I'd like to thank Francis Muir for suggesting the idea of using coupled wave propagation in exploration geophysics and for his interesting discussions. Thanks also to Dave Nichols, who always had time to discuss and clarify the complex mathematical description of coupled physical phenomena. Finally I`d like to thank Joe Dellinger for allowing me to use his repertoire of programs for calculating and plotting anisotropic 3D slowness surfaces; without his help none of the figures could have been shown in this paper.