Information Technology Reference
In-Depth Information
Fig. 5.1
Illustrating the
determination of the
generalized impedance tensor
air
earth
V
primary currents of density
j
p
closed in a source domain I located above the Earth.
The centre of the domain I is at a point O, its maximum radius is r
i
.
The electromagnetic field meets here the Maxwell equations
j
p
curl
H
=
E
+
,
curl
E
=
i
o
H
,
z
∈
[
−∞
,
∞
]
.
(5
.
1)
For the normal field excited in the horizontally layered Earth in the absence of
the inhomogeneous domain V we have
curl
H
N
=
N
E
N
curl
E
N
o
H
N
,
=
i
,
z
≥
0
.
(5
.
2)
5.1.1 Analysis of the Normal Magnetotelluric Field
A remarkable feature of the model is that the normal current flows parallel to the
boundary between the conducting Earth and the nonconducting air and the normal
electric field in the Earth has no vertical component (Berdichevsky and Zhdanov,
1984; Zhdanov and Keller, 1994):
E
z
≡
0
,
z
≥
0
.
(5
.
3)
In order to model the normal field, we introduce the following limitations:
- The ma
gnetotell
uric observations are performed on the Earth's surface in the
domain S :
x
2
r
s
. Its centre M
o
coincides with the origin of the coordinate
system,
r
s
is its maximum radius;
+
y
2
≤
