2013/04/23 by Wouter P. Schellart, Louis Moresi · 188 citations
Earth and Planetary Sciences · #Forearc #Geological and Geochemical Analysis #Geology #Geophysics #High-pressure geophysics and materials #Lithosphere #Mantle (geology) #Mantle wedge #Materials science #Oceanic crust #Petrology #Seismology #Shear (geology) #Shear zone #Slab #Slab window #Subduction #Tectonics #Trench #Volcanic arc #earthquake and tectonic studies
paper · pdf · doi:10.1002/jgrb.50173
published in Journal of Geophysical Research Solid Earth 118(6), 3221-3248 (Wiley)
openalex publication_date 2013/04/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Abstract We present numerical subduction models to investigate overriding plate deformation at subduction zones. All models show forearc shortening, resulting predominantly from shear stresses at the subduction zone interface and opposite‐sense mantle shear stresses at the base of the forearc lithosphere. Models dominated by backarc extension show that it results from trench‐normal positive velocity gradients in the mantle below the overriding plate. Such gradients result from toroidal mantle flow induced by slab rollback, with velocities below the leading part of the backarc faster than the overriding plate velocity. The velocity gradients induce basal shear stresses that increase trenchward and cause trenchward overriding plate motion at a velocity ( v OP⊥ ) whose spatial average is below the trench retreat velocity ( v T⊥ ). The combination of basal shear stresses and average v OP⊥ < v T⊥ causes trench‐normal deviatoric tension in the backarc and backarc extension. Models dominated by backarc shortening show that it results from a relatively immobile subduction hinge and trenchward overriding plate motion driven by poloidal mantle flow. The poloidal mantle flow is induced by downdip slab sinking and causes the average v OP⊥ > v T⊥ . This results in trench‐normal deviatoric compression and shortening in the leading part of the overriding plate as it collides with the subduction hinge. Ultimately, the geodynamic models demonstrate that backarc extension is favored for narrow slabs and near lateral slab edges and is driven by rollback induced toroidal mantle flow, while backarc shortening is favored for the center of wide slabs and is driven by poloidal mantle flow resulting from downdip slab motion.