The project combined fieldwork, experiments, and modeling into a single workflow aimed at connecting real rock properties to real subduction behavior. Field and laboratory studies focused on three main regions that preserve exhumed subduction-interface rocks spanning a range of depths and conditions. Across these sites, we mapped deformation structures and analyzed microstructures to identify systematic differences between sediment-rich and basalt-rich parts of subduction interfaces. A key result is that deep interface deformation is often distributed across a zone rather than localized on a single sharp surface, and that the interface commonly contains a mixture of materials whose geometry and proportions matter mechanically.
In parallel, we carried out high pressure–temperature rock deformation experiments on minerals and rock types representative of subducted oceanic crust. A major outcome is a quantitative description of how important mafic assemblages deform under subduction-zone conditions, allowing direct comparisons to sediment-derived rocks. These experimental constraints translate “weak” and “strong” from qualitative labels into measurable parameters that can be used in models (Fig. 3).
We then developed numerical models at two scales. At the earthquake-cycle scale, models explored how a shear zone that is partly brittle and partly ductile, and that contains heterogeneity, can produce a range of transient slip behaviors, including slow slip. At the plate-tectonic scale, dynamic subduction models quantified how plausible variations in interface strength can influence slab motion, trench migration, and convergence rates (Fig. 2). Together, the modeling demonstrates that interface rheology and internal structure can control both short-term slip signals and long-term subduction dynamics.
The project’s results have been disseminated through peer-reviewed publications, conference presentations, invited talks, and open communication through the project’s public website. The main exploitation of the results is scientific: (i) providing quantitative constraints that can be adopted by the broader modeling community, and (ii) offering a clearer physical interpretation of geophysical signals (such as low-velocity layers and slow earthquakes) in terms of realistic rock types, fluids, and shear-zone architecture.
