EGU2020-21869
https://doi.org/10.5194/egusphere-egu2020-21869
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The coupling transition depth in subduction zones: rheologically controlled and not constant

Ben Maunder1, Saskia Goes2, and Jeroen van Hunen3
Ben Maunder et al.
  • 1Imperial College London, South Kensington, United Kingdom (b.maunder@imperial.ac.uk)
  • 2Imperial College London, South Kensington, United Kingdom (s.goes@imperial.ac.uk)
  • 3Durham University, Durham, United Kingdom (jeroen.van-hunen@durham.ac.uk)

The subduction zone coupling transition depth, CTD, marks the transition from frictional/ductile decoupling between the two plates to viscous coupling between the subducting plate and convecting mantle. This depth plays an important role in the state of stress, earthquake potential, and the location of the volcanic arc. Based on previous studies of heat flow and seismic structure of circum-Pacific subduction zones, the CTD has been inferred to at a constant 70-80 km. The mechanism for this constancy remains elusive, although models have reproduced the sharpness of the CTD as a consequence of the evolving strength contrast between a frictional (damage) type rheology along the interface and temperature and stress dependent viscosity in the plates and mantle . Using kinematically driven subduction models with such rheology, we find a relationship between the CTD, slab age and velocity that predicts that 91 % of Pacific subduction zones should have an CTD between 65 and 80 km depth, consistent with observations. However, some other zones are predicted to have significantly deeper or shallower CTD.  For example, a 120 km CTD recently found in the Lesser Antilles can be explained by our models . Sub-arc slab depth is bound by a similar age-velocity relation to that derived for the CTD, but offset to ~50 km larger depths. Hence rheology exerts the primary control on the CTD, and the coupling transition depth is in fact not constant but varies with plate age and convergence.

How to cite: Maunder, B., Goes, S., and van Hunen, J.: The coupling transition depth in subduction zones: rheologically controlled and not constant, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21869, https://doi.org/10.5194/egusphere-egu2020-21869, 2020

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