The reflectivity of any isotropic elastic property can be expressed as a sum of velocity and density reflectivities. So too can the standard AVO parameters, intercept, gradient and curvature. This allows elastic property reflectivities to be expressed as sums of AVO parameters. By approximating the curvature term where necessary elastic property reflectivities are shown to be vectors in AVO intercept-gradient (AB) space, the vector angles and lengths having a small dependence on Vp/Vs ratio. By using pairs of normalized elastic property reflectivities as basis vectors the position of reflectivity points in AB space may be directly determined from elastic property contrasts. This gives more intuitive insight to the structure of intercept-gradient crossplots. Expressions for the impedance equivalent of any reflectivity expression, such as elastic or extended elastic impedance, can be directly derived from the standardised reflectivity expression.


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