Transient Magnetotelluric Imaging of a Buried Valley

1
Transient Magnetotelluric Imaging of a Buried
Valley
2
Introduction

• MT involves the measurement of naturally
  occurring magnetic and electric field
  oscillations.
• The largest naturally occurring signals in the
  audio bandwidth are transients due to individual
  lightning discharges.

3
(No Transcript)
4
Introduction

• Time localized recording of transient energy
  results in the best possible signal-to-noise
  ratio.
• However, transient data displays very strong
  linear polarization.
• The polarization diversity of recorded transients
  can affect the estimation of the impedance
  tensor.

5
(No Transcript)
6
(No Transcript)
7
(No Transcript)
8
Theory
The impedance tensor Z(w) maps magnetic field
oscillations H(w) onto electric field
oscillations E(w) as
9
Theory (1D isotropic earth)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
Conclusions

• The largest naturally occurring signals in the
  audio bandwidth are transients. In order to
  record transients, a time localized recording is
  desired.
• Our Adaptive Polarization Stacking algorithm
  properly incorporates the polarization properties
  of the source field into its analysis.
• The effectiveness of the algorithm is shown in
  the mapping of a buried valley system and the
  good agreement with previous work in the area.

16
(No Transcript)
17
Acknowledgements
I would like to thank my wife for her help during
the field work of this project, Dr. Shawn
Goldak for his theoretical analysis of our APS
algorithm, the Saskatchewan Research Council for
releasing their EM-47 data to me and Cameco
Corporation for the use of their computing
facilities in the inversion of the EM-47 data.