Advertisement

Journal of Seismology

, Volume 9, Issue 2, pp 211–222 | Cite as

Analysis of the seismicity in the central part of the Pyrenees (France), and tectonic implications

  • Alexis Rigo
  • Annie Souriau
  • Noalwenn Dubos
  • Matthieu Sylvander
  • Christian Ponsolles
Article

Abstract

Two temporary seismological networks have been set up in 2000 and 2002 in the central part of the Pyrenees, in a region, which appears as a transition between two domains where both the seismic activity and the tectonic regime are different. Together with the permanent networks, they allowed us to obtain precise hypocenter locations for more than 400 events with local magnitudes ranging from 1.5 to 4.6, as well as 30 new focal mechanisms. The seismicity is distributed in several clusters, which are not located along the North Pyrenean Fault, considered as the major tectonic accident resulting from the suture of the Iberian and Eurasian convergent plates when the range formed. Several small fault segments dipping to the north are identified. The maximum focal depth varies from 10 to 20 km, with variations which are roughly parallel to those of the Moho, indicating a thickening of the seismogenic layer to the east of the studied area. The obtained focal solutions reveal a predominance of normal faulting to the West and reverse faulting to the East, with strike-slip motions in between. The largest fault segment to the East, with a length of about 20 km, could possibly be related to a large historical event which occurred in 1660, with intensity IX, close to cities which have become since then important touristic centres.

