Inversion for Shear-Wave Splitting
A global optimization technique based on a Genetic Algorithm is applied to the problem of inverting shear-wave splitting estimates from an Azimuthal VSP experiment recorded at the Conoco Borehole Test Facility, Oklahoma. The optimal model derived from the inversion is in excellent agreement with a-priori measurements. The inversion results indicate that the shear-wave splitting observations can be interpreted in terms of a dipping fracture set or an orthorhombic structure constructed from a vertical fracture set embedded in a equivalent anisotropic fine layering medium. Resolution of this non-uniqueness cannot be achieved with the available data, however with an appropriate acquisition geometry these two solutions may be differentiated.