Very-Low Frequency Electromagnetic Survey (VLF-EM)

In this surveying method magnetic components of the electromagnetic field generated by long-distance radio transmitters in the VLF (Very Low Frequency) band are utilized. These transmitters are used for long- distance communication, and they operate at 15-30 kHz. Conductive structures on the surface or underground, even when covered with thick overburden, affect locally to the direction and strength of the field generated by the transmitted radio signal. The instrument measures the radio signal distortion and presents the result directly on a display screen. Normally, more than one profile will be needed to indicate whether or not the structure is a good drilling target. Running additional parallel profiles shows whether the zone is wide enough to provide a good yield. Depending on the terrain, profiles are run in irregular or regular patterns.


Process of Conducting a VLF-EM Survey:

The process of conducting a VLF-EM survey typically involves the following steps:

  • Survey Design: A geophysical expert designs the survey layout, considering factors such as target depth, and survey area.
  • Instrument Setup: The device is set up for use on site, by scanning the signal. Stronger the signals, better the Results!
  • Data Acquisition: Controlled electrical currents are injected into the ground, and voltage measurements are recorded using the electrode arrays. Multiple measurements are taken at different locations to ensure comprehensive coverage. As designed, multiple readings are taken in a regular interval of 5m or 10m (as per site conditions) in profiles. The entire Survey Area is covered by a pattern of Parallel Profiles run across the Field.
  • Data Processing and Interpretation: The acquired data undergoes sophisticated processing techniques in licensed software. Geoscientists interpret the data to identify subsurface features and analyse the geological characteristics.

Advantages of VLF-EM Surveys:

Implementing VLF-EM surveys offers several key advantages over conventional subsurface exploration methods:

  • Precise Measurements: VLF-EM surveys provide precise measurements in a relatively short span, allowing the Team to cover available land parcel extensively. This not only opens up the best possibilities for drilling but also provides data to allow holistic Solutions to take shape.
  • Non-Destructive and Non-Intrusive: The technique does not require drilling or excavation, minimizing disturbance to the site and reducing costs and environmental impact.
  • Time and Cost Efficiency: VLF-EM surveys are relatively quick to conduct, enabling rapid data collection and analysis. The efficient workflow translates into more land parcel being covered in a day’s work.
  • Best Results in Hardrock: The technique can be applied in various geographical areas, and will provide best result for any hard rock region. This allows us a wide range of applications such as mineral exploration, groundwater studies, engineering investigations, and environmental assessments.
  • Pre-emptive Risk Mitigation: By accurately mapping subsurface features, potential risks such as sinkholes, landslides, and contaminated zones can be identified, enabling proactive risk management strategies.