Seismic data processing is a step for correcting all earth propagation effects in order to get an accurate seismic image of the subsurface. During this step, the signal is enhanced and the noise is removed. Many seismic data processing steps are more conveniently carried out in the frequency domain. Therefore we shall start the seismic processing chapter with a discussion on the Fourier transform. © 2022 Elsevier Inc. All rights reserved.