Cubit meshing with PML absorbing boundaries

[ARBolton96]

Hi Devs,

I'm having difficulty following the present examples that use C-PML absorbing boundaries for generated Cubit meshes and was hoping for some guidance.

Looking at the PDF PML_CUBIT_notes_from_Emanuele_Casarotti_16oct2012.pdf in the EXAMPLES/applications/CPML_examples/CPML_realistic_mesh_with_topography/ directory, it looks to me as though the PMLs are explicitly meshed through Cubit, which can be (apparently) confirmed by opening the test_cpml_2layer.cub file in Cubit (shown below).

This explicit PML definition would be my preferred method to create absorbing boundaries, since I can more readily identify problems in my mesh generation.

However, this example does not provide information to the user as to how the Cubit mesh was converted to the SPECFEM3D ASCII mesh file format. Moreover, all other examples in the CPML_examples/ directory use the CUBIT_GEOCUBIT Python library. As far as I can tell from these examples, the user can either explicitly define blocks for the materials using Cubit: e.g.,

block 1 hex in vol 1
block 1 name "elastic"
block 1001 face in surface 25 41 43 61 63 69 75 79 86
block 1001 name "face_topo"
...
{do the same for face_abs_xmin, xmax, ymin, ymax, and bottom}

or the user can define these blocks implicitly by calling geocubitlib.boundary_definition.define_bc() - a la the CPML_examples/. The last step in the block_mesh-anisotropic.py examples therein use geocubitlib.cubit2specfem3d.export2SPECFEM3D('MESH') to generate the SPECFEM3D mesh files. HOWEVER, none of these Python files specify the cpml=True the function export2SPECFEM3D(), which (as far as I can tell) is required to create PML boundaries from the given mesh.

Is there any guidance for creating SPECFEM3D meshes in Cubit with PMLs outside of these examples? Is there anything obvious I'm missing in my search through the examples?

Thanks!