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⊥
- curves observed at the epicentre of the deep con-
Fig. 9.4
Transverse apparent-resistivity
ductive zone (
y
=
0) in the model from Fig. 9.3 with fixed parameters
1
=
10 Ohm
·
m
,
,
3
,
3
h
1
=
1km
,
2
=
100000 Ohm
·
m
,
h
2
=
19 km
=
1000 Ohm
·
m
=
10 Ohm
·
m
,
h
3
=
15 km
,
4
=
1000 Ohm
·
m
,
h
4
=
65 km
,
5
=
10 Ohm
·
m and variable parameters
v
=
25
,
100
,
250
,
500 km;
f
=
1
,
5
,
10 Ohm
·
m; 1 - locally normal curves ˙
n
,
¨
n
, 2 - transverse
⊥
- curves in the presence of conductive faults (
q
=
5 km), curve parameter:
f
,
Ohm
·
m, 3 -
⊥
- curve in the absence of conductive faults (
q
transverse
=
0)
⊥
- curves slightly
flatten still preserving their bell-like shape without distinct evidences of a conduc-
tive zone. The different pattern is observed when conductive faults are present. Even
relatively narrow conductive zone (
When widening the conductive zone (
ν
=
250
,
500 km), the
⊥
-
curves with a descending branch, which enables one to estimate a depth to this zone.
Here the deep
S
- effect is clearly observable (at low-frequencies the descending
branch of the
w
=
25
,
100 km) manifests itself in the
⊥
- curves is shifted downwards with respect to the locally normal ¨
n
- curve connected with a central segment of the model). When widening the conduc-
tive zone (
ν
=
250
,
500 km), the deep
S
- effect attenuates and the low-frequency
⊥
- curves approach the locally normal ¨
branches of the
n
- curve. The lower the
fault resistivity, the weaker the deep
S
- effect and the closer the
⊥
- curve to the
normalcy. In the case
ν
=
250 km
,
f
=
1Ohm
·
mor
ν
=
500 km,
f
=
5Ohm
·
m
⊥
- curve virtually comes to the normalcy and provides the reliable 1D
inversion.
The calculations show that highly resistive layers of the continental lithosphere
(10000
the
÷
·
m) forbid the galvanic access to the deep conductive zones
(the screening effect). If the net of deep conductive faults crossing the continental
100000 Ohm
