Dictionary:Anisotropy, weak

Seismic velocities in anisotropic media are initially derived as functions of the elastic moduli. But they may be re-formulated in terms of two reference velocities, plus several (many?) non-dimensional combinations of the moduli. If these combinations reduce to zero in the degenerate case of isostropy, they may be called anisotropic parameters. There are several ways to do this .

In the case of weak anisotropy, those relevant to a particular problem (e.g. P-wave reflections) are all much less than 1.