Key Words

fault plane solutions hypocentre locations Lourdes Pyrenees seismological campaign stress tensor tectonics 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Beaumont, C., Munoz, J.A., Hamilton, J. and Fullsack, P., 2000, Factors controlling the Alpine evolution of the central Pyrenees inferred from a comparison of observations and geodynamical models, J. Geophys. Res. 105, 8121–8145.CrossRefGoogle Scholar
  2. BRGM, 1980, Carte géologique de la France 1/50000 – Argelès-Gazost, Ed. BRGM, Orléans, France.Google Scholar
  3. BRGM, 1996, Carte géologique de la France 1/50000 – Campan, Ed. BRGM, Orléans, France.Google Scholar
  4. Choukroune, P., 1992, Tectonic evolution of the Pyrenees, Annu. Rev. Earth Planet. Lett. 20, 143–158.CrossRefGoogle Scholar
  5. Choukroune, P. and Séguret, M., 1973, Carte structurale des Pyrénées, Ed. ELF-ERAP, Boussens, France.Google Scholar
  6. Daignières, M., Gallart, J. and Banda, E., 1981, Lateral variation of the crust in the North Pyrenean Zone, Ann. Géophys. 37, 435–456.Google Scholar
  7. Delouis, B., Haessler, H., Cisternas, A. and Rivera, L., 1993, Stress tensor determination in France and neighbouring regions, Tectonophysics 221, 413–437.CrossRefGoogle Scholar
  8. Dubos, N., 2003, Contribution à l’évaluation du risque sismique dans les Pyrénées, Ph.D. Thesis, Univ. Paul Sabatier, Toulouse, France.Google Scholar
  9. Dubos, N., Souriau, A., Ponsolles, C., Fels, J.-F. and Sénéchal, G., 2003, Etudes des effets de sites dans la ville de Lourdes (Pyrénées, France) par la méthode des rapports spectraux, Bull. Soc. géol. Fr. 174, 33–44.CrossRefGoogle Scholar
  10. Dubos, N., Sylvander, M., Souriau, A., Ponsolles, C., Chevrot, S., Fels, J.-F. and Benahmed, S., 2004, Analysis of the May 2002 earthquake sequence in Central Pyrenees, Consequences for the evaluation of the seismic risk at Lourdes, France, Geophys. J. Int. 156, 527–540.CrossRefGoogle Scholar
  11. Gagnepain-Beyneix, J., Haessler, H. and Modiano, T., 1982, The Pyrenean earthquake of February 29, 1980: An example of complex faulting, Tectonophysics 85, 273–290.CrossRefGoogle Scholar
  12. Gagnepain-Beyneix, J., 1987, Étude expérimentale des tremblements de terre. Exemple de la région d’Arette (France), Thesis, Université Paris 6, France.Google Scholar
  13. Gallart, J., Banda, E. and Daignères, M., 1981, Crustal structure of the Paleozoic Axial Zone of the Pyrenees and transition to the North Pyrenean Zone, Ann. Geophys. 37, 457–480.Google Scholar
  14. Hirn, A., Daignières, M., Gallart, J. and Vadell, M., 1980, Explosion seismic sounding of throws and dips in the continental moho, Geophys. Res. Lett. 7, 263–266.Google Scholar
  15. Lambert, J. and Levret-Albaret, A., 1996, Mille ans de séismes en France, 78 pp., BRGM, Nantes.Google Scholar
  16. Lee, W.H.K. and Lahr, J.C., 1975, HYPO71 (revised): A computer program for determining hypocenter, magnitude and first motion pattern of local earthquakes, pp. 116, U.S. Geol. Survey Open-File report.Google Scholar
  17. Levet, S., Toutain, J.-P., Munoz, M., Pinaud, J.-L., Sylvander, M., Rigo, A. and Escalier, J., 2003, Modelling the mixing function to constrain co-seismic hydrochemical effects: An example from french Pyrenees, Pageoph, submitted.Google Scholar
  18. Levret, A., Cushing, M. and Peyridieu, G., 1995, Etude des caractéristiques de séismes historiques en France: atlas de 140 cartes macrosismiques, Publ. Inst. Protection Sureté Nucléaire, Fontenay-aux-Roses, France.Google Scholar
  19. Nicolas, M., Santoire, J.-P. and Delpech, P.-Y., 1990, Intraplate seismicity: New seismotectonic data in western Europe, Tectonophysics 179, 27–53.CrossRefGoogle Scholar
  20. Njike-Kassala, J.-D., Souriau, A., Gagnepain-Beyneix, J., Martel, L. and Vadell, M., 1992, Frequency-magnitude relationship and Poisson’s ratio in the Pyrenees, in relation to earthquake distribution, Tectonophysics 215, 363–369.CrossRefGoogle Scholar
  21. Poitrasson, F., Dundas, S., Toutain, J.-P., Munoz, M. and Rigo, A., 1999, Earthquake-related elemental and isotopic lead anomaly in a springwater, Earth Planet. Sci. Lett. 169, 269–276.CrossRefGoogle Scholar
  22. Puigdefabregas, C. and Souquet, P., 1986, Tecto-sedimentary cycles and depositional sequences of the Mesozoic and Tertiary from the Pyrenees, Tectonophysics 129, 173–203.CrossRefGoogle Scholar
  23. Rigo, A., Pauchet, H., Souriau, A., Grésillaud, A., Nicolas, M., Olivera, C. and Figueras, S., 1997, The February 1996 earthquake sequence in the eastern Pyrenees: First results, J. Seismology 1, 3–14.CrossRefGoogle Scholar
  24. Rivera, L. and Cisternas, A., 1990, Stress tensor and fault plane solutions for a population of earthquakes, Bull. Seism. Soc. Am. 80, 600–614.Google Scholar
  25. Souriau, A. and Granet, M., 1995, A tomographic study of the lithosphere beneath the Pyrenees from local and teleseismic data, J. Geophys. Res. 100, 18,117–18,134.Google Scholar
  26. Souriau, A. and Pauchet, H., 1998, A new synthesis of Pyrenean seismicity and its tectonic implications, Tectonophysics 290, 221–244.CrossRefGoogle Scholar
  27. Souriau, A., Sylvander, M., Rigo, A., Fels, J.-F., Douchain, J.-M. and Ponsolles, C., 2001, Sismotectonique des Pyrénées: Principales contraintes sismologiques, Bull. Soc. géol. France 172, 25–39.CrossRefGoogle Scholar
  28. Sylvander, M., 1999, Identifying an asperity through 3-D mapping of the frequency-magnitude distribution, Geophys. Res. Lett. 26, 2657–2660.CrossRefGoogle Scholar
  29. Toutain, J.P., Munoz, M., Poitrasson, F. and Lienard, A.C., 1997, Springwater chloride ion anomaly prior to a ML = 5.2 Pyrenean earthquake, Earth Planet. Sci. Lett. 149, 113–119.CrossRefGoogle Scholar
  30. Vacher, P. and Souriau, A., 2001, A three-dimensional model of the Pyrenean deep structure based on gravity modelling, seismic images and petrological constraints, Geophys. J. Int. 145, 460–470.CrossRefGoogle Scholar

Copyright information

© Springer Science + Business Media, Inc. 2005

Authors and Affiliations

  • Alexis Rigo
    • 1
  • Annie Souriau
    • 1
  • Noalwenn Dubos
    • 1
  • Matthieu Sylvander
    • 1
  • Christian Ponsolles
    • 2
  1. 1.Observatoire Midi-PyrénéesCNRS/UPS UMR 5562ToulouseFrance
  2. 2.Observatoire Midi-PyrénéesCNRS/UPS UMR 5562TarbesFrance

Personalised recommendations