Divergent boundary Transform fault Convergent boundary Three types of plate boundaries Fig. 1.

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