Geophysicists in the seismic exploration industry have long recognized the potential benefits of extending the bandwidth of seismic measurements to well below 10 Hz. Low frequencies generated by a seismic shot travel much farther through the subsurface than do higher frequencies, just as the low frequencies in thunder travel farther in the atmosphere. Thus, the amount of power available in the low end of the seismic spectrum is especially important for deep exploration targets, such as subsalt and sub-basalt plays, and for deep crustal studies. In many areas of the world higher frequencies are often too attenuated, scattered, and dispersed to provide useful signal for probing such objectives. Also, low frequencies play a critical role in the inversion process by which seismic data are converted into acoustic impedance sections and ultimately into reservoir properties. Surface seismic data usually lack low frequencies necessary for accurate inversion, so they are commonly augmented by data from well-log measurements as part of the inversion process. When well-log data are sparse or not available, inversion of seismic data is problematic.