Dynamic slab segmentation due to brittle-ductile damage in the outer rise

Area of Science:

• Geophysics
• Tectonics
• Earth Science

Background:

• Subduction is a primary driver of plate tectonics and Earth's thermochemical evolution.
• Subducting plates undergo significant normal faulting during bending at the outer rise and trenches.

Purpose of the Study:

• To investigate the consequences of bending-induced plate damage on subduction dynamics.
• To model the interplay between brittle and ductile deformation, including grain damage, during subduction.

Main Methods:

• Numerical subduction modeling.
• Self-consistent tracking of brittle and ductile deformation, including grain damage.
• Analysis of slab weakening and segmentation.

Main Results:

• Pervasive slab weakening and segmentation occur due to coupled brittle and ductile damage localization at the outer rise.
• This slab-damage phenomenon explains the strong plate/weak slab dichotomy, normal fault development, seismic anomalies, and viscosity reductions near trenches.
• Brittle-viscously damaged slabs tend to detach at higher mantle temperatures.

Conclusions:

• Bending-induced slab damage is a key process controlling subduction zone characteristics.
• The findings reconcile observations of strong plates and weak slabs, faulting, seismic anomalies, and viscosity variations.
• Intermittent subduction with frequent slab break-off may have been more common throughout Earth's history than previously thought.