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Coupled wave propagation in a solid body is possible to describe using a
unified formulation inferred from general principles.
In this paper coupling between elastic and
electromagnetic and thermal quantities is derived as an example; other quantities describing the dynamic state of a solid body, such as magnetic fields, can
easily be included.
Since fluid flow is excluded, the theory is completely linear. Using coupled conservative and constitutive equations coupled wave equations can be formulated in the time domain.
Transforming in the Fourier domain leads to an eigenvalue problem, the
generalized Christoffel equation. By solving this equation, wave speeds and
particle motions of waves traveling in the medium can be calculated.
As we see from the examples of quartz and Lead-Titanate-Zirconate, 3D slowness surface plots show significant difference in uncoupled and coupled
wave propagation behavior.
The fact, that boundary conditions give a
major effect on
coupled wave propagation needs careful consideration, and
suggests that coupling phenomena can be observed not only,
when measuring all coupled
quantities, but also when boundary conditions are specified such that one
coupled quantity is eliminated. Such a hidden variable still produces
a significant coupling phenomena. This suggests that coupling phenomena could
prove to be significant in potential geophysical
applications such as enhanced
oil recovery and detailed studies of hydrocarbonceous target zones.

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** Up:** Karrenbach: coupled wave propagation
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Stanford Exploration Project

1/13/1998