We explore the potential of multi-angle AVO inversion of P-P and P-S reflections from a fracture to estimate fracture properties. Although AVO analysis of welded interface like geological layer boundaries is common, the use of AVO variations for nonwelded boundaries like fractures is yet to be investigated. We conduct laboratory experiments to measure reflection responses of dry and wet fractures. The observed P-P reflections of the fracture and the fracture aperture are very well predicted by the nonwelded interface model. We invert the angle-dependent P-P reflectivity of the fracture to estimate both normal and tangential fracture compliances. The estimated value of the normal compliance is accurate, and it is also possible to obtain the value of the non-zero tangential compliance. We find that supplementing the information of converted P-S reflections in the AVO inversion greatly improves the estimate of the tangential compliance. The calculated compliance ratio clearly shows the existence of fluid in the fracture. This finding can be crucial for new applications in a wide range of scale - from earthquake seismology, deep and shallow seismic exploration, to nondestructive material testing.
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