sfspectra computes spectrum, the absolute value of the 1-D Fourier transform along the fast axis.
The following example from rsf/su/rsfkasper shows a seismic shot gather before and after high-pass filtering and the corresponding spectra computed with sfspectra.
sfspectra has only one option: all=. If all=n (the default behavior), the spectrum is computed separately for each trace. If all=y, the output is the spectrum averaged across all traces.
and the corresponding 2-D spectra computed with sfspectra2