Geoscience Reference
In-Depth Information
Table 9.4
Details of some transform faults
Approximate
Approximate
Approximate
truncated
Present
Offset
age contrast
topographic
lithosphere
slip rate
Location
a
thickness
b
(cm yr
−1
)
Name
(km)
(Ma)
relief (km)
(km)
MAR 52
◦
N
Charlie Gibbs
340
20
2.5
50
2.5
MAR 40
◦
N
Kurchatov
22
2
1.5
15
2.5
A)
FAMOUS area:
20
2
1.5
15
2
MAR 37
◦
N
B)
22
2
1
15
2.2
MAR 35
◦
N
Oceanographer
130
12
4
40
2
MAR 30
◦
N
Atlantis
70
6
3
27
2.5
MAR 24
◦
N
Kane
150
11
3
35
2.8
MAR 11
◦
N
Vema
320
20
3
50
3
Romanche
MAR equator
935
60
4
85
3
JdFR 44
◦
N
Blanco
350
10
35
6
JdFR 40
◦
N
Mendocino
1150
27
2
55
2-4
EPR 23
◦
N
Tamayo
80
3
1
20
6
EPR 10
◦
N
Clipperton
85
1.5
1
14
11
EPR 5
◦
S
Gofar
180
2
2
15
15
EPR 9
◦
S
Wilkes
150
2
1
15
15
SWIR 30
◦
E
Andrew Bain
500
-
4
-
1.6
SWIR 57
◦
E
Atlantis II
200
20
3
50
1.6
PAR 58
◦
S
Udintsev
300
10
1
35
6
PAR 55
◦
S
Eltanin system
900
30-34
60
6
a
MAR, Mid-Atlantic Ridge; JdFR, Juan de Fuca Ridge; EPR, East Pacific Rise; SWIR, South West Indian
Ridge; PAR, Pacific-Antarctic Ridge.
b
From Eq. (7.65).
Table 9.4 lists some of the main transform faults on the mid-ocean-ridge
system. Some transform faults, such as the San Andreas Fault in California, occur
on land, but they usually occur between ridge segments at sea. Many Indian and
Pacific transform faults are not listed because data are not yet available for them;
the details of much of the ocean bed remain unknown. Owing to financial and
logistical considerations, the most easily accessible parts of the ocean bed are the
most studied and best understood. The term transform fault is correctly applied
only to the active region of a fault (i.e., the part between the offset ridge segments).
Extending beyond the active region is a zone of fracturing called a
fracture zone
,
or an 'inactive fossil transform fault'; examples are the Kurchatov Fracture Zone
and the Clipperton Fracture Zone (Fig. 9.31, Plate 21). There is no horizontal slip
motion on the fracture zones, but slight vertical adjustments do occur.
Transform faults range from very long to very short. The equatorial trans-
form faults in the Atlantic are many hundreds of kilometres long. However, the
