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

2. Morphologies, seismicity and plate boundaries Mid-ocean ridge Fracture zone Deep-sea trench Fig. 2

3. Benard (1901) Downwelling Upwelling Planform of thermal convection Fig. 3

4. Bercovich (1995) Fig. 4 Poloidal component Toroidal component Surface velocities

5. Earthquake = Faulting Normal fault Fig. 5 Modified from Paterson (1958)

6. strike dip angle rake or slip angle amount of slip slip vector direction Fault parameters of an earthquake Fault plane Fig. 6  usin cos  /ucos = tan(  ) cos  tan = tan(  )

7. Fig. 7a Focal mechanism of an earthquake

8. Fig. 7b Fault plane Auxiliary plane

9. Fig. 8 Slip vector and auxiliary plane

10. Age distribution of ocean floor Sclater et al. (1981) Fig. 9

11. Tonga Trench East Pacific Rise Ocean floor topography profile Fig. 10

12. Formation of Oceanic Crust Partial melting Melt Basalt Gabbro, Cumulates Detrick et al. (1987) Moho Fig. 11 M.O.R.

13. Decompressional melting Fig. 12 Asthenosphere Melting temperature Start of melting

14. Magnetic anomaly stripes Atlantic Spreading axis Fig. 13 Cox et al. (1967)

15. History of magnetic reversals Harland et al. (1982)Fig. 14

16. RIDGE Planning Office (1989) Basalts are altered (metamorphosed) by hydrothermal circulations. Fig. 15 MOR activities at different spatial scales

17. Sykes (1967) Normal fault-type focal mechanisms Atlantic Fig. 16

18. Normal Faulting Macdonald (1982) Fig. 17 km

19. M.O.R. Transform fault Fracture zone Plate A Plate B M.O.R. Fig. 18 C D ● ● Ridge-ridge transform fault

20. Transform faults Fig. 19 Atlantic Fracture zone

21. Delong et al. (1979) Fig. 20 Fracture zone

22. Focal Mechanisms Engeln et al. (1986) Fig. 21

23. Continental rifting and sea-floor spreading Africa S. America Atlantic Fig. 22 Sibuet & Mascle (1978)

24. Fig. 23 Energy discippation

25. Trench-trench transform Fig. 24

26. Trench-trench type transform fault North Fiji Basin Tonga Vanuatu Fig. 25

27. Two types of convergent boundaries Subduction zone Collision zone Fig. 26

28. Subduction zone Indian Ocean Fig. 27

29. Fig. 28 Karig (1974) Tectonic elements in the subduction zone

30. Fig. 29 Three brothers: earthquakes in subduction zones

31. Eldest brother: 1994 Sanriku (Ms 7.6) Nakayama & Takeo (1997) Fig. 30

32. Wei & Seno (1989) Slip vectors Fig. 31

33.  * =  - p Effective stress w Fig. 32 Lubrication by pore fluid pressure

34. Seafloor topography in the outer-rise region Fig. 33 Cardwell et al. (1976)

35. Seno and Yamanaka (1996) Trench – Outer rise earthquakes Fig. 34 ● : compression ○ : tension Seno and Gonzalez (1987) Compression Tension

36. Seno and Yamanaka (1996) Age/depth of outer-rise earthquakes Depth Black: compression White: tension Fig. 35 Age of the plate (Ma)

37. Matsuzawa et al. (1986) Intermediate-depth earthquakes: Northern Honshu double seismic zone Fig. 36

38. Bonin arc Deep seismicity van der Hilst & Seno (1993) Fig. 37

39. Dehydration embrittlement: Serpentinite Raleigh & Paterson (1965) Fig. 38

40. (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

41. Active faults in Japan Fig. 40

42. Fault-types of active faults in Japan Huzita (1980) Reverse Strike-slip Normal Fig. 41

43. Volcanoes in Japan Volcanic front Fig. 42

44. Accretion: Offscarping at the toe of the trench Seely et al. (1974) Fig. 43

45. Accretionary prism at the Nankai Trough Kuramoto et al. (2000) Trough axis Decollement Fig. 44

46. Geological terranes of Japan Fig. 45 Y. Saito (unpublished material)

47. Subduction zone Collision zone Fig. 46

48. Molnar (1984) Himalayas 300 km Himalayan Frontal ThrustIndus-Zangpo Suture Zone Fig. 47

49. Tapponnier et al. (1982) Fig. 48