What is magnetotellurics (MT) used for?
Magnetotellurics is a passive geophysical technique that uses natural variations of the Earth’s electromagnetic field to map the electrical resistivity of the subsurface, from a few hundred meters to tens of kilometers deep. It complements geological information and other geophysical methods.
3D MT models support decisions in:
- Mineral exploration: deep mineral systems such as porphyries, epithermal and IOCG deposits, and lithium brines in salars.
- Groundwater: hydrogeological studies, when the geology of the area justifies a 3D model.
- Geothermal: characterization of geothermal systems and reservoirs.
Why a 3D model and not 2D?
A 2D inversion assumes that the geology does not change in the direction perpendicular to the profile. It is a good approximation when structures are elongated and data are acquired along profiles, and it gives fast results.
In many exploration settings, such as porphyry, volcanic or geothermal systems, the geology varies in all three directions. There, bodies located off the profile can appear on it in the wrong position or with the wrong resistivity. A 3D inversion makes no assumptions about the geometry of the geology: it lets the subsurface vary in all three directions, uses all stations at once and delivers a volume instead of isolated sections. This places structures (anomalies) more reliably.
What does TerraSur do?
We run the 3D inversion of magnetotelluric data already acquired by the client or its contractor, and deliver the model, its visualizations and a report. We also advise on the quality and use of MT data.
Is the technology ready?
Our technology has been validated with published data (TRL 5) and is now in the pilot stage with industry. We work with companies and contractors that want to apply it to their own data and co-develop the final solution with us. Participants get early access to the technology and work directly with our technical team; in return, we ask for feedback on the results and the process.
What data are needed?
Processed MT data and station locations. In the discovery call we check whether the data are suitable for a 3D inversion.
What is delivered?
The 3D resistivity model, visualizations of the resulting model and a final report with the data used, the modeling setup used and the fit to the observed data. We adapt the technical level of the report to the needs of the client and its team, and review the results together.
Do you work with geophysical contractors?
Yes. We receive the MT data acquired and processed by the contractor and take care of the 3D inversion. As a result, we deliver the resistivity model, its visualizations and a technical report ready to integrate into its report to the client.
Why a Bayesian approach?
In magnetotellurics, different subsurface models can explain the same data. A deterministic inversion returns a single solution; the Bayesian approach explores the set of models consistent with the data and shows which parts of the model can be trusted and which structures are most likely. This uncertainty quantification is under validation. More detail under Technology.
What is model uncertainty and why does it matter?
Every subsurface model has parts that are better supported by the data than others. Uncertainty tells you how much to trust each anomaly found: which ones are robust and which could change with more information. This helps prioritize targets and decide with more confidence where to drill or acquire new data. Our models include a confidence measure for each anomaly, and the way it is presented is adapted to what your team needs.
How does the service work?
The service has four steps: discovery call, data review, 3D inversion, and delivery with a joint review. The details are under How to get started.
How much does it cost and how long does it take?
We quote each project according to its scope: area size, number of stations, period range and deliverables. Timelines are set in the discovery call.
Any other questions?
Write to info@tsgeophysics.cl or book a discovery call from the contact page.