CONTROLLED – SOURCE RADIOMAGNETOTELLURIC SOUNDINGS SYSTEM

PURPOSE:

Controlled source radiomagnetotellurics (RMT-CS) is intended for application of the RMT technique in remote regions where there are no possibilities to measure enough radio-transmitter’s signals to provide the standard RMT measurements in frequency range 10-1000 kHz and work is usually fulfilled in the frequency range 10-30 kHz in the VLF profiling mode. Using of controlled source (generator and grounded cable) allow us to realize work in the sounding mode. Because the lower frequency limit is downed from 10 kHz in the standard RMT method to 1 kHz the investigation depth in the RMT-CS method reaches up to approximately 100 m for sedimentary sections (three times more than in the standard RMT method). CSRMT measurements results are presented as apparent resistivity and impedance phase curves used for the inversion procedures and obtaining of geoelectric sections.

AREAS OF APPLICATION:

Geological mapping, exploration, hydro geological and building construction works, environmental investigations.

FEATURES OF THE RECEIVER:

• recording of time series or spectrograms of electric and magnetic fields signals, apparent resistivity and impedance phase calculation directly in the recorder, visualization of spectral parameters at the display and estimation of data quality directly at a sounding station, data recording into built-in memory or external PC;
• settings of measurement parameters using both keypad of the recorder and external PC, coordinate and time determination using a GPS receiver;
• electric field measurements using grounded and ungrounded (capacitive) electric lines allow fulfilling works in winter time (on snow and ice) and in summer at the adverse for groundings conditions (asphalt, concrete, gravel);
• using of several (3-4) basic frequencies of the controlled source in the frequency range 1-150 kHz and their odd harmonics (7-9 ones from each basic frequency) provides measurements of detailed (35-40 points) sounding curves in 1 – 1000 kHz band;
• used plane wave model ensures the reliable data interpretation, well developed 1D and 2D inversion software tools allow us to obtain geoelectric parameters of different geological objects;
• depth of investigations is from 2-3 m to 100 m;
• RMT-CS measurements are 80-100 sounding station per day – approximately 10 times faster than VES method of same investigation depth.