Sediments and Subduction Interface Mechanics: from micro-scale creep to global plate tectonics

ended

This project seeks to test the hypothesis that sediment subduction strongly influences both the short-term (seismic) and long-term (million-year) mechanical behavior of the subduction interface. The underlying basis of this hypothesis is the possibility that sediments exhibit fundamentally different frictional and viscous properties than subducted mafic oceanic rocks— specifically that sediments are weaker at all conditions along the plate interface. To test this hypothesis, I have split my approach into three complementary and carefully linked tasks, including Task I. Observations from Exhumed rocks, Task II: Rock Deformation Experiments, and Task III: Numerical Modeling. Task I will involve field geological campaigns in three sites representing different conditions of the plate interface, from shallow to deep. Task II will involve three suites of experiments (closely linked to the field sites) aimed at quantifying the rheological properties of mafic rocks at different pressure-temperature conditions. Task III will involve two types of numerical models: 1) seismo-thermo-mechanical modeling aimed at assessing the influence of heterogeneity on seismic slip behaviors, and 2) large-scale mantle convection modeling aimed at quantifying relationships and feedbacks between subduction interface rheology and plate speeds. This research has high potential to impact a number of Earth Science and related disciplines: establishing a lithological control on plate boundary strength, and hence on both subduction seismic behaviours and plate speeds, would establish a fundamental link between plate tectonics, climate, and life on planet Earth.