Advertisement

pure and applied geophysics

, Volume 138, Issue 3, pp 429–444 | Cite as

Love-Rayleigh wave incompatibility and possible deep upper mantle anisotropy in the Iberian peninsula

  • Valérie Maupin
  • Michel Cara
Article

Abstract

Love and Rayleigh wave phase velocities are analyzed with the goal of retrieving information about the anisotropic structure of the Iberian lithosphere. The cross-correlation method is used to measure the interstation phase velocities between diverse stations of the ILIHA network at periods between 20 and 120 s. Despite the 2-D structure of the network, the Love wave data are too few to enable an analysis of phase velocity azimuthal variations. Azimuthal averages of Love and Rayleigh wave phase velocities are calculated and inverted both in terms of isotropic and anisotropic structures. Realistic isotropic models explain the Rayleigh wave and short-period Love wave phase velocities. Therefore no significant anisotropy needs to be introduced in the crust and down to 100 km depth in the upper mantle to explain our data. A discrepancy is observed only at long periods, where the data are less reliable. Love wave data at periods between 80 and 120 s remain 0.15 km/s faster than predicted by isotropic models explaining the long-period Rayleigh wave data. Possibilities of biases in the measurements due to interferences with higher modes are examined but seem unlikely. A transversely isotropic model with 8% of S-wave velocity anisotropy in the upper mantle at depths larger than 100 km can explain the whole set of data. In terms of a classical model of mantle anisotropy, this corresponds to 100% of the crystals perfectly oriented in the horizontal plane in a pyrolitic mantle. This is a rather extreme model, which predicts at time delay between 0 and 2 seconds for split SKS.

