Frequency-Dependent Anisotropy – Effects of Multi-Fracture Sets on Shear-Wave Polarizations

P264 FREQUENCY-DEPENDENT ANISOTROPY – EFFECTS OF MULTI-FRACTURE SETS ON SHEAR-WAVE POLARIZATIONS 1 Abstract Recently from the analysis of a multi-component VSP for frequency-dependent anisotropy we find that shear-wave anisotropy as inferred from measured time delays between split shear-waves decreases systematically as frequency increases. While in general the polarizations of the fast split shear-waves remain almost constant for deep receivers we notice systematic rotation (up to 20 o ) of polarizations with frequency for shallow receivers. The variation of time-delays with frequency has been successfully interpreted and modelled using a multi-scale rock physics model incorporating aligned fractures in a porous medium