Slab width plays a major role in controlling subduction dynamics and
trench motion. However, observations on natural narrow subduction zones
do not show any correlation between slab width and trench velocities,
indicating that other factors may have a greater impact. Here, we use 3D
numerical subduction models to evaluate the effect of slab width,
strength of slab coupling to the lateral plate and overriding plate
thickness on trench kinematics. Model results show that slab width has
little influence on trench migration rates for narrow subduction zones,
but that the thickness of the overriding plate plays a major role, with
trench velocities decreasing as the thickness increases. These results
explain trench velocities observed in natural narrow subduction zones
showing no relation with slab width but an inverse dependence on
overriding plate thickness. Finally, we find that the overriding plate
thickness also significantly affects the trench shape.