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Published byDillan Williamson Modified about 1 year ago

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Subduction modeling From 2D to 3D…

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

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

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Plate tectonics

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Transform boundaries

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Plate tectonics Divergent boundaries

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Plate tectonics Convergent boundaries

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Plate tectonics Convergent boundaries Collision Subduction

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

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First subduction model : 2D Rectangle domain Plate Upper mantle

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

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

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

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

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

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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

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Rheology Viscous mantle Viscoplastic plate ViscousPlastic

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

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The hardware UQ

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2D subduction results

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Velocity field : vortex

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Lifecycle : initiation

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Lifecycle : flow reorganization

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Limits of the 2D model

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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

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

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

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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

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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

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

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

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

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Edge of the slab extreme case: free slip tear zone

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Top boundary condition plate bottom fixed

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Sides boundary conditions Freeslip on the sides

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3D subduction results

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Velocity field : toroidal flow

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Lifecycle of the subduction

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Initiation

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Reorganization of the flow

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

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

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

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

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

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

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Hinge from the top 20 My40 My60 My 80 My

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Why arcs ? Ping pong ball hypothesis

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

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

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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

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First results

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

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