Systems and methods for identifying sanding in production wells using time-lapse sonic data. Formation anisotropy can be characterized in terms of shear moduli in a vertical wellbore, e.g., vertical shear moduli C44 and C55 in the wellbore axial planes and horizontal shear modulus C66 in the wellbore cross-sectional plane. Changes in formation anisotropy between different times can provide qualitative indicators of the occurrence of sanding in the production well. Before production begins, the horizontal shear modulus C66 is typically less than the vertical shear modulus C44 or C55 or both. At a subsequent time after sanding occurs, the horizontal shear modulus C66 is typically greater than the vertical shear modulus C44 or C55 or both. By comparing the shear moduli of the vertical wellbore at different times, it is possible to identify the occurrence of sanding in the production well using time-lapse sonic data.