Skip to main content
Contact Us

Electromagnetic (EM)

The electromagnetic field consists of the combination of the electric field and the magnetic field and is generated locally by any distribution of electric charge and electric current varying over time, propagating in the form of electromagnetic waves. Electromagnetic (EM) methods include various techniques, survey methods, applications, and interpretation procedures. Each technique, however, involves the measurement of one or more electric or magnetic field components by an “EM receiver,” from some natural or artificial source of electromagnetic energy—the “EM transmitter.”

EM tools are used to measure the Earth’s response to natural or anthropogenic EM energy. Measurements can be made in either the time or frequency domain. Some tools are used to locate metals or utilities; others are used to create conductivity–depth models of the subsurface. If external constraints are available, conductivity–depth models can be transformed into geologic models.

Modified from “Introduction to Geotechnical Geophysics – N. Anderson and N. Croxton, Circular – Number E-C130, October 2008”.

EM systems vary in shape and size based on the project requirement. Most of the EM systems are operated by one person, but some require 2 operators.

All EM systems operated by Scurbat are hand-carried or towed by vehicle along pre-determined lines.

Contoured plot of EM (Frequency Domain) conductivity (mS/m) data at 1m, 3m and 6m depth.

 

Contoured plot of EM (Frequency Domain) data to map the lateral limits of a landfill and potential leachates (red). Area approx. 900m X 500m and 20m EM line spacing.

 

What are the most common uses of Electromagnetic (EM)?

Buried waste drums detection
Contaminant plumes detection and delineation
Landfill extent delineation and quantification
Land salinity assessment
Aquifer/aquitard delineation
Fill delineation

Electromagnetic FAQs

What is an Electromagnetic (EM) survey?

There are many electromagnetic (EM) survey methods. However, all methods, are based on the induction via transmitter coil of an electric or magnetic field in the surface (primary field) produced from a natural or an artificial current source. The primary field propagates trough the sub-surface, inducing currents in the different subsurface materials. This magnetic field variation induces eddy currents. These currents give rise to secondary EM fields, which is then recorded at the surface by a receiver coil.

What is the difference between Frequency and Time Domain Electromagnetic?

In the Frequency Domain Electromagnetic (FDEM) methods the primary field is transmitted continuously, usually as a sine wave of a single frequency, which will detect near surface conductors through the secondary magnetic fields.
In the Time Domain Electromagnetic (TDEM) methods the primary field is switched off soon after induction and the subsurface conductor is detected by observing the decay of the secondary magnetic fields with respect to time

How much does an Electromagnetic (EM) survey cost?

As the applications for EM are several, as well as the type of EM systems, it is difficult, and misleading, to provide an exact dollar value. A very indicative cost for the fieldwork component can vary from $1,500 to $4,500 per day. This excludes mobilisation and demobilisation, which can vary by 10s of thousands of dollars, Australia is big! Also, it excludes processing and reporting, which depends on the amount of data acquired.

Reach Out and Let’s Discuss Your Project

No matter how simple or complex is your project, we can assist in many ways…a technical explanation? A practical field implementation? A budget discussion? Or a full project planning and execution? Just ask away.
Contact Us