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

[Yingzi Ying]

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