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pure and applied geophysics

, Volume 132, Issue 1–2, pp 1–19 | Cite as

Propagation and attenuation characteristics of the crustal phaseLg

  • Michel Campillo
Article

Abstract

TheLg wave consists of the superposition ofS waves supercritically reflected, and thus trapped, in the crust. This mode of propagation explains the strong amplitude of this phase and the large distance range in which it is observed. The numerical simulation leads to successful comparison between observed seismograms in stable continental areas and synthetics computed for simple standard crustal models. In regions with strong lateral variations, the influence of large-scale heterogeneities on theLg amplitude is not yet clearly established in terms of the geometrical characteristics of the crustal structure.

The analysis of the decay of amplitude ofLg with epicentral distance allows the evaluation of the quality factor ofS waves in the crust. The results obtained show the same trends as codaQ: a clear correlation with the tectonic activity of the region considered, both for the value ofQ at 1 Hz and for its frequency dependence, suggesting that scattering plays a prominent part among the processes that cause the attenuation.

The coda ofLg is made up of scatteredS waves. The study of the spatial attenuation of the coda indicated that a large part of the arrivals that compose the coda propagate asLg. The relative amplitude of the coda is larger at sites located on sediments because, in these conditions, a part ofLg energy can be converted locally into lower order surface modes.

