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Subduction modeling

Subduction modeling. From 2D to 3D…. Subduction modeling. About the plate tectonics 2D subduction model 3D subduction model Future works. Subduction modeling. About the plate tectonics 2D subduction model 3D subduction model Future works. Plate tectonics. Plate tectonics.

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Subduction modeling

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  1. Subduction modeling From 2D to 3D…

  2. Subduction modeling • About the plate tectonics • 2D subduction model • 3D subduction model • Future works

  3. Subduction modeling • About the plate tectonics • 2D subduction model • 3D subduction model • Future works

  4. Plate tectonics

  5. Plate tectonics Transformboundaries

  6. Plate tectonics Divergentboundaries

  7. Plate tectonics Convergentboundaries

  8. Plate tectonics Convergentboundaries Collision Subduction

  9. Subduction modeling • About the plate tectonics • 2D subduction model • 3D subduction model • Future works

  10. First subduction model : 2D • Rectangle domain Plate Upper mantle

  11. First subduction model : 2D • Lengths of the domain Plate 660 km 100 km Upper mantle Lower mantle 3120 km

  12. First subduction model : 2D • Boundary conditions Plate Upper mantle No slip Lower mantle

  13. First subduction model : 2D • Boundary conditions Plate Free slip Upper mantle No slip Lower mantle

  14. First subduction model : 2D • Boundary conditions Plate Free slip Upper mantle Free slip Free slip No slip Lower mantle

  15. First subduction model : 2D • Boundary conditions Plate Free slip No slip Upper mantle Free slip Free slip No slip Lower mantle

  16. … conservation of mass, incompressible medium … conservation of momentum with … deviatoric stress tensor no energy equation Governing equations • Rayleigh-Taylor Instability: dense slab sinks into a less dense mantle

  17. Rheology • Viscous mantle • Viscoplastic plate Viscous Plastic

  18. The software EscriptFinley • Model setup : escript • PDE solver : Finley • Tracking of the plate : level set method • Visualization : Pyvisi, Gnuplot

  19. The hardware • Altix @ UQ

  20. 2D subduction results

  21. Velocity field : vortex

  22. Lifecycle : initiation

  23. Lifecycle : flow reorganization

  24. Limits of the 2D model

  25. Necessity of the third dimension • Importance of the mantle flow • Real subductions have a limited lateral extent • Interactions on the lateral edges of subduction zones

  26. Subduction modeling • About the plate tectonics • 2D subduction model • 3D subduction model • Future works

  27. 3D subduction model • Same governing equations • Same tools used • … only a different setup

  28. 3D subduction model no upper plate plate with subduction zone upper mantle Box size: big enough, for side walls to have little effect on subducting slab

  29. The level set field use level set to define and track the subducting plate subducting slab only subducting part of the plate is included in the FE domain

  30. Symmetry hypothesis free slip side boundary assume symmetry: model only half of the domain

  31. Bottom boundary condition fixed bottom boundary higher viscosity in LM and phase boundary hinder convection

  32. Slab boundary conditions free slip top boundary fixed end plate fixed, to isolate effects of tearing and rollback

  33. Edge of the slab extreme case: free slip tear zone

  34. Top boundary condition plate bottom fixed

  35. Sides boundary conditions Freeslip on the sides

  36. 3D subduction results

  37. Velocity field : toroidal flow

  38. Lifecycle of the subduction

  39. Initiation

  40. Reorganization of the flow

  41. Hinge position Hingeposition(km) Time(M years)

  42. Hinge position Hingeposition(km) Time(M years)

  43. Hinge rollback velocity Hinge rollbackvelocity (mm/year) Time(M years)

  44. Hinge rollback velocity Hinge rollbackvelocity (mm/year) Initiation Time(M years)

  45. Hinge rollback velocity Hinge rollbackvelocity (mm/year) Reorganization of the mantle flow Time(M years)

  46. Hinge rollback velocity Hinge rollbackvelocity (mm/year) 2.5 mm/year Steady subduction Time(M years)

  47. Hinge from the top 80 My 20 My 40 My 60 My

  48. Why arcs ? • Ping pong ball hypothesis

  49. Why arcs ? • Toroidal flow • Inhomogeneities in the subducting plate • Tear resistance on the edges

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