Geology Reference
In-Depth Information
N
(a)
0.2
(a)
2
0
1
0
+10
φ
2300 Hz
Dip
0.4
1
φ
400 Hz
-10
0
500 m
(b)
+10
+20
10
0
-10
Dip
2
-10
+10
(c)
Dip
3
1000
-10
0
(d)
+10
Dip
4
15
10
5
0
-10
0
50 m
(b)
+10
0
100 m
3
Dip
50
150 m
Fig. 9.28
(a) Dual-frequency airborne EM, (b) ground tilt-angle
EM, (c) magnetic and (d) gravity profiles from the Canadian
Shield. See Question 5. (After Paterson 1967.)
480 Hz
-10
1800 Hz
Fig. 9.26
(a) Tilt-angle profiles from an EM survey near Uchi
Lake, Ontario. (b) Profile 3 repeated with dual-frequency EM
equipment. See Question 2. (After Telford
et al.
1990.)
Ground EM
In phase
10
7
4
φ
φ
10
0
-10
-20
-30
5
4
3
2
1
0
400
2300
Out of phase
2
Gravity
1.0
0.7
0.4
0.2
0
100 m
0.04
0.07
0.1
0.2
0.4 0.7 1.0
2
4
7 10
20
30
σ
t
(S)
Time domain IP
Fig. 9.29
Characteristic curve for an airborne EM system
over a half-plane.
f
400
/
f
2300
is the ratio of peak responses at
400 Hz and 2300 Hz respectively,
s
and
t
are the conductivity
in S m
-1
and thickness of the conductor in metres, respectively.
See Question 5. (After Paterson 1967.)
2
4
6
n
20
40
20
40
80
80
Fig. 9.27
Ground EM profile, Bouguer gravity profile and
chargeability pseudosection representing results from a
double-dipole IP electrode spread, all from a survey in Bahia,
Brazil. See Question 4. (After Palacky & Sena 1979.)
Continued
