divergent boundary
DESCRIPTION
Three types of plate boundaries. Divergent boundary. Transform fault. Convergent boundary. Fig. 1. Morphologies, seismicity and plate boundaries. Deep-sea trench. Mid-ocean ridge. Fracture zone. Fig. 2. Planform of thermal convection. Downwelling. Upwelling. Benard (1901). Fig. 3. - PowerPoint PPT PresentationTRANSCRIPT
Divergent boundary
Transform fault
Convergent boundary
Three types of plate boundaries
Fig. 1
Morphologies, seismicity and plate boundaries
Mid-ocean ridge
Fracture zone
Deep-sea trench
Fig. 2
Benard (1901)
Downwelling
Upwelling
Planform of thermal convection
Fig. 3
Bercovich (1995)
Fig. 4
Poloidal component
Toroidal component
Surface velocities
Earthquake = Faulting
Normal fault
Fig. 5Modified from Paterson (1958)
δ:
λ:
φ−ψ:
φ: ëñå¸
åXäp
ÉXÉäÉbÉvÉxÉNÉgÉãÇÃï˚å¸
Ç∑Ç◊ÇËäpÅAÉåÉCÉN
φ
u:
u
λ Ç∑Ç◊ÇËó
strike
dip angle
rake or slip angle
amount of slip
slip vector direction
Fault parameters of an earthquake
Fault plane
Fig. 6
ψ
usinλcosδ/ucosλ = tan( ψ)
cosδtanλ = tan( ψ)
A
B
C
D
(a)
Fig. 7a
Focal mechanism of an earthquake
(b)
A
B C
D
Fig. 7b
Fault plane
Auxiliary plane
Fig. 8
Slip vector and auxiliary plane
Age distribution of ocean floor
Sclater et al. (1981)Fig. 9
4
6
km
4000 2000 6000 km
Tonga Trench
East Pacific Rise
Ocean floor topography profile
Fig. 10
Formation of Oceanic Crust
Partial melting
MeltBasalt
Gabbro, Cumulates
Detrick et al. (1987)
Moho
Fig. 11
M.O.R.
T
P
Ts
Tm
Decompressional melting
Fig. 12
Asthenosphere
Melting temperature
Start of melting
Magnetic anomaly stripes
Atlantic
Spreading axis
Fig. 13
Cox et al. (1967)
History of magnetic reversals
Harland et al. (1982) Fig. 14
RIDGE Planning Office(1989)
Basalts are altered (metamorphosed) by hydrothermal circulations.
Fig. 15
MOR activities at different spatial scales
Sykes (1967)
Normal fault-type focal mechanisms
Atlantic
Fig. 16
Normal Faulting
Macdonald (1982) Fig. 17
km
M.O.R.
Transform fault
Fracture zone
Plate APlate B
M.O.R.
Fig. 18
C
D
●
●
Ridge-ridge transform fault
Transform faults
Fig. 19
Atlantic
Fracture zone
Delong et al. (1979)
Fig. 20
Fracture zone
Focal Mechanisms
Engeln et al. (1986)
Fig. 21
Continental rifting and sea-floor spreading
Africa
S. America
Atlantic
Fig. 22
Sibuet & Mascle (1978)
L
l g
MOR
MOR
Transform
l
Fig. 23
Energy discippation
Trench-trench transform
Fig. 24
Trench-trench type transform fault
North Fiji Basin
TongaVanuatu
Fig. 25
Two types of convergent boundaries
Subduction zone Collision zone
Fig. 26
Subduction zone
Indian Ocean
Fig. 27
Fig. 28
Backarc Forearc
Accretionary prism
Outer-rise
Outer trenchslope
Backarc basin Forearcbasin
Inner trenchslope
Volcanic front
Karig (1974)
Tectonic elements in the subduction zone
Fig. 29
ÅúÅú
Åú
Åú
ÅúÅú
Åú
ÅúÅú
Åú
Åú
ÅúÅú
Åú
100 km
Youngest brothersEldest brothers
Middle brothers
Upper plate
Trench
Three brothers: earthquakes in subduction zones
Eldest brother: 1994 Sanriku (Ms 7.6)
Nakayama & Takeo (1997) Fig. 30
110 120 130 140 150 16020
30
40
50
60
Pacific
Okhotsk
Japan Sea
Phil. Sea
Amuria
EurasiaN. America
Wei & Seno (1989)
Slip vectors
Fig. 31
* = - p
Effective stress
w
Fig. 32
Lubrication by pore fluid pressure
Seafloor topography in the outer-rise region
Fig. 33
Cardwell et al. (1976)
Seno and Yamanaka (1996)
Trench – Outer rise earthquakes
Fig. 34
●: compression○: tension
Seno and Gonzalez (1987)
Compression
Tension
Seno and Yamanaka (1996)
Age/depth of outer-rise earthquakes
Depth
Black: compression
White: tension
Fig. 35
Age of the plate (Ma)
Matsuzawa et al. (1986)
Intermediate-depth earthquakes: Northern Honshu double seismic zone
Fig. 36
Bonin arcDeep seismicity
van der Hilst & Seno (1993)
Fig. 37
Dehydration embrittlement: Serpentinite
Raleigh & Paterson (1965)
Fig. 38
(a) Cold slab type (b) Hot slab type
Dehydration from crust
Dehydration from crust
Dehydration from serpentine
Dehydration from serpentine
Dehydration locus for slab seismicity
Yamasaki & Seno (2003)Fig. 39
Active faults in Japan
Fig. 40
Fault-types of activefaults in Japan
Huzita (1980)
Reverse
Strike-slip
Normal
Fig. 41
Volcanoes in Japan
Volcanic front
Fig. 42
Accretion: Offscarping at the toe of the trench
Seely et al. (1974)
Fig. 43
Accretionary prism at the Nankai Trough
Kuramoto et al. (2000)
Trough axis
Decollement
Fig. 44
Geological terranes of Japan
Fig. 45Y. Saito (unpublished material)
Subduction zone
Collision zone
Fig. 46
Molnar (1984)
Himalayas
300 km
Himalayan Frontal Thrust Indus-Zangpo Suture Zone
Fig. 47
Tapponnier et al. (1982)Fig. 48