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Fig. 12.45
Apparent-
resistivity curves in models of
the stable (S) and active
(A) tectonic zones;
1 - locally normal curves
n
n
(ocean),
(continent) and
2 - transverse
⊥
-curves,
3 - longitudinal
-curves.
Parameter of the curves is the
distance to the coast in km.
Resistivities (Ohm
m) and
thicknesses (km) of layers are
shown in the model sections:
a - model
S,
b-model
A
·
is quite different. Their behavior is governed by
the inductive effect. Even in the near-coast zone, they have distinct inflections and
minima indicating the presence of a crustal or crust-mantle conductive layer. At
a distance of about 100 km from the coast, the
with the longitudinal curves
-curves merge with the normal
n
.
In closing, we can compare the resolution of the TM- and TE-modes. It is seen
from Fig. 12.46 that at a distance of 15 km and even of 85 km from the coast the
transverse curves of
curve
S
obtained in models A and S practically coincide
(they differ by no more than 3-5% throughout the period range considered). So,
using the TM-mode in an 85 km wide alongshore zone, it is impossible to dis-
tinguish a crustal conductor 10 km thick from a crust-mantle conductor 114 km
A
and
