"An example of 3D conductivity mapping using the TEMPEST airborne electromagnetic system" by Richard Lane *, Andy Green +, Chris Golding *, Matt Owers *, Caleb Plunkett *, Phil Pik +, Daniel Sattel *, Bob Thorn + (* CRC AMET (Fugro Airborne Surveys), + CRC AMET (CSIRO)). This is a presentation given at the ASEG Conference, March 2000, Hobart, Tasmania, Australia. For further information, please see ; Lane, R., Green, A., Golding, C., Owers, M., Plunkett, C., Pik, P., Sattel, D., Thorn, B., 2000: An example of 3D conductivity mapping using the TEMPEST airborne electromagnetic system, Exploration Geophysics, 31, 162-172.

1. An example of 3D conductivity
mapping using the TEMPEST
airborne electromagnetic
system
Richard Lane*, Andy Green†, Chris Golding*, Matt Owers*, Caleb
Plunkett*, Phil Pik†, Daniel Sattel*, Bob Thorn†
CRC AMET
* Fugro Airborne Surveys † CSIRO

2. TEMPEST Design Philosophy
To provide broadband AEM data for quantitative
applications and interpretation

3. TEMPEST Attributes
• Broadband (25 Hz to >27 kHz)
• 50 % duty cycle, square transmitter current waveform for
strong excitation of secondary currents in conductors
• Pre-stack sferic suppression
• (Variable length) tapered stacking for coil motion and
powerline noise suppression
• Deconvolution processing for removal of the system
transfer function and variations in transmitter current
waveform shape and/or amplitude
• Simplicity of 100% duty cycle square B-field output for
imaging and interpretation
• Approximate corrections for variations in system geometry
• Linkages with modelling routines eg layered inversions
and Conductivity Depth Imaging (CDI) )

4. Bandwidth
• “Bandwidth” = range of frequencies or delay times
over which signal is transmitted and received with
reasonable signal to noise
• High frequency = limited depth penetration but good
shallow spatial resolution
• Low frequency = good depth penetration but poor
resolution of shallow features
• Broadband = good depth penetration without loss of
resolution at shallow depths
• Broadband = ideal characteristics for quantitative
modelling (conductivity-depth mapping), able to
differentiate between good and bad conductors,
shallow and deep sources

5. Bandwidth
Comparison of AEM Systems by Frequency Range
TEMPEST
Helicopter,
FD EM
Fixed Wing,
half-sine, TD
EM
10 100 1,000 10,000 100,000
Frequency (Hz)

6. Waveforms

7. Walford Creek
Base Metal Prospect
North-West Queensland
Australia

8. Walford Creek
Walford Creek

9. Walford Creek
NT Qld
Walford Creek
Century

10. Geological Outline

11. Flight Path on Surface Topography

12. Total Magnetic Intensity

13. Location of line 10281 (211600 E)

14. N/S line over shallow Walford East

15. N/S line over shallow Walford East

16. Location of line 10141 (208100 E)

17. N/S line over deeper Walford West

18. N/S line over deeper Walford West

19. Location of section 8030100 N

20. E / W section 8030100 N

21. Interval Conductivity
(20-40 m)

22. Interval Conductivity
(120-140 m)

23. Interval Conductivity
(220-240 m)

24. Interval Conductivity
(320-340 m)

25. Interval Conductivity
(420-440 m)

26. 3D Conductivity
Isosurface for 30 mS/m

27. 3D Conductivity
Near-surface conductors Isosurface for 30 mS/m
stripped away

28. An example of 3D conductivity
mapping using the TEMPEST
airborne electromagnetic
system
Richard Lane*, Andy Green†, Chris Golding*, Matt Owers*, Caleb
Plunkett*, Phil Pik†, Daniel Sattel*, Bob Thorn†
CRC AMET
* Fugro Airborne Surveys † CSIRO