Specifications

University of Pretoria etd – Combrinck, M (2006)
contrast cases are predicted accurately although the high contrasts are not accurately
mapped. The two most conductive layers generate underestimated values for conductivity
(Figures 4-32 and 4-33) and might be interpreted to be more resistive than the half space if
the conductivity sections are consulted without reference to the distinctive cumulative
conductance signature.
Next, the effect of layer thickness for the low conductivity contrast scenario is investigated.
Thicknesses of 2 m, 5 m, 10 m, 15 m, 20 m, 50 m and 100m are used (Figures 4-34 to 4-
36). It is important to notice that the anomaly widths remain the same until a critical
thickness is reached and only an increase in amplitude with increasing layer thickness is
seen. Although the top of the layers are well defined, the true thickness and conductivity
are not uniquely determined. Very important, though, is that the high contrast behaviour
of decreasing depths with time is not seen here, no matter how large the conductivity-
thickness product becomes.
1
10
100
0 100 200 300 400 500 600 700
Depth [m]
Cumulative Conductance [S]
2m
5m
10m
15m
20m
50m
100m
Figure 4-34: Cumulative conductance for a 0.2 S/m layer of varying thickness at 150m depth in
a 0.02 S/m half space.
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