Key words

Regional seismograms attenuation coda crustal structure surface waves 

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References

  1. Aki, K. (1980),Attenuation of Shear Waves in the Lithosphere for Frequencies from 0.05 to 25 Hz, Phys. Earth Planet. Interiors21, 50–60.Google Scholar
  2. Aki, K. (1982),Scattering and Attenuation, Bull. Seismol. Soc. Am.72, S319-S330.Google Scholar
  3. Baker, B. W., Der, Z. A., andMrazek, C. P. (1981),The Effect of Crustal Structure on the Regional Phases Pg and Lg at the Nevada Test Site, J. Geophys. Res.86, 1686–1700.Google Scholar
  4. Bard, P. Y., andBouchon, M. (1980a),The Seismic Response of Sediment Filled Valleys. Part 1: The Case of Incident SH Waves, Bull. Seismol. Soc. Am.70, 1263–1286.Google Scholar
  5. Bard, P. Y., andBouchon, M. (1980b),The Seismic Response of Sediment Filled Valleys. Part 2: The Case of Incident P and SV Waves, Bull. Seismol. Soc. Am.70, 1921–1941.Google Scholar
  6. Båth, M. (1954),The Elastic Waves Rg and Lg Along Eurasiatic Paths, Arkiv Geofysic2, 295–342.Google Scholar
  7. Bollinger, G. A. (1979),Attenuation of the Lg Phase and the Determination of mb in the Southeastern United States, Bull. Seismol. Soc. Am.69, 45–63.Google Scholar
  8. Bouchon, M. (1981),A Simple Method to Calculate Green's Functions for Elastic Layered Media, Bull. Seismol. Soc. Am.71, 959–971.Google Scholar
  9. Bouchon, M. (1982),The Complete Synthesis of Seismic Crustal Phases at Regional Distances, J. Geophys. Res.87, 1735–1741.Google Scholar
  10. Campillo, M., andBouchon, M. (1985),Synthetic SH Seismograms in a Laterally Varying Medium by the Discrete Wavenumber Method, Geophys. J. Roy. Astr. Soc.83, 307–317.Google Scholar
  11. Campillo, M. (1987),Lg Wave Propagation in a Laterally Varying Crust and the Spatial Distribution of the Quality Factor in Central France, J. Geophys. Res.92, 12604–12614.Google Scholar
  12. Campillo, M., Bouchon, M., andMassinon, B. (1984),Theoretical Study of the Excitation, Spectral Characteristics and Geometrical Attenuation of Regional Seismic Phases, Bull. Seismol. Soc. Am.74, 79–90.Google Scholar
  13. Campillo, M., Plantet, J. L., andBouchon, M. (1985),Frequency-dependent Attenuation in the Crust Beneath Central France from Lg Waves: Data Analysis and Numerical Modeling, Bull. Seismol. Soc. Am.75, 1395–1411.Google Scholar
  14. Cara, M., Minster J. B., andLeBras, R. (1981),Multimode Analysis of Rayleigh-type Lg. Part II. Application to Southern California and the Northwestern Sierra Nevada, Bull. Seismol. Soc. Am.71, 985–1002.Google Scholar
  15. Chavez, D. E., andPriestley, K. K. (1986),Measurement of Frequency-dependent Lg Attenuation in the Great Basin, Geophys. Res. Lett.13, 551–554.Google Scholar
  16. Chinn, D., Isacks, B., andBarazangi, M. (1980),High-frequency Seismic Wave Propagation in Western South America Along the Continental Margin, in the Nazca Plate and Across the Altiplano, Geophys. J. Roy. Astr. Soc.60, 209–244.Google Scholar
  17. Der, Z. A., Marshall, M. E., O'Donnell, A., andMcElfresh, T. W. (1984),Spatial Coherence and Attenuation of the Lg Phase and the Interpretation of Lg Coda, Bull. Seismol. Soc. Am.74, 1125–1147.Google Scholar
  18. Dwyer, J. J., Herrmann, R. B., andNuttli, O. W. (1983),Spatial Attenuation of the Lg Wave in the Central United States, Bull. Seismol. Soc. Am.73, 781–796.Google Scholar
  19. Espinosa, A. F. (1984),Lg-wave Attenuation in Contiguous United States (abs), EOS Transactions AGU65, 233.Google Scholar
  20. Gregersen, S. (1984),Lg-wave Propagation and Crustal Structure Differences in Denmark and the North Sea, Geophys. J. Roy. Astr. Soc.79, 217–234.Google Scholar
  21. Gutenberg, B. (1951),Revised Travel Times in Southern California, Bull. Seismol. Soc. Am.41, 143–164.Google Scholar
  22. Gutenberg, B. (1955),Channel Waves in the Earth's Crust, Geophysics20, 283–294.Google Scholar
  23. Hasegawa, H. S. (1985),Attenuation of Lg Waves in the Canadian Shield, Bull. Seismol. Soc. Am.75, 1569–1582.Google Scholar
  24. Herraiz, M., andEspinosa, A. F. (1986),Scattering and Attenuation of High Frequency Seismic Waves: Development of the Theory of Coda Waves, U.S.G.S. Open File Report 86-455.Google Scholar
  25. Herrmann, R. B. (1980),Q Estimates Using the Coda of Local Earthquakes, Bull. Seismol. Soc. Am.70, 447–468.Google Scholar
  26. Herrmann, R. B., andKijko A. (1983),Modelling Some Empirical Vertical Component Lg Relations, Bull. Seismol. Soc. Am.73, 157–171.Google Scholar
  27. Jones, F. B., Long, L. T., andMcKee, J. H. (1977),Study of the Attenuation and Azimuthal Dependence of Seismic Wave Propagation in the Southeastern United States, Bull. Seismol. Soc. Am67, 1503–1513.Google Scholar
  28. Kadinsky-Cade, K., Barazangi, M., Oliver, J., andIsacks, B. (1981),Lateral Variations of High-frequency Seismic Wave Propagation at Regional Distances Across the Turkish and Iranian Plateaus, J. Geophys. Res.86, 9377–9396.Google Scholar
