A small loop frequency-domain electromagnetic (EM) survey is used to map conductivity variations within the earth. SJ Geophysics Ltd. uses APEX Systems MaxMin II or MaxMin 10.
With the MaxMin systems, the primary field is established by sending an alternating current through a coil of wire. The receiver measures both the in-phase and quadrature (out of phase) components of the resultant field. A cable connecting the transmitter and receiver provides a reference signal used to calculate the induced secondary field. MaxMin profiles show the shape, orientation and depth of conductive sources.
Applications
- Locating contaminant plumes and buried metallic objects
- Mapping of lateral and vertical conductivity
- Monitoring groundwater quality at landfills
- Locating steeply dipping bedrock fractures
