Information Technology Reference
In-Depth Information
whence
S
1
−
S
1
J
y
E
y
=
1
.
F
+
Summing
J
y
J
y
, we obtain the total current
J
y
and
flowing in sediments:
S
1
−
S
1
J
y
J
y
J
y
E
y
=
+
=
F
.
1
+
Consequently,
S
1
S
1
J
y
S
1
=
F
+
E
y
E
y
(
−
v
≤
y
≤
v
)
=
,
F
+
1
whence
S
1
S
1
+
E
y
(
−
v
≤
y
≤
v
)
F
Z
⊥
(
o
⊥
h
⊥
=
−
v
≤
y
≤
v
)
=−
=−
i
,
,
H
x
F
+
1
which coincides with (9.12).
Using (9.12), we can suggest a simple criterion of slight
S
- effect. Let us believe
that the
S
- effect is slight if deviation of
⊥
from 1 does not exceed 0.2. This
5
S
1
S
1
−
6 when
S
1
S
1
5
S
1
S
1
condition is fulfilled if
F
≥
≥
1
.
2orif
F
≥
4
−
when
S
1
S
1
8.
As an pictorial example we consider the apparent-resistivity curves in the model
from Fig. 9.1. Let us take fixed parameters
≤
0
.
1
,
1
=
10 Ohm
·
m
,
h
1
=
1km
=
200 Ohm
·
m
,ν
=
10 km
,
2
=
10000 Ohm
·
m
,
h
2
=
20 km
,
3
=
0 and variable
m. Here
S
1
S
1
=
÷
,
f
=
÷
·
=
parameters
q
0
1km
1
3Ohm
20. Figure 9.2
⊥
- curves in the model shown in Fig. 9.1. Observation
site is located at the centre of the model (
y
Fig. 9.2
Transverse apparent-resistivity
1
=
0). Model parameters:
=
10 Ohm
·
m
,
h
1
=
,
1
1km
=
200 Ohm
·
m
,ν
=
10 km
,
=
10000 Ohm
·
m
,
h
2
=
20 km
,
q
=
0
,
1km
,
f
=
2
⊥
- curve computed by means of the finite element method,
1
,
3Ohm
·
m
,
=
0; 1 - transverse
3
⊥
- curve computed from analytical solution (9.4), 3 - locally normal ¨
2 - transverse
n
-curve
