Our low-frequency testing methods get high marks when it comes to locating underground resources.
A VLF survey uses the magnetic components of the electromagnetic field generated by existing radio transmitters broadcasting in the VLF (10-30 kHz) band. These transmitters are used for long-distance military communication throughout the world. Conductive bodies such as water-bearing fractures, buried metal pipes and certain ore bodies affect the direction and strength of the field generated by the transmitted radio signal, producing large secondary electromagnetic and magnetic responses that enable targets to be located at depths up to 100 feet. Features such as fractures or faults should strike toward a transmitting station so that the receiving antenna is oriented perpendicular to the potential targets, maximizing signal strength.