1. A method to determine a radial profile of shear parameters for a formation including a cased borehole, the method comprising: measuring Stoneley waveforms and dipole sonic waveforms in the cased borehole by a sonic tool; 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; 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; determining a radial profile of the first shear modulus at a set of radial positions from the borehole in a borehole cross-sectional plane of the formation based on fractional variations of the first shear modulus determined at the respective set of radial positions from the borehole; determining respective radial profiles of the second and third shear moduli at respective second and third sets of radial positions from the borehole in the respective first and second orthogonal borehole axial planes of the formation based on respective fractional variations of the second and third shear moduli determined at the respective second and third sets of radial positions from the borehole; determining respective radial profiles of the shear slownesses at the respective second and third sets of radial positions from the borehole in the respective first and second orthogonal borehole axial planes of the formation based on the respective radial profiles of the second and third shear moduli; and determining the radial profile of the shear parameters for the formation including the cased borehole; wherein the shear parameters comprise the shear moduli and the shear slowness.