Theoretical electromagnetic (EM) responses of a conductive circular cylinder in a conductive half-space are obtained for a frequency range between 10 Hz and 30 kHz. The results show that the spectral characteristics can be used to determine the subsurface configuration of a target body, particularly in terms of its depth. Laboratory experiments using a wide-band sweep-frequency source provide support for the theoretical prediction of the spectral behavior. The experiment employed a harmonic EM source continuously sweeping logarithmically from 4 kHz to 4 MHz over a graphite slab submerged in a conductive solution. The results suggest that a wide-band EM spectral profile displayed in a frequency-distance space may provide many intuitive interpretation schemes which may not be possible with a single or discrete frequency profile.