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Modeling of coupled wave propagation represents a special problem for
certain algorithms. Examining Equation 18 we expect the eigenvalues
of the system to be grouped into two categories for the two propagating wave
types; one in the range of speed of light in the material, the other
in the range of seismic wave speeds. This grouping of eigenvalues
establishes a scale difference between elastic and electromagnetic wavetypes.
This discrepancy poses a problem if we want to propagate both coupled
wavetypes at the same time.
We basically have to propagate the wavetypes with the higher speed on
a grid which is orders of magnitude smaller than the one we use for the
slower speed wavetypes.
Obviously a finite difference algorithm would be costly and inefficient
when propagating the coupled waves on a common space-time grid. A phase shift
related algorithm is much more effective, but is restricted to horizontal
layers. However, in my opinion, a phase shift algorithm
can easily be extended to model or migrate coupled
waves in arbitrary anisotropic media. This is a promising future application.
In this case the disadvantage of being restricted to horizontal layers
is outweighed by the
possibility of calculating coupled material constants using the group theoretical approach of Schoenberg and Muir.

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** Up:** Karrenbach: coupled wave propagation
** Previous:** BOUNDARY CONDITIONS
Stanford Exploration Project

1/13/1998