Frequency Domain EM

Frequency Domain Electro Magnetic (FDEM) induction involves generating electromagnetic fields which induce currents in the earth which in turn cause the subsurface to create secondary magnetic fields. By measuring the magnetic fields, subsurface properties and features can be deduced. This method measures the magnitude and the phase of the induced currents, which are related to the subsurface electrical conductivity. Electrical conductivity is a function of the soil and rock matrix, percentage of saturation, and the conductivity of the pore fluids. FDEM instruments provide two measurements simultaneously; the electrical conductivity data and the in-phase component, which responds to magnetic susceptibility and metal.

In certain cases, depths of up to 50 meters can be mapped.

FDEM Applications:

Mineral Exploration:

• Detect dyke type orebodies
• Detect lens type orebodies
• Detect shallow conductors (up to 50 meters in some environments)

Water Resources:

• Locate conductive faults in fractured aquafers
• Asses water table characteristics
• Characterize salt water wedge extensions in ground water 

Environment:

• Monitor ground pollution
• Detect leaks and monitor degradation in waste disposal
• Locate and manage buried structures

Natural Hazards:

• Detect and characterize cavities
• Assess landslide extension and volume
• Detect and locate clay layers for geotechnical applications

FDEM Instruments:

IES uses Iris Instruments PROMIS 10.  The PROMIC 10 instrument is a multi-frequency, multi-spacing 3 component slingram type EM System for sounding and profiling. 

FDEM Software and Data Processing:

IES uses a combination of proprietary software and Iris Instruments Emsys software to process FDEM data.