VLF

Very Low Frequency (VLF) Surveys

VLF surveys can locate water-bearing fractures to assist in monitor well installation for remedial investigations. This method is particularly well suited for fractures in crystalline rocks.

VLF is commonly conducted using a VLF meter, which uses EM fields to locate fractures. The VLF meter uses the magnetic components of the electromagnetic field generated by long-distance radio transmitters in the VLF band, the transmitters are used for long-distance communication between Naval stations. The frequencies operated during the survey could be set on Naval stations such as the Annapolis, Maryland and Cutler, Maine stations. Conductive structures in the subsurface locally affect the direction and strength of the field generated by the transmitted radio signal. The VLF meter measures radio signal distortion and presents the result directly on the display screen.