Figure 4. Seismic frequency (vertical axis) and wavelength (horizontal axis) information embedded in the data window labeled Transform window on Figure 3. This data analysis shows that if production seismic data are acquired at this test site with a 220-foot receiver array (Figure 3), the frequency bandwidth should span approximately 80 Hz and each field record should be dominated by high-velocity reflection signals (events labeled Reflector 1 and Reflector 2). The format used to exhibit this frequency-wavelength information on a black/white printer shows how geophysicists had to display data analyses in the field in olden days before color plotters were field portable.