The Role of Sediment Accretion and Buoyancy on Subduction Dynamics and Geometry

Brizzi, Silvia; Becker, T. W.; Faccenna, Claudio; Zelst, Iris van; Zilio, Luca Dal; Dinther, Ylona van

doi:10.1029/2021gl096266

Cited by 10 publications

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“…For example, forearc compression may lead to uplift through thrust faulting and accretion and/or forearc underplating (Clift & Hartley 2007;Menant et al 2020). Depending on material buoyancy, accreting/underplating may also serve to counteract the slab pull force (Keum & So 2021;Brizzi et al 2021). On the other hand, lower shear stresses associated with the weak interface case could lead to normal faulting and potentially decreased topography and local forearc submergence (e.g.…”

Section: Relationships Between Interface Rheology and Forearc Topographymentioning

confidence: 99%

The effects of plate interface rheology on subduction kinematics and dynamics

Holt

Becker

Faccenna

2022

Geophysical Journal International

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Summary Tectonic plate motions predominantly result from a balance between the potential energy change of the subducting slab and viscous dissipation in the mantle, bending lithosphere, and slab–upper plate interface. A wide range of observations from active subduction zones and exhumed rocks suggest that subduction interface shear zone rheology is sensitive to the composition of subducting crustal material— for example, sediments versus mafic igneous oceanic crust. Here we use 2-D numerical models of dynamically consistent subduction to systematically investigate how subduction interface viscosity influences large-scale subduction kinematics and dynamics. Our model consists of an oceanic slab subducting beneath an overriding continental plate. The slab includes an oceanic crustal/weak layer that controls the rheology of the interface. We implement a range of slab and interface strengths and explore how the kinematics respond for an initial upper mantle slab stage, and subsequent quasi-steady-state ponding near a viscosity jump at the 660-km-discontinuity. If material properties are suitably averaged, our results confirm the effect of interface strength on plate motions as based on simplified viscous dissipation analysis: a ∼2 order of magnitude increase in interface viscosity can decrease convergence speeds by ∼1 order of magnitude. However, the full dynamic solutions show a range of interesting behavior including an interplay between interface strength and overriding plate topography and an end-member weak interface-weak slab case that results in slab breakoff/tearing. Additionally, for models with a spatially limited, weak sediment strip embedded in regular interface material, as might be expected for the subduction of different types of oceanic materials through Earth’s history, the transient response of enhanced rollback and subduction velocity is different for strong and weak slabs. Our work substantiates earlier suggestions as to the importance of the plate interface, and expands the range of quantifiable links between plate reorganizations, the nature of the incoming and overriding plate, and the potential geological record.

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