Specifications

University of Pretoria etd – Combrinck, M (2006)
y = 0.0333x + 5E-15
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0 100 200 300 400 500 600 700 800 900 1000
Depth [m]
Conductance [S]
Equivalent Current Filament
Electric Field Maxima
Figure 4-17: Cumulative conductance curves for late time halfsapce approximations.
Looking specifically at depths, the equivalent current filament depths range from 99 m to
920 m, while the electric field maxima map between 63 m and 577 m. The S-layer
transform is also based on using current filaments to approximate a whole earth response
and is it reasonable to expect that the S-layer transform will give similar errors in the depth
to current maxima results.
In Figure 4.18 the cumulative conductance curve (green) of the S-layer differential
transform is compared with the curves from Figure 4.17. It shows the same approximate
depth range as that of the single equivalent current filament but with conductance values
much lower than expected (resulting in underestimation of conductivity values). Based on
these graphs the third set of correction factors is proposed which will transform the S-layer
transform values to coincide with the maxima of the electric field. The corrected
conductance curve is shown in pink (Figure 4.18).
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