Impact of Aseismic Ridges on Subduction Systems: Insights From Analog Modeling

Abstract

The influence of aseismic ridges on subduction kinematics and dynamics, and on the deformation of the overriding plate, remains a topic of debate. This study presents laboratory‐based geodynamic models that simulate the process of aseismic ridge subduction below an overriding plate. The analog experiments show that, depending on its size, subduction of an aseismic ridge can impact on the kinematics of subduction, overriding plate deformation and, to a lower extent, on the geometry of the slab and that of the trench. Specifically, it can cause a reduction of the subducting plate and trench retreat velocities, decreases overriding plate extension and even drives local forearc shortening for the widest ridge, increases the slab dip angle next to the aseismic ridge, but decreases the dip angle at the aseismic ridge in case the ridge is thick and wide, and produces a local perturbation (indentation) of the trench geometry. The magnitude of the described modifications relies to a comparable extent on aseismic ridge width and thickness. The effects of aseismic ridge subduction observed in our models compare to those of the Louisville Seamount Chain, the Cocos Ridge, and the d'Entrecasteaux Ridge system in nature and provide an explanation for the local deformation observed at these subduction zones.

Control of Subduction Zone Age and Size on Flat Slab Subduction

“…This implies that buoyant ridge/plateau subduction is not sufficient on its own to cause flat slab subduction, in agreement with earlier work on Nazca Ridge subduction (Antonijevic et al, 2015). It is also consistent with recent geodynamic experiments of buoyancy-driven subduction with an aseismic ridge, indicating that subduction of a large ridge (e.g., Carnegie Ridge or Nazca Ridge) reduces the slab dip angle in the shallow part of the upper mantle by a mere ∼10 • and does not produce flat slab subduction on its own (Flórez-Rodríguez et al, 2019).…”

Pacific subduction control on Asian continental deformation including Tibetan extension and eastward extrusion tectonics

“…There are also reports of short-lived (~1–2 Myr) inversion and compression for older times along the East and Southeast Asian margins, such as during the late Oligocene in the southern Sumatra basin 39 and the Chezhen basin, a sub-basin of the Bohai basin in Northeast China 40 . Such local, short-lived phases of overriding plate compression and shortening can be explained, for example, by subduction of a short aseismic ridge or small oceanic plateau 41 . These phases of compression, shortening and inversion are thus local and lasted only for a short duration, while the overall, large-scale, tectonics of East and Southeast Asia during most of the Cenozoic has been dominated by extension, as is evident from Fig.…”

Thermo‐Mechanical Numerical Modeling of the South American Subduction Zone: A Multi‐Parametric Investigation

“…Note that the lower and upper limits might actually be between 7 and 14 MPa, and 21 and 28 MPa, respectively. This is moreover consistent with previous work suggesting that subduction zones have a weak interface of which the strength varies very little between different subduction systems (Duarte et al., 2015), with low estimates of the shear stresses at the subduction megathrust in nature (Grevemeyer et al., 2003; Luttrell et al., 2011; Magee & Zoback, 1993; Seno, 2009; Springer, 1999; Wang et al., 1995) and with laboratory and numerical subduction models making use of a very weak subduction interface to sustain subduction (Chen et al., 2015; Crameri et al., 2012; Crameri & Tackley, 2015; Duarte et al., 2014; Flórez‐Rodríguez et al., 2019; Gerya et al., 2008).…”