  29. Kennett, B. L. N. (1984),Guided Wave Propagation in Laterally Varying Media I: Theoretical Developments, Geophys. J. Astr. Soc.79, 235–255.Google Scholar
  30. Kennett, B. L. N., andMykkeltveit, S. (1984),Guided Wave Propagation in Laterally Varying Media II. Lg Waves in Northwestern Europe, Geophys. J. Roy. Astr. Soc.79, 257–267.Google Scholar
  31. Kennett, B. L. N., Gregersen, S., Mykkeltveit, S., andNewmark, R. (1985),Mapping of Crustal Heterogeneity in the North Sea Basin via the Propagation of Lg Waves, Geophys. J. Roy. Astr. Soc.83, 299–306.Google Scholar
  32. Kim, W. Y. (1987),Modeling Short-period Crustal Phases at Regional Distances for the Seismic Source Parameter Inversion, Phys. Earth Planet. Interiors47, 159–178.Google Scholar
  33. Kind, R. (1978),The Reflectivity Method for a Buried Source, J. Geophysics44, 603–612.Google Scholar
  34. Knopoff, L., Schwab, F., andKausel, E. (1973),Interpretation of Lg, Geophys. J.33, 398–404.Google Scholar
  35. Kovach, R. L., andAnderson, D. L. (1964),Higher Mode Surface Waves and their Bearing on the Structure of the Earth's Mantle, Bull. Seismol. Soc. Am.54, 162–182.Google Scholar
  36. Lehmann, I. (1953),On the Short-period Surface Wave “Lg” and Crustal Structure, Bull. d'Information de l'UGGI2, 248–251.Google Scholar
  37. Mitchell, B. J. (1980),Frequency Dependence of Shear Wave Internal Friction in the Continental Crust of Eastern North America, J. Geophys. Res.85, 5212–5218.Google Scholar
  38. Ni, J., andBarazangi, M. (1983),High-frequency Seismic Wave Propagation Beneath the Indian Shield, Himalayan Arc, Tibetan Plateau and Surrounding Regions: High Uppermost Mantle Velocities and Efficient Sn Propagation Beneath Tibet, Geophys. J. Roy. Astr. Soc.72, 665–689.Google Scholar
  39. Nicolas, M., Massinon, B., Mechler, P., andBouchon, M. (1982),Attenuation of Regional Phases in Western Europe, Bull. Seismol. Soc. Am.72, 2089–2106.Google Scholar
  40. Nuttli, O. W. (1973),Seismic Wave Attenuation and Magnitude Relations for Eastern North America, J. Geophys. Res.78, 876–885.Google Scholar
  41. Nuttli, O. W. (1980),The Excitation and Attenuation of Seismic Crustal Phases in Iran, Bull. Seismol. Soc. Am.70, 469–485.Google Scholar
  42. Nuttli, O. W. (1981),On the Attenuation of Lg Waves in Western and Central Asia and their Use as a Discriminant between Earthquakes and Explosions, Bull. Seismol. Soc. Am.71, 249–261.Google Scholar
  43. Nuttli, O. W. (1982),The Earthquake Problem in the Eastern United States, ASCE J. Struct. Div.108, 1302–1312.Google Scholar
  44. Nuttli, O. W. (1986),Yield Estimates of Nevada Test Site Explosions Obtained from Seismic Lg Waves, J. Geophys. Res.91, 2137–2151.Google Scholar
  45. Oliver, J., andEwing, M. (1957),Higher Modes of Continental Rayleigh Waves, Bull. Seismol. Soc. Am.47, 187–204.Google Scholar
  46. Oliver, J., andEwing, M. (1958),Normal Modes of Continental Surface Waves, Bull. Seismol. Soc. Am.48, 33–49.Google Scholar
  47. Olsen, K. H., Braile, L. W., andStewart, J. N. (1983),Modeling Short-Period Crustal Phases (Pg-Lg) for Long-range Refraction Profiles, Phys. Earth Planet. Interiors31, 334–347.Google Scholar
  48. Panza, G. F., andCalcagnile, G. (1975),Lg, Li and Rg from Rayleigh Modes, Geophys. J.40, 475–487.Google Scholar
  49. Peseckis, L. L., andPomeroy, P. W. (1984),Estimation of Q Using Lg Waves and its Implications for Nuclear Estimations (abs.), EOS Transactions AGU65, 995.Google Scholar
  50. Press, F., andEwing, M. (1952),Two Slow Surface Waves Across North America, Bull. Seismol. Soc. Am.42, 219–228.Google Scholar
  51. Ruzaikin, A. I., Nersesov, I. L., Khalturin, V. I., andMolnar, P. (1977),Propagation of Lg and Lateral Variations of Crustal Structure in Asia, J. Geophys. Res.82, 307–316.Google Scholar
  52. Singh, S. K., andHerrmann, R. B. (1983),Regionalization of Crustal Coda Q in the Continental United States, J. Geophys. Res.88, 527–538.Google Scholar
  53. Street, R. L. (1976),Scaling Northeastern United States/Southeastern Canadian Earthquakes by their Lg Waves, Bull. Seismol. Soc. Am.66, 1525–1537.Google Scholar
  54. Wang, C. Y., andHerrmann, R. B. (1984),Modeling Lg Codes by P-SV and SH by Vertical Boundaries (abs.), EOS Transactions AGU65, 233.Google Scholar
  55. Wang, C. Y. (1981),Wave Theory for Seismograms Synthesis, Ph.D. Dissertation, Saint Louis University, Saint Louis, Missouri, USA.Google Scholar
  56. Wu, R.-S., andAki, K. (1985),Scattering of Elastic Waves by a Random Medium and the Small-scale Heterogeneities in the Lithosphere, J. Geophys. Res.90, 10261–10276.Google Scholar

Copyright information

© Birkhäuser Verlag 1990

Authors and Affiliations

  • Michel Campillo
    • 1
  1. 1.Observatoire de GrenobleUA CNRS 733, IRIGMGrenobleFrance

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