Ground-based geophysical experiments were undertaken to test the possibility of de-
tecting groundwater using nuclear magnetic resonance from an airborne electromagnetic
prospecting system. Two experimental surveys were conducted: One over an ice-covered
lake, containing a large volume of freshwater, and the other over an equal volume of
land, with little to no freshwater in the subsurface. If exposed to a radio-frequency pulse
at the Larmor frequency, protons in water molecules create a magnetic eld oscillating
at the Larmor frequency. Both surveys used a 120-second long frequency sweep from
2300 to 2400 Hz. It was initially hypothesized that as the frequency passed over the
Larmor frequency, 2348 Hz, there would be phase shift between the transmitter and
receiver signals. Phase measurements, using the heterodyne method, between the lake
and land data proved to be inconclusive, although the lake data showed an oscillatory
decay in the o -time, not equal to the Larmor frequency.
