Ambient Noise Tomography (ANT)
A low-cost and minimally invasive passive seismic imaging technique. Transform your mineral exploration strategy with 3D subsurface models up to 1-2 km deep.
What is ANT?
Ambient Noise Tomography (ANT) is a passive seismic imaging technique that utilises naturally occurring background vibrations—generated by ocean waves, atmospheric disturbances, or human activities—to construct highly detailed 3D images of the Earth's subsurface.
Unlike traditional active-source seismic methods that rely on explosives or vibratory trucks, ANT is entirely passive. This makes it a cost-effective and environmentally friendly alternative perfectly suited for early-stage, large-scale mineral exploration.
The Institute of Mine Seismology (IMS) has been pioneering the use of ANT for mineral exploration since 2015, successfully guiding exploration planning for clients globally, even in remote locations with thick cover like the Kalahari Copper Belt.
Compact, standalone wireless nodes are easily deployed in remote locations.
How It Works
By recording continuous ambient noise with a temporary array of wireless seismic nodes, we can reconstruct the Green's function between sensor pairs through cross-correlation.
This allows us to extract surface wave dispersion characteristics. By inverting a large collection of these curves, we generate a 3D volume of shear-wave velocity (S-wave). Regions of anomalous seismic velocity can highlight potential drilling targets.
Advantages of Ambient Noise Surveys
Reduced Drilling Costs
Subsurface models from ANT inform intelligent drilling campaigns. By identifying specific areas of interest within large licence areas, you can eliminate wasteful expenditure. The cost of an entire ANT survey is often equivalent to just one or two deep boreholes.
Large Area Coverage
Nodes spaced 500m to 800m apart allow us to rapidly cover large areas ranging from 50 km² to 200 km² (depending on imaging goals), providing a comprehensive macro-view of regional geology.
Low Environmental Footprint
Surveys involve deploying compact, standalone wireless nodes buried in shallow holes. There is no need for heavy machinery, line clearing, or active sources, making it ideal for environmentally sensitive regions.
Rapid Deployment & Results
A moderately-sized survey typically utilizes 100 to 300 wireless geophones deployed for a 25-day recording period. Shortly after node retrieval, processed data and 3D velocity models are ready for interpretation.
Applications of ANT
- Greenfields Mineral Exploration: Identify large-scale geological structures, faults, and stratigraphy at depth beneath extensive cover (e.g., Kalahari Copper Belt).
- Brownfields (Near-Mine) Exploration: Leverage existing in-mine seismic arrays combined with surface nodes to find near-mine drill targets.
- Tailings Storage Facilities (TSFs): Image internal weaknesses, track spatial velocity changes, and monitor internal erosion or leakage paths over time.
- Geotechnical Investigations: Sub-surface investigations prior to civil works, including void detection and bedrock mapping.
Trusted by Global Mining Leaders
"IMS's ANT surveys provided us with crucial subsurface imaging despite the remote location and thick sandy cover of the Kalahari Copper Belt. The ability to successfully distinguish the Ngwako Pan Formation (NPF) from the D'Kar Formation (DKF) significantly guided our exploration planning and helped convert our targets into drill-ready prospects."
Ready to Optimize Your Exploration Strategy?
From the Western Australian Gold Fields to the Canadian Shield, our team is ready to help you convert potential targets and regional hypotheses into drill-ready prospects.
Contact Our Geophysics Team❯