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Fig. 7.14
Electric field profiles (TM-mode) in the two-segment model shown in Fig. 7.9;
y
-distance to the boundary between segments. Model parameters:
1
,
1
=
10 Ohm
·
m
=
10
5
Ohm
100 Ohm
·
m
,
h
1
=
1km
,
2
=
·
m
,
h
2
=
99 km
,
3
=
0. Profile parameter: period
T
=
0
.
15
−
1500 s
7.2.3 The Three-Segment Model
Now we consider a model where the upper layer consists of three segments
(Berdichevsky and Jakovlev, 1989; Weaver, 1994). The model is shown in Fig. 7.16.
Here the central segment of resistivity
1
and width 2
v
is bordered by the left and
1
. In this model
right segments of resistivity
⎧
⎨
⎧
⎨
S
1
y
≤−
v
1
y
≤−
v
1
=
1
−
v
≤
≤
v
S
1
=
S
1
−
v
≤
≤
v
y
y
⎩
⎩
(7
.
72)
1
y
≥
v
S
1
y
≥
v
2
>>
1
h
2
>>
h
1
R
2
>>
R
1
3
=
0
,
where
S
1
h
1
/
1
are the longitudinal conductances of the side and
central segments of the upper layer and
R
1
h
1
/
1
,
S
1
=
=
=
h
1
1
,
R
2
=
h
2
2
are the transverse
resistances of the upper and intermediate layers.
Now (7.18) falls in the following two equations with constant coefficients:
d
2
dy
2
Z
⊥
(
y
)
(
g
)
2
(
f
)
2
Z
⊥
(
y
)
(
g
)
2
(
f
)
2
Z
N
−
=−
|
y
| ≥
v
.
(7
73)
(
g
)
2
(
f
)
2
Z
⊥
(
y
)
(
g
)
2
(
f
)
2
Z
N
d
2
dy
2
Z
⊥
(
y
)
−
=−
|
y
| ≤
v,
