Back‐arc strain in subduction zones: Statistical observations versus numerical modeling

Abstract

[1] Recent statistical analysis by Lallemand et al. (2008) of subduction zone parameters revealed that the back-arc deformation mode depends on the combination between the subducting (v sub ) and upper (v up ) plate velocities. No significant strain is recorded in the arc area if plate kinematics verifies v up = 0.5 v sub À 2.3 (cm/a) in the HS3 reference frame. Arc spreading (shortening) occurs if v up is greater (lower) than the preceding relationship. We test this statistical law with numerical models of subduction, by applying constant plate velocities far away from the subduction zone. The subducting lithosphere is free to deform at all depths. We quantify the force applied on the two converging plates to sustain constant surface velocities. The simulated rheology combined viscous (non-Newtonian) and brittle behaviors, and depends on water content. The influence of subduction rate v s is first studied for a fixed upper plate. After 950 km of convergence (steady state slab pull), the transition from extensional to compressive stresses in the upper plate occurs for v s $ 1.4 cm/a. The effect of upper plate velocity is then tested at constant subduction rate. Upper plate retreat (advance) with respect to the trench increases extension (compression) in the arc lithosphere and increases (decreases) the subducting plate dip. Our modeling confirms the statistical kinematic relationship between v sub and v up that describes the transition from extensional to compressive stresses in the arc lithosphere, even if the modeled law is shifted toward higher rates of upper plate retreat, using our set of physical parameters (e.g., 100 km thick subducting oceanic plate) and short-term simulations. Our results make valid the choice of the HS3 reference frame for assessing plate velocity influence on arc tectonic regime. The subduction model suggests that friction along the interplate contact and the mantle Stokes reaction could be the two main forces competing against slab pull for upper mantle subductions. Besides, our simulations show that the arc deformation mode is strongly time dependent.

How collision triggers backarc extension: Insight into Mediterranean style of extension from 3-D numerical models

“…The model with only oceanic subduction shows that although the viscous dissipation in the overriding plate is high, it is not localized enough to open a BAB. In such a setting, BAB formation is still possible through other physical factors that are not taken into account in our models, such as the weakening of the overriding plate due to the presence of fluids and melt (Arcay et al, 2008;Gerya and Meilick, 2011).…”

“…Previous studies helped our understanding of the mechanisms of the BAB formation through 2-D (Arcay et al, 2008;Gerya and Meilick, 2011) and laterally heterogeneous 3-D models (Capitanio and Replumaz, 2013;Li et al, 2013), and the episodicity in backarc tectonic regimes (Clark et al, 2008;Baitsch-Ghirardello et al, 2014). However, until now, all these aspects have been studied separately.…”

Subduction-transition zone interaction: A review

“…While the subducting plate generally drives trench motion, interplate coupling and upper-plate forcing provide resistance. In some cases, the upper plate may provide an additional driving force Arcay et al, 2008;Van Dinther et al, 2010;Čížková and Bina, 2015). Stronger plate coupling limits trench mobility and can, when high enough, even preclude subduction (De Franco et al, 2006;Běhounková and Čížková, 2008;Androvičová et al, 2013) (Fig.…”

Thermomechanical models for the dynamics and melting processes in the Mariana subduction system

“…The statistical analysis and numerical models show that the stress state of the back-arc regions can be either extension or compression [e.g., Uyeda and Kanamori, 1979;Heuret and Lallemand, 2005;Heuret et al, 2007]. The deformation mode has been attributed to the plate kinematics, the properties of the downgoing slab, the effects of lateral mantle flow on the slab, and mantle wedge dynamics [e.g., Sdrolias and Müller, 2006;Arcay et al, 2008]. Far-field stresses resulting from continent-continent collision and changes of plate direction may also contribute to back-arc extension [e.g., Silver et al, 1998;Clark et al, 2008].…”