Influence of lateral slab edge distance on plate velocity, trench velocity, and subduction partitioning

Abstract

Subduction of oceanic lithosphere occurs through both trenchward subducting plate motion and trench retreat. We investigate how subducting plate velocity, trench velocity and the partitioning of these two velocity components vary for individual subduction zone segments as a function of proximity to the closest lateral slab edge (DSE). We present a global compilation for 207 trench segments from 17 active subduction zones on Earth and three-dimensional numerical models of progressive free subduction of a single oceanic plate that subducts into a stratified mantle. The results show that the subducting plate velocity is always high (≥5.1 cm/yr (models) and ≤4.2 cm/yr (nature)) and trench velocity is always low (≥2.5 cm/yr (models) and ≤1.7 cm/yr (nature)) in the center of wide subduction zones (DSE > 2200 km). Only in regions close to lateral slab edges (DSE < 1000 km), be it for narrow or wide subduction zones, can the trench velocity exceed 4 cm/yr (models) and 6 cm/yr (nature) and can the subducting plate velocity go below 4 cm/yr (models) and 2 cm/yr (nature). In general, plate velocities, trench velocities and subduction partitioning are much more variable near slab edges than in the center of wide subduction zones owing to other parameters that affect subduction kinematics. We conclude that subduction kinematics can vary considerably along individual subduction zones and that the upper bound values for trench velocity and lower bound values for subducting plate velocity and subduction partitioning at individual subduction zone segments depend critically on DSE. Copyright 2011 by the American Geophysical Union.