[CIG-SEISMO] Simple Asking SPECFEM2D

[Dimitri Komatitsch]

Hi all,

Yes, as in any numerical technique based on time stepping we need to 
shift the source by a constant t0 > 0 in order to have a medium at rest 
when we start the simulation at t = 0; we then subtract that t0 when we 
save the seismograms.

If negative times are a problem for your processing scripts, just edit 
all the ASCII seismogram files and remove all the values for which time 
is negative at the beginning of the file (it is safe to do that).

Best regards,
Dimitri.


On 11/06/2013 01:40 AM, Anton Gulley wrote:
> Hi JungRak
>
> As far as I am aware the source type you will have is a Ricker wavelet.
> It is convenient to have the time start before zero so the peak of the
> Ricker wavelet is at zero.
>
> I am unaware of how to do what you ask using the source_file or Par_file
> other than by editing the source code.
>
> You can always apply a shift in time to your output files
>
>
> Hope this helps
> Anton
>
>
> PhD student at Auckland University
>
>
> On 6 November 2013 13:07, Jungrak SON <jrson2011 at gmail.com
> <mailto:jrson2011 at gmail.com>> wrote:
>
>     Before asking, I appreciate to whom may have tried to develop this
>     great tool.
>
>
>     Hi, I am a beginning master student in Geophysics and please let me
>     ask about SPECFEM2D " *Par_file* ".
>
>     At the line of " *# time step parameters* ", I used to set "
>     *USER_T0 *" as *zero*. This is convenient to use automatically
>     calculated one. However,_may I ask why result  time always starts
>     from *negative value*? what should I do to make the simulation start
>     from zero time?_
>
>     Thanks for your time and concerning. Please * please let me know how
>     to control this.
>
>     Best regards,
>
>     P.S. I am trying to use this tool for near-surface heterogeneous
>     land seismic simulation. :) I trust this amazing SEM tool must be
>     the best method for my research. Thank you.
>
>     - JungRak Son
>
>     Master Student at Texas A&M University
>
>     _______________________________________________
>     CIG-SEISMO mailing list
>     CIG-SEISMO at geodynamics.org <mailto:CIG-SEISMO at geodynamics.org>
>     http://geodynamics.org/cgi-bin/mailman/listinfo/cig-seismo
>
>
>
>
> _______________________________________________
> CIG-SEISMO mailing list
> CIG-SEISMO at geodynamics.org
> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-seismo
>

-- 
Dimitri Komatitsch
CNRS Research Director (DR CNRS), Laboratory of Mechanics and Acoustics,
UPR 7051, Marseille, France    http://komatitsch.free.fr