[CIG-SEISMO] anti-damping in viscoelastic simulation, it crashes

[Dimitri Komatitsch]

Dear Yingzi,

Unfortunately that is known for being unconditionally unstable 
(mathematically), i.e. impossible; when you amplify the signal you also 
amplify the noise and the scheme quickly blows up.

Best regards,
Dimitri.

On 10/20/2015 03:23 PM, Yingzi Ying wrote:
> Dear Dimitri and All,
>
> I am going to realise a function in viscoelastic simulation with
> SPECFEM2D. I would like to build an anti-damping material, in which the
> wave amplitude can increase rather than decrease during propagation,
> i.e., an inverse process of visco-attenuation. Such processing is
> physically meaningless but might be useful in signal processing.
>
> I added following 3 lines in "compute_forces_viscoelastic.F90"
>
> e1_sum  = -e1_sum
> e11_sum = -e11_sum
> e13_sum = -e13_sum
>
> but the modified code is not stable and crashes.
>
> I have tried to reduce the mesh size and time step, but it still
> crashes(may be not small enough). Should I use double precision instead
> and decrease the amplification factor of the SOURCE?
>
> Do you have any suggestion?
>
> Best regards,
> Yingzi
> _______________________________________________
> CIG-SEISMO mailing list
> CIG-SEISMO at geodynamics.org
> http://lists.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