The dynamical control of subduction parameters on surface topography

Abstract

The long‐wavelength surface deflection of Earth's outermost rocky shell is mainly controlled by large‐scale dynamic processes like isostasy or mantle flow. The largest topographic amplitudes are therefore observed at plate boundaries due to the presence of large thermal heterogeneities and strong tectonic forces. Distinct vertical surface deflections are particularly apparent at convergent plate boundaries mostly due to the convergence and asymmetric sinking of the plates. Having a mantle convection model with a free surface that is able to reproduce both realistic single‐sided subduction and long‐wavelength surface topography self‐consistently, we are now able to better investigate this interaction. We separate the topographic signal into distinct features and quantify the individual topographic contribution of several controlling subduction parameters. Results are diagnosed by splitting the topographic signal into isostatic and residual components, and by considering various physical aspects like viscous dissipation during plate bending. Performing several systematic suites of experiments, we are then able to quantify the topographic impact of the buoyancy, rheology, and geometry of the subduction‐zone system to each and every topographic feature at a subduction zone and to provide corresponding scaling laws. We identify slab dip and, slightly less importantly, slab buoyancy as the major agents controlling surface topography at subduction zones on Earth. Only the island‐arc high and the back‐arc depression extent are mainly controlled by plate strength. Overall, his modeling study sets the basis to better constrain deep‐seated mantle structures and their physical properties via the observed surface topography on present‐day Earth and back through time.

Overriding Plate Velocity Control on Surface Topography in 2‐D Models of Subduction Zones

“…Accordingly, the arc‐trench distances in present‐day subduction zones lie mostly within the range 150–300 km (e.g., Syracuse & Abers, ). Other profound differences exist between the results reported by Crameri et al () and ours, which may be caused by the different assumptions on rheology. They might also highlight the effect of the OP velocity.…”

“…Their models, limited to the slab‐sinking phase, consistently show the development of a bulge and a relatively large and deep depression. Unlike other studies, Crameri et al () suggested that the bulge corresponds to the island arc and the depression to a back‐arc depression. Although no details are given by the authors on the horizontal distance between the trench and the bulge that their models produce, we can roughly estimate it to be about 100 km.…”

“…The OP topography during the slab‐sinking phase and its dependence on plates and mantle mechanical parameters have been analyzed in number of previous studies (Bonnardot et al, ; Crameri et al, ; Dasgupta & Mandal, ; Hampel & Pfiffner, ; Hassani et al, ; Shemenda, ). Hence, here we focus on the OP topography after the first interaction between the slab and the base of the upper mantle, when the system has reached a quasi steady state.…”

“…The modeling studies that have analyzed the subduction‐induced OP topography have principally focused on the first stage of slab sinking through the upper mantle (Bonnardot et al, ; Crameri et al, ; Hassani et al, ; Hampel & Pfiffner, ; Zhong & Gurnis, ). In contrast, our study focuses on the stage of quasi steady state after slab anchoring at the base of the upper mantle.…”

“…Since the values of relaxation times are relatively low, our models can be compared to the topography that develops in models without elasticity (e.g., Zhong & Gurnis, ). For instance, Crameri et al () carried out a detailed parametric study to evaluate the influence of a range of physical and geometric parameters on topography in free subduction models with viscoplastic plates (temperature‐dependent viscosity). Their models, limited to the slab‐sinking phase, consistently show the development of a bulge and a relatively large and deep depression.…”