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

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Presentation on theme: "Subduction modeling From 2D to 3D…. Subduction modeling About the plate tectonics 2D subduction model 3D subduction model Future works."— Presentation transcript:

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 Transform boundaries

6 Plate tectonics Divergent boundaries

7 Plate tectonics Convergent boundaries

8 Plate tectonics Convergent boundaries 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 3120 km 660 km Plate Upper mantle Lower mantle 100 km

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

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

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

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

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

17 Rheology Viscous mantle Viscoplastic plate ViscousPlastic

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

19 The hardware 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 upper mantle plate with subduction zone no upper plate Box size: big enough, for side walls to have little effect on subducting slab

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

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

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

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

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

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

43 Hinge position Hinge position (km) Time (M years)

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

45 Hinge rollback velocity (mm/year) Time (M years) Initiation

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

47 Hinge rollback velocity (mm/year) Time (M years) Steady subduction 2.5 mm/year

48 Hinge from the top 20 My40 My60 My 80 My

49 Why arcs ? Ping pong ball hypothesis

50 Why arcs ? Toroidal flow Inhomogeneities in the subducting plate Tear resistance on the edges

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

52 To be continued … normal case: tearing follows a pre-existing weak zone subduction possible if slab strength > strength of the weak zone fixed weak zone, part of the FE domain

53 First results

54 Thank you ! Hans Mülhaus Laurent Bourgouin Klaus Gottschaldt … you for coming


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