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Magnetotelluric Systems at PASSCAL

Magnetotelluric (MT) methods are used to produce conductivity models of the crust and upper mantle through the recording of geoelectric and geomagnetic field variations at the Earth's surface. Depending on the period of the recordings, these methods can provide results from a few hundred meters depth (short period) to 30 km or deeper (long period). Conductivity is a physical property, which is complementary to seismic velocity, and which is very sensitive to the presence of fluids. When seismic and MT data sets are measured together, the additional data can dramatically improve determinations of the structure of the crust and mantle.



Since 2019, the EPIC (formerly known as PASSCAL) has been developing MT resources to meet PIs needs. We currently have a wide pool of MT equipment including both long-period (LEMI) and wideband (Phoenix) systems.


Model Inventory (01/2024)
LEMI-424 (Digitizer) 12
LEMI-039 (Fluxgate magnetometer) 12
MTU-5C (Digitizer) 21
MTC-150 (Induction coil) 10
MTC-180 (Induction coil) 5
MTC-155 (Induction coil) 10
MTC-185 (Induction coil) 5
ANT/4 (Induction coil) 20
ANT/7 (Induction coil) 10
Borin Stelth 4 Ag-AgCl2 (Electrode) 200
Phoenix Titanium plates (Electrode) 40


    Long-period system                                                                        Wideband system











Over the years, we have developed  detailed testing procedures to evaluate equipment (coils, magnetometers, digitizers, electrodes, ...) coming back from the field or newly acquired. Our goal is to send PIs reliable MT systems so they can record high quality data. We are currently establishing a reference test site to further improve our testing procedures and are looking into telemetry options for both the long-period  and wideband systems to allow for real-time data access. More updates on these topics to come.

Parallel to that effort, we have developed software tools to help with the archiving of MT data and metadata. These tools (lemi2seed and phoenix2seed) offer both command line and graphical user interfaces and are distributed as part of our conda channel. For more information on how to install these tools on your local machine, please see our Software page. These applications are also installed on the field laptops that we send out to each EPIC supported experiment. Third-party software tools (including EMpower, LEMI-424 and KMS-Pro) and field material (field sheets, instrument and software documentation) are also provided on the field laptops.

In the last 2 years (11/2021 - 12/2023), we have supported a total of 4 long-period and 8 wide-band experiments. We have also hosted several short courses including two in-person ones: "Magnetotellurics at PASSCAL, from deployment to data collection" in Summer 2022 at the SAGE/GAGE meeting and "Magnetotelluric Instrumentation and Data Processing Short Course" in Fall 2022 at the EPIC.

For each experiment, we offer logistic, engineering, field, software and data archiving support. We also provide on-site and/or remote training with the instrumentation prior to any deployment.

The MT instruments are available through the conditions stated in the PASSCAL Instrument Use Policy. If interested, MT equipment can be requested online using the Instrument Request Forms.

We are always happy to hear from you. If you have any questions, comments, suggestions and/or feedback, please email us at mt [at] passcal [dot] nmt [dot] edu.