote:
>>> Hi Christina and Yang, Hi all,
>>>
>>> OK, great. This is excellent news.
>>>
>>> So let us just move this "USE_FORCE_POINT_SOURCE" flag from
>>> setup/constants.h.in to DATA/Par_file, and let us mention it in the manual.
>>>
>>> Jo, could you please do that and commit the changes?
>>>
>>> Thank you,
>>> Dimitri.
>>>
>>> On 09/11/2012 06:17 PM, Christina Morency wrote:
>>>> 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
>