Telluric Survey

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Exploration Technique: Telluric Survey

Exploration Technique Information
Exploration Group: Geophysical Techniques
Exploration Sub Group: Electrical Techniques
Parent Exploration Technique: Electromagnetic Sounding Techniques
Information Provided by Technique
Lithology: Rock composition, mineral and clay content
Stratigraphic/Structural: Detection of permeable pathways, fracture zones, faults
Hydrological: Resistivity influenced by porosity, grain size distribution, permeability, fluid saturation, fluid type and phase state of the pore water
Thermal: Resistivity influenced by temperature
Cost Information
Low-End Estimate (USD): 522.2252,222 centUSD
0.522 kUSD
5.2222e-4 MUSD
5.2222e-7 TUSD
/ station
Median Estimate (USD): 1,055.56105,556 centUSD
1.056 kUSD
0.00106 MUSD
1.05556e-6 TUSD
/ station
High-End Estimate (USD): 1,694.44169,444 centUSD
1.694 kUSD
0.00169 MUSD
1.69444e-6 TUSD
/ station
Time Required
Low-End Estimate: 1.67 days0.00457 years
40.08 hours
0.239 weeks
0.0549 months
/ 10 stn
Median Estimate: 3.61 days0.00988 years
86.64 hours
0.516 weeks
0.119 months
/ 10 stn
High-End Estimate: 6.67 days0.0183 years
160.08 hours
0.953 weeks
0.219 months
/ 10 stn
Telluric Survey:
Telluric currents, or earth currents, are generated through electromagnetic induction processes due to natural, passive geomagnetic micropulsations. The measurement of telluric currents enables determination of the strata thickness and resistivity profile with depth.
Other definitions:Wikipedia Reegle

Telluric currents flow in the earth’s subsurface in the form of large, dynamic sheets. Similarly to the magnetotelluric method, the source of the signal is naturally occurring particle interactions in the ionosphere primarily due to solar activity. The distribution of the telluric current density is variable in non-uniform regions and this inhomogeneity is indicative of resistivity contrasts in the subsurface. Thus geological features may be discerned from the measurement of telluric currents in the subsurface.[1]

Use in Geothermal Exploration

Physical Properties
Telluric surveys function based on the same physical principles as a magnetotelluric survey.

See Magnetotelluric Techniques: Physical Properties; Electrical Techniques: Physical Properties
Data Access and Acquisition
The measurement of telluric currents requires four electrodes and a voltmeter. The electrode pairs measure the potential difference at the earth’s surface between two points and perpendicular components of the electrical field are recorded, as shown in the figure below. [1]

Electrode configuration for a telluric survey[1]

Best Practices
• Non-polarizing electrodes are the preferred electrode type to reduce noise and distortion to the measurements.

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