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H
y
o
Z
N
+
(
r
)
,
E
x
E
x
(
r
)
H
x
o
J
E2
J
E1
x
E
x
(
r
)
=
+
=
(
r
)
+
x
(1
.
20)
H
x
o
−
(
r
)
+
E
y
E
y
(
r
)
J
E2
y
H
y
o
J
E1
E
y
(
r
)
=
+
=
Z
N
+
(
r
)
,
y
H
y
o
Z
N
+
(
r
B
)
,
E
x
E
x
(
r
B
)
H
x
o
J
E2
x
J
E1
x
E
x
(
r
B
)
=
+
=
(
r
B
)
+
(1
.
21)
H
x
o
−
(
r
B
)
+
E
y
E
y
(
r
B
)
J
E2
y
H
y
o
J
E1
E
y
(
r
B
)
=
+
=
Z
N
+
(
r
B
)
.
y
Eliminating
H
x
o
,
H
y
o
from (1.20) and (1.21), we get
|
E
(
r
)
=
[
D
(
r
r
B
)]
E
(
r
B
)
,
(1
.
22)
where
E
x
(
r
)
E
x
(
r
B
)
E
(
r
)
=
,
E
(
r
B
)
=
E
y
(
r
)
E
y
(
r
B
)
and
D
xx
(
r
|
r
B
)
D
xy
(
r
|
r
B
)
[
D
(
r
|
r
B
)]
=
D
yx
(
r
|
r
B
)
D
yy
(
r
|
r
B
)
J
E
2
x
−
1
J
E
2
x
J
E
1
x
J
E
1
x
(
r
)
Z
N
+
(
r
)
(
r
B
)
Z
N
+
(
r
B
)
=
.
J
E
2
y
J
E
1
y
J
E
2
y
J
E
1
y
−
Z
N
+
(
r
)
(
r
)
−
Z
N
+
(
r
B
)
(
r
B
)
r
B
)] was introduced by Doll into the telluric current
method about 70 years ago. We will refer it as the
Doll tensor
. The basic result
of a telluric prospecting was given in a map showing
effective electric intensity
defined as
Recall that the tensor [
D
(r
|
D
eff
=
|
det[
D
(r
|
r
B
)]
|
.
(1
.
23)
Summing up, we should say some words about stability of the impedance rela-
tions. The experience of manifold MTS-soundings carried out at the middle and
low latitudes in the frequency range from 10
2
to 10
-4
Hz suggests that modern
noise-suppressing methods of MT-date processing (mathematical filtration, admit-
tance control, remote reference magnetotellurics, robust statistics, monitoring of
impedance scattering) may provide the impedance estimation with a scattering of
2-3% in modulus and 2-3
◦
in phase (Gamble et al., 1979; Chave et al.,1987; Jones
et al., 1989; Berdichevsky et al., 1989a; Larsen, 1989; Larsen et al., 1996). The
most reliable and stable result can be obtained using the MT-data processing which
reinforces the remote reference magnetotellurics with robust statistics.
