Dear all,
I am facing a problem when I use the code : “xconvert_external_layers_of_a_given_mesh_to_CPML_layers” whith a free surface at the top of the model.
The code generates a " free_or_absorbing_surface_file_zmax" file which contains only “0” as a value.
And then when I try to execute the specfem3d code, it generates the error " wrong or empty definition of upper surface of the mesh in file free_or_absorbing_surface_file_zmax"
Can anyone help me with that please ?
Thanks a lot 
Stay safe.