SEPARATING CONSTITUENTS IN COMPLEX ANISOTROPIC MEDIA

A structure appears anisotropic when it consists of a fabric that is thinner than the seismic wavelengths that measure it. This fabric can result from periodic thin layering or microcrack orientation. The horizontal layering in sedimentary basins and the oceanic crust generates transverse isotropy, a hexagonal symmetry with a vertical symmetry axis. When observed in plan view, transverse isotropy does not generate a varia.tion of physical properties. However, with the advent of multi-component seismometers and walk-around experiments, azimuthal variations in shear-wave travel times is frequently observed. This anisotropic effect is presumed to result from vertical fractures.