EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Quantifying the effective seismic anisotropy produced by a ridge-transform model 

Thomas Bodin1, Alexandre Janin2, Milena Marjanovic3, Cecile Prigent3, Yann Capdeville4, Sebastien Chevrot5, and Stephanie Durand1
Thomas Bodin et al.
  • 1Univ Lyon, Université Lyon 1, ENS de Lyon, CNRS, UMR 5276 LGL-TPE, F-69622, Villeurbanne, France (
  • 2Ecole Normale Supérieure, PSL Research University, CNRS UMR 8538
  • 3Institut de Physique du Globe de Paris, CNRS UMR 7154, Université Paris Diderot-Paris 7, Paris, France
  • 4Laboratoire de Planetologie et de Geodynamique, UMR CNRS 6112, Universite de Nantes, 44300 Nantes, France
  • 5GET, UMR 5563, Observatoire Midi Pyrenees, Universite Paul Sabatier, CNRS, IRD, Toulouse, France

Global tomographic models depict long-wavelength azimuthal anisotropy in the oceanic upper mantle, with a fast axis direction orthogonal to divergent plate boundaries. This anisotropy is usually attributed to the Lattice Preferred Orientation (LPO) of olivine due to asthenospheric mantle flow away from the ridge axis. In this work, we want to test an alternative hypothesis, whether this observed anisotropic signal could be partially explained by the presence of transform faults and associated fracture zones in the lithosphere. The transform plate boundaries represent sharp structures perpendicular to the ridge-axis with the wavelength (˜10 km), which is much smaller than the wavelength of seismic surface waves used to image the mantle (˜100 km). Therefore, transform faults could potentially result in an effective anisotropy in tomographic images through their Shape Preferred Orientation (SPO). We base our calculations on several thermo-chemical models that follow the observed ridge-transform geometry at different spreading rates. To produce the effective medium as seen by long-period waves, we use a non-periodic homogenization algorithm. The resulting seismic velocity field can be interpreted as the tomographic image that would be obtained after inverting long-period seismic data; it is smooth, fully anisotropic, and comparable to actual tomographic models.

How to cite: Bodin, T., Janin, A., Marjanovic, M., Prigent, C., Capdeville, Y., Chevrot, S., and Durand, S.: Quantifying the effective seismic anisotropy produced by a ridge-transform model , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10088,, 2022.