1 / 25

ANISOTROPIC SEISMOLOGY IN ANTARCTICA

ANISOTROPIC SEISMOLOGY IN ANTARCTICA. Jean-Paul Montagner, Geneviève Roult and Eric Beucler Institut de Physique du Globe Université Paris VII-Denis Diderot. JEAN-PA. Importance of seismic anisotropy ANISOTROPY is the RULE not the Exception. Anisotropy is present at all scales.

dolph
Télécharger la présentation

ANISOTROPIC SEISMOLOGY IN ANTARCTICA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ANISOTROPIC SEISMOLOGY IN ANTARCTICA Jean-Paul Montagner, Geneviève Roult and Eric Beucler Institut de Physique du Globe Université Paris VII-Denis Diderot JEAN-PA

  2. Importance of seismic anisotropyANISOTROPY is the RULE not the Exception Anisotropy is present at all scales • From microscopic scale to macroscopic scale. • Efficient alignment mechanisms: • (L.P.O.: lattice preferred orientation • S.P.O.: shape preferred orientation; Fine layering)

  3. (From Christensen and Lundquist, 1982)

  4. Cracks, Fluid inclusions Crust Inner Core (Babuska and Cara, 1991) (Singh et al., 2001)

  5. Hot Cold Montagner &Guillot, 2001

  6. Da: Anisotropy Effect DT: Temperature Effect Olivine (60%) +Opx (40%) Da ≈ DT Montagner &Guillot, 2001

  7. Importance of seismic anisotropyANISOTROPY is the RULE not the Exception Anisotropy is present at all scales • From microscopic scale to macroscopic scale. • Efficient alignment mechanisms: • (L.P.O.: lattice preferred orientation • S.P.O.: shape preferred orientation; Fine layering) ANISOTROPY IS NOT A SECOND ORDER EFFECT ANISOTROPY IS REFLECTING AN INNER ORGANIZATION Anisotropy is observed on different kinds of seismic waves - Body waves (Pn, Shear wave splitting) - Surface waves (Rayleigh-Love discrepancy; Azimuthal anisotropy)

  8. SKS- Splitting > +SH If anis. core Transverse Mantle Radial Radial

  9. S-wave Splitting Measurements (Savage, Rev. Geophys., 1999)

  10. S- Velocity Radial Anisotropy Azimuthal Anisotropy Interpretation

  11. Paths of paths in block 5 x5º paths

  12. Sieminski & Lévêque, 2003

  13. Sieminski & Lévêque, 2003

  14. Radial Azimuthal reference

  15. Ridge Ridge Continent-ocean boundary

  16. CONCLUSIONS • Seismic anisotropy is not a second order effect. • Anisotropy is a good MARKER of deformation processes. • Antarctic Plate: • Continental shield root around 220km. • Azimuthal anisotropy large and orthogonal to ridges • Intense deformation from PAI triple junction up to Africa: shear zone, fossil or present anisotropy (reality or artefact?)

  17. Anisotropy- Geodynamics Relationship Gaboret et al., 2003

  18. Boundary layer => observable seismic anisotropy <===

  19. (Montagner and Guillot, 2001)

More Related