HR: 08:00h
AN: T31A-01 INVITED    [Abstracts]
TI: The Role of Slab Width in Determining Trench Migration Velocity and Subduction Zone Curvature: Insight From Numerical Modeling and Global Kinematic Calculations
AU: * Moresi, L
EM: louis.moresi@sci.monash.edu.au
AF: School of Mathematical Sciences, Monash University, Building 28, Monash University, Clayton, Vic 3800, Australia
AU: Schellart, W
EM: wouter.schellart@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra, ACT , Australia
AU: Freeman, J
EM: justin.freeman@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra, ACT , Australia
AU: Stegman, D
EM: dave.stegman@sci.monash.edu.au
AF: School of Mathematical Sciences, Monash University, Building 28, Monash University, Clayton, Vic 3800, Australia
AU: May, D
EM: david.may@sci.monash.edu.au
AF: School of Mathematical Sciences, Monash University, Building 28, Monash University, Clayton, Vic 3800, Australia
AB: Subducting slabs provide the main driving force for plate tectonics and flow in the Earth's mantle. Geodynamic modeling provides insight into the kinematics and dynamics of subduction. Many previous numerical studies modeled subduction either in 2D space or in 3D space with essentially static models. Many early laboratory simulations of subduction only focused on 2D aspects of the modeling. In nature, subduction zones and their associated slabs are three-dimensional features with curved geometries and a limited trench-parallel extent (i.e. limited slab width). In addition, the trench velocity varies significantly along individual trenches (up to 20 cm/yr). Only recently have laboratory and numerical models started to focus on subduction processes in three- dimensional space. Here we present results from numerical simulations of free subduction in a stratified mantle reservoir, showing the progressive evolution of subduction in three-dimensional space. The models specifically investigated the influence of slab width on the subduction process, which was varied between 300 km and 7000 km. The sub-lithospheric upper and lower mantle reservoirs were modeled with linear viscosities, while the plate was modeled with a viscoplastic upper half and a viscous lower half. The results show that the trench migration velocity decreases with increasing slab width. The evolution of the trench geometry is also found to depend on the width of the slab with observed geometries ranging between concave, sub-linear and convex. The numerical results are compared to a new global compilation of trench velocity calculations and to subduction zone geometries on Earth, and are found to explain the first-order global trench migration patterns and subduction zone geometries for subduction zones on Earth ranging from narrow (300 km) to wide (7400 km). It is concluded that the simple rheologies and geometries adopted in the 3D numerical simulations can explain a wide variety of subduction zone characteristics as observed on Earth.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8155 Plate motions: general (3040)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly