Overriding plate deformation and variability of fore‐arc deformation during subduction: Insight from geodynamic models and application to the Calabria subduction zone

Abstract

In nature, subducting slabs and overriding plate segments bordering subduction zones are generally embedded within larger plates. Such large plates can impose far‐field boundary conditions that influence the style of subduction and overriding plate deformation. Here we present dynamic laboratory models of progressive subduction in three‐dimensional space, in which the far‐field boundary conditions at the trailing edges of the subducting plate (SP) and overriding plate (OP) are varied. Four configurations are presented: Free (both plates free), SP‐Fixed, OP‐Fixed, and SP‐OP‐Fixed. We investigate their impact on the kinematics and dynamics of subduction, particularly focusing on overriding plate deformation. The results indicate that the variation in far‐field boundary conditions has an influence on the slab geometry, subduction partitioning, and trench migration partitioning. Our models also indicate that in natural (narrow) subduction zones, assuming a homogeneous overriding plate, the formation of back‐arc basins (e.g., Tyrrhenian Sea, Aegean Sea, and Scotia Sea) is generally expected to occur at a comparable location (250–700 km from the trench), irrespective of the boundary condition. In addition, our models indicate that the style of fore‐arc deformation (shortening or extension) is influenced by the mobility of the overriding plate through controlling the force normal to the subduction zone interface (trench suction). Our geodynamic model that uses the SP‐OP‐Fixed setup is comparable to the Calabria subduction zone with respect to subduction kinematics, slab geometry, trench curvature, and accretionary configuration. Furthermore, the model can explain back‐arc and fore‐arc extension at the Calabria subduction zone since the latest middle Miocene as a consequence of subduction of the narrow Calabrian slab and the immobility of the subducting African plate and overriding Eurasian plate. This setting induced strong trench suction, driving fore‐arc extension, and forced subduction to be accommodated almost entirely by slab rollback (not trenchward subducting plate motion), while trench retreat was accommodated almost entirely by back‐arc and fore‐arc extension (not trenchward overriding plate motion), comparable to our SP‐OP‐Fixed model.

Boundary Element Modeling of Two‐Plate Interaction at Subduction Zones: Scaling Laws and Application to the Aleutian Subduction Zone

“…The last result regarding the OP deformation concerns the influence of the subduction interface. Our model confirms the short‐range nature of the lubrication forces that develop within the subduction interface, as also reported by Duarte et al () and Chen et al (). In fact, as reported at the end of section 6 varying the thickness of the lubrication layer (i.e., the magnitude of the lubrication forces) influences both the shortening (Figure , right) and the bending of the OP, but only in the forearc region.…”

“…A possible mechanical interpretation of this result is that slab rollback induces a toroidal mantle flow that exerts shear stresses on the base of the OP that in turn lead to backarc opening. The rate of extension in the backarc zone depends on whether the OP is free to move or is fixed at its end on the opposite side from the trench (Chen et al, ). Interestingly, backarc extension is also observed in the 2‐D (toroidal flow absent by definition) numerical model of Holt et al () when the OP is positively buoyant.…”

Geodynamics of divergent double subduction: 3‐D numerical modeling of a Cenozoic example in the Molucca Sea region, Indonesia

“…Migration and deformation of overriding plate are actually controlled by subduction‐induced mantle flow, which imposes basal tractions to the overriding plates, driving their motions and internal extension due to gradient of mantle flow and compression near trench [ Duarte et al , ; Meyer and Schellart , ; Chen et al , ]. A number of previous numerical and laboratory studies for single‐sided subduction suggest that development of this concave shape of slab hinge is predominately controlled by slab width [e.g., Stegman et al , ; Schellart et al , ], thickness and thermal state of the overriding plates [e.g., Meyer and Schellart , ; Rodríguez‐González et al , ; Taramõn et al , ].…”

“…Migration and deformation of overriding plate are actually controlled by subduction-induced mantle flow, which imposes basal tractions to the overriding plates, driving their motions and internal extension due to gradient of mantle flow and compression near trench [Duarte et al, 2013;Meyer and Schellart, 2013;Chen et al, 2015]. A number of previous numerical and laboratory studies for single-sided subduction suggest (e and f) Model DDS_200-150 (left: φ pert = 30°, L pert = 200 km; right: φ pert = 30°, L pert = 150 km, also shown in Movie S4).…”

Contrasting sediment melt and fluid signatures for magma components in the Aeolian Arc: Implications for numerical modeling of subduction systems

“…Also, recent work by Chen et al . [] based on dynamic laboratory models of progressive subduction in three‐dimensional space highlights the possibility of a toroidal asthenosphere return flow induced by the slab rollback of the Ionian Plate. Our new data confirm a sediment melt component at the borders of the arc, possibly connected to hot asthenosphere flow at the edges of the slab responsible for the melt signature (Figure ).…”