A method of processing seismic data including measurement data and their gradients to obtain gradients of move-out corrected data, comprising deriving gradients of the measurement data, deriving a first term comprising applying a move-out correction function to the measurement data; deriving a second term by applying the move-out correction function to the gradients and deriving gradients of move-out corrected data by adding the first term and the second term. The gradients of move-out corrected data are used to process physical properties of the earth's interior. The method may be used prior to any data processing algorithm which uses measurement gradient data in which move-out correction is applied prior to the algorithm, either because the algorithm makes a zero offset assumption or because it is beneficial for the algorithm to operate on move-out corrected data to reduce aliasing.