Key words

Iberian Peninsula Love-Rayleigh discrepancy ILIHA anisotropy surface waves 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Aki, K., andKaminuma, K. (1963),Phase Velocity of Love Waves in Japan (Part 1): Love Waves from the Aleutian Shock of March 1957, Bull. Earthquake Res. Inst.41, 243–259.Google Scholar
  2. Anderson, D. L. (1961),Elastic Wave Propagation in Layered Anisotropic Media, J. Geophys. Res.66, 2953–2963.Google Scholar
  3. Anderson, D. L., andHarkrider, D. (1962),The Effect of Anisotropy on Continental and Oceanic Surface Wave Dispersion, J. Geophys. Res.76, 1627 (abstract).Google Scholar
  4. Ansel, V., andNataf, H. C. (1989),Anisotropy Beneath 9 Stations of the GEOSCOPE Broadband Network as Deduced from Shear-wave Splitting, Geophys. Res. Lett.16, 409–412.Google Scholar
  5. Babuska, V., andPlomerova, J. (1989),Seismic anisotropy of the subcrustal lithosphere in Europe: Another clue to recognition of accreted terranes? InDeep Structure and Past Kinematics of Accreted Terranes (ed. Hillhouse, J. W) Geophys. Monograph50, AGU, 209–217.Google Scholar
  6. Badal, J., Corchete, V., Payo, G., Canas, J. A., Pujades L., andSeron, F. J. (1990),Processing and Inversion of Long Period Surface Waves Data Collected in the Iberian Peninsula, Geophys. J.100, 193–202.Google Scholar
  7. Bamford, D. (1977),Pn Velocity Anisotropy in a Continental Upper Mantle, Geophys. J. R. Astr. Soc.49, 29–48.Google Scholar
  8. Bamford, D., Jentsch, M., andProdehl, C. (1979),Pn Anisotropy Studies in Northern Britain and the Eastern and Western United States, Geophys. J. R. Astr. Soc.57 397–429.Google Scholar
  9. Banda, E. (1988),Crustal Parameters in the Iberian Peninsula, Phys. Earth Planet. Int.51, 222–225.Google Scholar
  10. Banda, E., andAnsorge, J. (1980),Crustal Structure under the Central and Eastern Part of the Betic Cordillera, Geophys. J. R. Astr. Soc.63, 515–532.Google Scholar
  11. Cara, M. (1978),Etude du manteau supérieur à partir des harmoniques des ondes de surface, Thèse d'Etat, Université de Paris 6.Google Scholar
  12. Cara, M., andLévêque, J.-J. (1988),Anisotropy of the Asthenosphere: The Higher Mode Data of the Pacific Revisited, Geophys. Res. Lett.15, 205–208.Google Scholar
  13. Cara, M., Nercessian, A., andNolet, G. (1980),New Inferences from Higher Mode Data in Western Europe and Northern Eurasia, Geophys. J. R. Astr. Soc.61, 459–478.Google Scholar
  14. Dost, B. (1990),Upper Mantle Structure under Western Europe from Fundamental and Higher Mode Surface Waves Using the NARS Array, Geophys. J.100, 131–151.Google Scholar
  15. Dziewonski, A. M., Mills, J., andBloch, S. (1972),Residual Dispersion Measurement—A New Method of Surface Wave Analysis, Bull. Seismol. Soc. Am.62, 129–139.Google Scholar
  16. Estey, L. H., andDouglas, B. J. (1986),Upper Mantle Anisotropy: A Preliminary Model, J. Geophys. Res.91, 11,393–11,406.Google Scholar
  17. Fuchs, K. (1983),Recently Formed Elastic Anisotropy and Petrological Models for the Continental Suberustal Lithosphere in Southern Germany, Phys. Earth Planet. Int.31, 93–118.Google Scholar
  18. Gregersen, S. (1978),Possible Mode Conversion between Love and Rayleigh Waves at a Continental Margin, Geophys. J. R. Astr. Soc.54, 121–127.Google Scholar
  19. James, D. (1971),Anomalous Love Wave Phase Velocities, J. Geophys. Res.76, 2077–2083.Google Scholar
  20. Kawasaki, I., andKonn'o, F. (1984),Azimuthal Anisotropy of Surface Waves and the Possible Type of the Seismic Anisotropy due to Preferred Orientation of Olivine in the Uppermost Mantle Beneath the Pacific Ocean, J. Phys. Earth32, 229–244.Google Scholar
  21. Lévêque, J.-J., Cara, M., andRouland, D. (1991),Waveform Inversion of Surface Wave Data: Test of a New Tool for Systematic Investigation of Upper Mantle Structures, Geophys. J. Int.104, 565–581.Google Scholar
  22. McEvilly, T. V. (1964),Central. U.S. Crust-Upper Mantle Structure from Love and Rayleigh Wave Phase Velocity Inversion, Bull. Seismol. Soc. Am.54, 1997–2015.Google Scholar
  23. Montagner, J.-P., andNataf, H.-C. (1986),A Simple Method for Inverting the Azimuthal Anisotropy of Surface Waves, J. Geophys. Res.91, 511–520.Google Scholar
  24. Nishimura, C. E., andForsyth, D. W. (1988),Rayleigh Wave Phase Velocities in the Pacific with Implications for Azimuthal Anisotropy and Lateral Heterogeneities, Geophys. J.94, 479–501.Google Scholar
  25. Nishimura, C. E., andForsyth, D. W. (1989),The Anisotropic Structure of the Upper Mantle in the Pacific, Geophys. J.96, 203–229.Google Scholar
  26. Saito, M.,Disper 80: a subroutine package for the calculation of seismic modes solutions. InSeismological Algorithms (ed. Doornbos, D. J.) (Academic Press, New York 1988).Google Scholar
  27. Schlue, J. W., andKnopoff, L. (1977),Shear-wave Polarization Anisotropy in the Pacific Basin, Geophys. J. R. Astr. Soc.49, 145–165.Google Scholar
  28. Silver, P. G., andChan, W. W. (1988),Implications for Continental Structure and Evolution from Seismic Anisotropy, Nature335, 34–39.Google Scholar
  29. Surinach, E., andVegas, R. (1988),Lateral Inhomogeneities of the Hercynian Crust in Central Spain, Phys. Earth Planet. Int.51, 226–234.Google Scholar
  30. Takeuchi, H., andSaito, M.,Seismic surface waves. InMethods in Computational Physics, vol. 11, (Academic Press, New York 1972) pp. 217–295.Google Scholar
  31. Tarantola, A., andValette, B. (1982),Generalized Nonlinear Inverse Problems Solved Using the Least Squares Criterion, Rev. Geophys. Space Phys.20, 219–232.Google Scholar
  32. Vauchez, A., andNicolas, A. (1991),Mountain-building: Strike Parallel Motion and Mantle Anisotropy, Tectonophys.185, 183–201.Google Scholar
  33. Vinnik, L. P., Farra, V., andRomanowicz, B. (1989),Azimuthal Anisotropy in the Earth from Observations of SKS at GEOSCOPE and NARS Broadband Stations, Bull. Seismol. Soc. Am.79, 1542–1558.Google Scholar
  34. Wielandt, E., Sigg, A., Plesinger, A., andHoralek J. (1987),Deep Structure of the Bohemian Massif from Phase Velocities of Rayleigh and Love Waves, Studia Geoph. et Geod.31, 121–127.Google Scholar

Copyright information

© Birkhäuser Verlag 1992

Authors and Affiliations

  • Valérie Maupin
    • 1
  • Michel Cara
    • 1
  1. 1.Institut de Physique du Globe de StrasbourgStrasbourg CedexFrance

Personalised recommendations