[CIG-SEISMO] SPECFEM3D - determining the effectiveness of absorbing boundaries

[Shahar Barak]

Hi,

I understand from the references in the manual that the absorbing
boundaries in SPECFEM3D is not perfect. For just using the absorbing
boundaries in the code ( ABSORBING_CONDITIONS Set to .true. to turn on
Clayton-Enquist absorbing boundary conditions ), i.e., without adding
special constraints on the edges such as larger attenuation at the
edges, are there any quantitatively guidelines/suggestions on how far
away should the mesh edges be, given a source type and moment
magnitude?
Also, is the effectiveness of absorbing boundaries scalable? i.e., if
I run tests on a small source within a small volume and find the size
of volume needed in order to eliminate boundary returns, would that
scale by a constant to a larger mesh and a larger source, keeping the
size of mesh elements with respect to the size of the volume the same?
Has anyone done such tests for SPECFEM3D? are there publications?

Thanks,

Shahar Barak
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Crustal Geophysics Research Group
Department of Geophysics, Stanford University
397 Panama Mall, Stanford CA 94305-2215
Mitchell Building, room 463
Office: (650) 725 8229
Cell: (650) 276 6169
shaharb at stanford.edu