Slab dip, surface tectonics: How and when do they change following an acceleration/slow down of the overriding plate?

• Published in: Tectonophysics 2018-02, Vol.726, p.110-120
• Main Authors: Guillaume, Benjamin, Hertgen, Solenn, Martinod, Joseph, Cerpa, Nestor G.
• Format: Article
• Language: English
• Subjects: Analogue modeling; Boundary conditions; Computer simulation; Convergence; Deformation; Earth Sciences; Evolution; Lithosphere; Mechanical properties; Ocean models; Oceans; Plate deformation; Plate tectonics; Sciences of the Universe; Slab dip; Steady state models; Subduction; Subduction (geology); Subduction zones; Tectonics; Transient subduction; Upper plate velocity; Velocity
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2018.01.030

We present analogue models simulating the subduction of an oceanic lithosphere beneath an overriding plate advancing at variable rates. The convergence velocity is imposed by lateral boundary conditions in this experimental set. We analyze the geometry of the slab and the deformation of the overriding plate. Experiments confirm the strong correlation between the absolute velocity of the overriding plate on the one hand, the geometry of the subducting plate and the deformation of the overriding plate on the other hand. Following an instantaneous change in kinematic boundary conditions, the subduction system progressively shifts to a new steady-state regime. Models suggest that the adjustment time necessary to shift from the previous to the new equilibrium is independent of the imposed upper plate velocity. Transient stage lasts ∼ 12.5 ± 6 m.y. for the shallow slab dip (100–150-km depth), ∼ 29.2 ± 10 m.y. for the deeper slab dip (300–350-km depth), and ∼ 2.2 ± 2 m.y. for the upper plate deformation. The analysis of present-day subduction zones and their evolution through the last 20 m.y suggests an adjustment time of ∼15 m.y. for shallow slab dip and ∼20 m.y. for deep slab dip in Nature. Since only few subduction zones have shown a constant upper plate velocity over the last 15 m.y., it suggests that most of them are in a transient stage at present-day. •Upper plate absolute velocity changes exert a first-order control on slab dip and overriding plate deformation regime.•Transient stage that results from changes in upper plate velocity lasts on average 2 m.y. for upper plate deformation, 12.5 m.y. for slab dip at 100-150 km-depth and 30 m.y. for slab dip at 300-350 km-depth and are independent of the absolute velocity of the upper plate.•Analysis of present-day subduction zones suggests an adjustment time of 15 m.y. for shallow slab dip (0-125 km-depth) and 20 m.y. for deeper slab dip (> 125 km-depth).