A major aspect of seismic research and seismic processing is related to operations which are based on mathematical transform methods. In particular, much of seismic processing would not exist without numerical Fourier transforms. Filtering is a related subject, because the majority of filters are applied in the frequency domain, or are at least representable mathematically as frequency domain operations.
In addition to standard Fourier transforms, there are a couple of other transforms, such as the Hilbert transform, and the Gabor transform which are also included in the SU package. These items may find more use as educational tools, rather than processing tools.