1. A method to determine a radial profile of shear parameters for a formation including a cased borehole, the method comprising: determining a fractional variation of a first shear modulus at a first radial position from the borehole based on a first weighted average of fractional variations of Stoneley wave velocities for different wavenumbers, the first weighted average being based on first weights determined using a perturbation model including parameters to model the borehole casing; and determining fractional variations of second and third shear moduli at respective second and third radial positions from the borehole based on second and third weighted averages of fractional variations of respective first and second flexural wave velocities for different wavenumbers, the first and second flexural wave velocities associated with respective first and second orthogonal borehole axial planes of the formation, the second and third weighted averages being based on respective second and third weights determined using the perturbation model.