Color display of the localized spectrum

This paper develops a new display technique for seismic cross-sections, called spectral color. The need to visualize frequency information in seismic data is recognized uniformly and often is accomplished through the color display of instantaneous frequency. The spectral content of a reflected event can carry information about the reflecting horizon's characteristics which will not be resolved in the instantaneous state of the record. Spectral color is devised to overcome the problem of displaying an entire localized spectrum at each time sample and offset of a seismic section. The localized spectrum is calculated with a relatively new time-frequency representation called the S-transform, which combines a Fourier technique with adaptive windowing in the frequency domain. A color (RGB triplet) based on the localized spectral content is calculated and the pixel is displayed at the appropriate position in the seismic section. As a result, the seismic cross-section is displayed in an intuitive manner that is much the way we see the world around us. Strongly reflecting or well-lit objects appear to us as bright, and the color tells us about the frequency content of the reflected energy. Spectral color is applied to ultrasonic laboratory data acquired over a thin anisotropic disk. It reveals a change in color (spectral content) with azimuth where no significant amplitude variation with azimuth was observed. Spectral color is illustrated further by application to a 3-D field data set and is compared to other, more standard, color displays.