f Pore fluid effects on seismic velocity anisotropy

Most crustal rocks are found experimentally to be seismically anisotropic, due to microstructural fabric, fine scale layering, and aligned microcracks. The crack effects have been emphasized most, because of their sensitivity to stress, and their impact on permeability. In spite of this emphasis on cracks it is surprising that few experimental (eg., Lucet and Tarif, 1988 ; Zamora and Poirier, 1990) and theoretical (eg ., Brown and Korringa, 1975; Hudson, 1991) studies exist on the critical anisotropic effects of pore fluids, pore pressure, and frequency. We find that it can be misleading to interpret seismic anisotropy without a complete understanding of these effects in aniso tropic cracked media. This is particularly true when coupled with an intrinsically anisotropic mineral matrix .