[CIG-SEISMO] variable mesh spacing
Dimitri Komatitsch
komatitsch at lma.cnrs-mrs.fr
Fri Mar 25 08:59:56 PDT 2016
Hi Nicholas,
Yes, when there is varying bathymetry i.e. a non-flat ocean bottom,
having a geometrically non-conforming mesh in the horizontal direction
at the ocean bottom interface is difficult to do, one needs to ensure
the conservation of total energy in the numerical scheme along that
interface and that is hard to enforce. There is a really nice recent
paper about this https://hal.inria.fr/hal-01255188 showing that it is
not so easy.
However in the case of a flat interface no such instabilities arise and
the classical SEM can handle that easily; that is not implemented in the
current code but I have a (very) old version from 15 years ago in which
I did that. I still have it somewhere, however it will lack all the
modern features of the current code; if you feel like trying to merge
them I can send it to you.
When doing that ideally one should also use time sub-stepping, which is
also difficult to do properly (see e.g.
http://komatitsch.free.fr/preprints/CMES_time_substepping_2009.pdf ).
Best wishes,
Dimitri.
On 25/03/2016 14:15, Nicholas Mancinelli wrote:
> Hi,
>
> I’m trying to use SPECFEM2D to simulate elastic wave propagation in the crust and lithosphere while including effects from reverberations in the water column. Can you point me to a good method to generate a fine mesh (for the water column) atop a coarser mesh (for the lithosphere)? It does not appear that the built-in (i.e., internal) mesher is capable of generating mesh layers with varying numbers of elements in the x-direction.
>
> Thanks in advance for any advice!
>
> Nick
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--
Dimitri Komatitsch
CNRS Research Director (DR CNRS), Laboratory of Mechanics and Acoustics,
UPR 7051, Marseille, France http://komatitsch.free.fr
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