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Lecture 6: Transforms faults and Convergent margins

Lecture 6: Transforms faults and Convergent margins. Kane FZ. South Atlantic Spreading Rate. EPR 9° North. Compression. Cocos plate. Pacific plate. Extension. Gravity. Bain FZ: Multiple new FZs under extension FZs re-combine under compression. 34. 21. 34. 21. 21. 34. 21. 34.

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Lecture 6: Transforms faults and Convergent margins

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  1. Lecture 6: Transforms faults and Convergent margins

  2. Kane FZ

  3. South Atlantic Spreading Rate

  4. EPR 9° North Compression Cocos plate Pacific plate Extension

  5. Gravity

  6. Bain FZ: Multiple new FZs under extension FZs re-combine under compression 34 21 34 21 21 34 21 34

  7. Udintsev FZ, Pac-Ant Ridge Note: Transverse ridges

  8. Also know as “J structures”

  9. Pitman FZ, Pac-Ant Ridge Note: J structures and Transverse ridges

  10. Hawaii: classic flexural bulge due to load of seamounts

  11. Satellite gravity

  12. Kuril Trench: classic example of flexure at a trench

  13. Flexure cause by differential subsidence

  14. Gravity anomalies due to flexure across fracture zones Menard FZ Udintsev FZ Eltanin FZ

  15. Convergent Margins Focal Depths: green < 50 km, yellow = 50 to 250 km, red > 250 km

  16. KK&V Fig 9.1

  17. ocean - ocean M&T ocean - continent KK&V Fig 9.18

  18. Focal Depths: green < 50 km, yellow = 50 to 250 km, red > 250 km

  19. Focal Depths: Green = 0 – 50 km Yellow = 50 – 250 km Red = > 250 km

  20. Ontong Java Plateau Note: Collision of Ontong Java Plateau with trench around 15 Ma led to reversal of subduction “polarity” in SW Pacific

  21. For EQ of size small w.r.t wavelength

  22. For earthquakes at plate boundaries

  23. Note: these are cross sections of beach balls

  24. Double Benioff Zone KK&V Fig 9.12 Upper plane: metamorphic reactions in subducted crust Lower plane: metamorphic reactions in subducted mantle

  25. Ontong Java Plateau Tonga Trench

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