Rate (cm/yr)
12
10
8
6
4
2
0
9.5
S. Chile
Maximum known earthquake magnitude, M W
8.2
NE Japan
8.5
Kuriles
9.0
Kamchatka
8.2
Peru
8.5
C. Chile
9 . 0
8.1
C. America
8.8
Colombia
8 . 5
9.1
Aleutians
7.9
Sumatra
8.0
Ryukyus
Alaska
9.2
8 . 0
7.9
New Hebrides
Scotia
7.0
7 . 5
7.5
Caribbean
7 . 0
Marianas
7.2
Izu-Bonin
7.2
7.1
Java
8.1
Kermadec
7.8
New Zealand
Tonga
8.3
160
140
120
100
80
60
40
20
0
Age (Ma)
Seismic coupling
1.2
0.8
0.4
0.0
0
50
100
150
1.2
0.8
0.4
0.0
30
50
70
90
110
Age (Ma)
Rate (mm/yr)
Fig. 5.4-30 Top: Variation in the magnitude (M w ) of
the largest known subduction thrust fault earthquake
between subduction zones as a function of the convergence
rate and age of the subducting lithosphere. (Ruff and
Kanamori, 1980. Phys. Earth Planet. Inter., 23, 240–52,
with permission from Elsevier Science.) Bottom: Seismic
coupling fraction estimated from historical seismicity at
various subduction zones. Although most subduction zones
show considerable aseismic slip, there is no obvious
correlation with either age of the subducting lithosphere
(left) or subduction rate (right). (Pacheco et al., 1993.
J. Geophys. Res., 98, 14, 133–59, copyright by the
American Geophysical Union.)
Subduction zones 325
Fig. 5.4-31 Focal depths of flexural earthquakes due to the bending of
subducting plates as they enter the trench. Tensional events occur above
the neutral surface, and compressional events occur below it. The plate
mechanical thickness, H, increases with age, as expected from thermal
models. (After Bodine et al., 1981. J. Geophys. Res., 86, 3695–707,
copyright by the American Geophysical Union.)
Fig. 5.4-32 Large normal faulting earthquakes at trenches, such as the
1965 M s 7.5 Rat Island earthquake, may be due to flexure or failure of the
lithosphere under its own weight. The extent of aftershocks, which appear
not to cut the entire lithosphere, may reflect the extent of rupture or be a
temperature effect. (Wiens and Stein, 1985. Tectonophysics, 116, 143–62,
with permission from Elsevier Science.)
Aleutian trench
300°
600°
900°
main shock,
Mar. 30, 1965
aftershock
50 km
O c e a n ic li th o sp h e re
Depth (km)
0
20
40
60
80
Neutral
surface
0
40
80
120
160
180
Age (Ma)
Brittle
Ductile
tensional
compressional
H
Bending
Lithosphere
Asthenosphere
12
10
8
6
4
2
0
9.5
S. Chile
Maximum known earthquake magnitude, M W
8.2
NE Japan
8.5
Kuriles
9.0
Kamchatka
8.2
Peru
8.5
C. Chile
9 . 0
8.1
C. America
8.8
Colombia
8 . 5
9.1
Aleutians
7.9
Sumatra
8.0
Ryukyus
Alaska
9.2
8 . 0
7.9
New Hebrides
Scotia
7.0
7 . 5
7.5
Caribbean
7 . 0
Marianas
7.2
Izu-Bonin
7.2
7.1
Java
8.1
Kermadec
7.8
New Zealand
Tonga
8.3
160
140
120
100
80
60
40
20
0
Age (Ma)
Seismic coupling
1.2
0.8
0.4
0.0
0
50
100
150
1.2
0.8
0.4
0.0
30
50
70
90
110
Age (Ma)
Rate (mm/yr)
Fig. 5.4-30 Top: Variation in the magnitude (M w ) of
the largest known subduction thrust fault earthquake
between subduction zones as a function of the convergence
rate and age of the subducting lithosphere. (Ruff and
Kanamori, 1980. Phys. Earth Planet. Inter., 23, 240–52,
with permission from Elsevier Science.) Bottom: Seismic
coupling fraction estimated from historical seismicity at
various subduction zones. Although most subduction zones
show considerable aseismic slip, there is no obvious
correlation with either age of the subducting lithosphere
(left) or subduction rate (right). (Pacheco et al., 1993.
J. Geophys. Res., 98, 14, 133–59, copyright by the
American Geophysical Union.)
Subduction zones 325
Fig. 5.4-31 Focal depths of flexural earthquakes due to the bending of
subducting plates as they enter the trench. Tensional events occur above
the neutral surface, and compressional events occur below it. The plate
mechanical thickness, H, increases with age, as expected from thermal
models. (After Bodine et al., 1981. J. Geophys. Res., 86, 3695–707,
copyright by the American Geophysical Union.)
Fig. 5.4-32 Large normal faulting earthquakes at trenches, such as the
1965 M s 7.5 Rat Island earthquake, may be due to flexure or failure of the
lithosphere under its own weight. The extent of aftershocks, which appear
not to cut the entire lithosphere, may reflect the extent of rupture or be a
temperature effect. (Wiens and Stein, 1985. Tectonophysics, 116, 143–62,
with permission from Elsevier Science.)
Aleutian trench
300°
600°
900°
main shock,
Mar. 30, 1965
aftershock
50 km
O c e a n ic li th o sp h e re
Depth (km)
0
20
40
60
80
Neutral
surface
0
40
80
120
160
180
Age (Ma)
Brittle
Ductile
tensional
compressional
H
Bending
Lithosphere
Asthenosphere