EGU24-6689, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Hoop Stresses in Free Subduction on a Sphere

Neil Ribe1, Stephanie Chaillat2, Gianluca Gerardi3, Alexander Chamolly4, and Zhonghai Li5
Neil Ribe et al.
  • 1Lab FAST, Universite Paris-Saclay, CNRS, Orsay, France (
  • 2Lab POems, ENSTA-UMA, Palaiseau, France
  • 3MINES ParisTech, PSL Research University, Fontainebleau, France
  • 4Institut Pasteur, Universite de Paris, CNRS, Paris, France
  • 5Key Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing, China

Because Earth's tectonic plates are doubly curved shells, their mechanical behavior during subduction can differ significantly from that of flat plates. We use the boundary-element method to study free (gravity-driven) subduction in 3-D spherical geometry. The model comprises a shell with thickness h and viscosity η1 subducting in a viscous planet with radius R0. Our focus is on the magnitude of the longitudinal normal membrane stress (`hoop stress'), which has no analog in Cartesian geometry. Scaling analysis based on thin-shell theory shows that the resultant (integral across the shell) of the hoop stress obeys the scaling law Tφ ∼ (η1h W/R0) max(1, cotθ) where θ is the colatitude and W is the velocity of the shell normal to its midsurface that is associated with bending. We find that the state of stress in the slab is dominated by the hoop stress, which is 3-7 times larger than the downdip stress. Because the hoop stress is compressive, it can drive longitudinal buckling instabilities. We perform a linear stability analysis of a subducting spherical shell to determine a scaling law for the most unstable wavelength, which we compare with observed shapes of trenches in the Pacific ocean. 

How to cite: Ribe, N., Chaillat, S., Gerardi, G., Chamolly, A., and Li, Z.: Hoop Stresses in Free Subduction on a Sphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6689,, 2024.