[CIG-SEISMO] single force solution

[Sevan Adourian]

Hi cig-seismo community,

I'm trying to compute Green's functions using Specfem3D-Globe, using a
single force point source solution coupled with a source time function that
basically represents a filtered Dirac delta. In order to test my
implementation, I imposed a source at a point A and looked at the obtained
Green's function at a receiver B. Then, I switched the position of the
source and the receiver and compared the 2 in order to check the
reciprocity of those Green's functions.

It turned out that I have a perfect reciprocity (in the frequency band that
correspond to my filtered Dirac delta) only on the component in which I
input the force, while the other components don't quite match.

I strongly suspected a reference frame rotation issue, so I tried to input
the force in the global xyz coordinate system (i.e. adding the force
directly in the accel_crust_mantle array in the comp_add_sources
subroutine, without multiplying with the nu_source matrix) and looked at
the Green's functions in this xyz coordinates system (ie, directly writing
in the seismograms structure the values of ux, uy and uz computed in the
compute_seismogram subroutine), but I still have this issue. Would anyone
have an idea of where this probable rotation issue could come from?

I'm working on specfem3D-Globe v6.0.0.

Thanks in advance for your help!
Sévan

-- 
Sevan Adourian
Masters Student at Ecole Normale Superieure de Paris
sevan.adourian at ens.fr
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