Dynamics of single subduction systems using 2D and 3D numerical models

Abstract:

It is well established that subducting slabs play a significant role in plate motions on Earth, yet the forces related to subduction and their interactions are not fully understood. Among the driving forces, slab pull is presumed to be most significant and controlled by slab properties such as strength, density and geometry. Slab pull is resisted by a variety of forces including drag around the surface of the slab and at the bottom of the plate, as well as the plate’s resistance to deformation. The relative strength of these forces determines the mode of subduction and controls subduction velocity and trench evolution. In this study, we present a set of 2D and 3D models to systematically investigate the significance and dynamics of driving and resistive forces and their relations to plate and mantle properties. We simulate mechanical and thermo-mechanical models of subduction using Fluidity, a finite-element code with adaptive gridding for viscous flow. Our 2D models illustrate the importance of basal drag in modulating subduction velocities. Using 3D models, we investigate the role of plate width and lateral variations in strength and buoyancy. We compare the behaviour displayed in our simulations with present and reconstructed plate motions to evaluate modes of subduction in major Earth systems throughout the Cenozoic.