Science in China Series D: Earth Sciences

, Volume 51, Issue 12, pp 1683–1693 | Cite as

Seismic anisotropy of upper mantle in Sichuan and adjacent regions

Article
First Online:
Received:
Accepted:

Abstract

Based on the polarization analysis of teleseismic SKS waveform data recorded at 94 broadband seismic stations in Sichuan and adjacent regions, the SKS fast-wave direction and the delay time between the fast and slow shear waves were determined at each station using the grid searching method of minimum transverse energy and the stacking analysis method, and the image of upper mantle anisotropy was acquired. The fast-wave polarization directions are mainly NW-SE in the study area, NWW-SEE to its northeast and NS to its west. The delay time falls into the interval [0.47 s, 1.68 s]. The spatial variation of the fast-wave directions is similar to the variation of GPS velocity directions. The anisotropic image indicates that the regional tectonic stress field has resulted in deformation and flow of upper mantle material, and made the alignment of upper mantle peridotite lattice parallel to the direction of material deformation. The crust-upper mantle deformation in Sichuan and adjacent regions accords with the mode of vertically coherent deformation. In the eastern Tibetan Plateau, the crustal material was extruded to east or southeast due to SE traction force of the upper mantle material. The extrusion might be obstructed by a rigid block under the Sichuan Basin and the crust has been deformed. After a long-term accumulation of tectonic strain energy, the accumulative energy suddenly released in Yingxiu town of the Longmenshan region, and Wenchuan M S8.0 earthquake occurred.

Keywords

upper mantle anisotropy SKS wave fast-wave polarization direction lithospheric deformation Wenchuan MS8.0 earthquake 
This is a preview of subscription content, log in to check access.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Ren J S. The basic characteristics of the tectonic evolution of the continental lithosphere in China (in Chinese). Reg Geol China, 1991, 2: 289–293Google Scholar
  2. 2.
    Molnar P, Tapponnier P. Active tectonics of Tibet. J Geophys Res, 1978, 83: 5361–5376CrossRefGoogle Scholar
  3. 3.
    Royden L H, Burchfiel B C, King R W, et al. Surface deformation and lower crustal flow in eastern Tibet. Science, 1997, 276: 788–790CrossRefGoogle Scholar
  4. 4.
    Flesch M L, Holt W E, Silver P G, et al. Constraining the extent of crust-mantle coupling in central Asia using GPS, geologic, and shear wave splitting data. Earth Planet Sci Lett, 2005, 238: 248–268CrossRefGoogle Scholar
  5. 5.
    Silver P G. Seismic anisotropy beneath the continents: Probing the depths of geology. Ann Rev Earth Planet Sci, 1996, 24: 385–432CrossRefGoogle Scholar
  6. 6.
    Lev E, Long M D, van der Hilst R D. Seismic anisotropy in Eastern Tibet from shear wave splitting reveals changes in lithospheric deformation. Earth Planet Sci Lett, 2006, 251: 293–304CrossRefGoogle Scholar
  7. 7.
    Meissner R, Mooney W D, Artemieva I. Seismic anisotropy and mantle creep in young orogens. Geophysics, 2002, 149: 1–14Google Scholar
  8. 8.
    Gao Y, Zheng S H, Zhou H L. Polarization patterns of fast shear wave in Tangshan region and their variations (in Chinese). Chin J Geophys, 1999, 42(2): 228–232Google Scholar
  9. 9.
    Zheng X F, Chen C H, Zhang C H. Study on temporal variations of shear-wave splitting in the Chiayi area, aftershock zone of 1999 Chichi earthquake, Taiwan (in Chinese). Chin J Geophys, 2008, 51(1): 149–157Google Scholar
  10. 10.
    Silver P G, Chan W W. Share-wave splitting and subcontinental mantle deformation. J Geophys Res, 1991, 96: 16429–16454CrossRefGoogle Scholar
  11. 11.
    McNamara D, Owens T, Silver P G, et al. Shear-wave anisotropy beneath the Tibetan Plateau. J Geophys Res, 1994, 99: 13655–13665CrossRefGoogle Scholar
  12. 12.
    Ding Z F, Zeng R S. Observation and study of shear wave anisotropy in Tibetan Plateau (in Chinese). Chin J Geophys, 1996, 39(2): 211–219Google Scholar
  13. 13.
    Jiang M, Xu Z Q, Hirn A, et al. Teleseimic anisotropy and corresponding features of upper mantle in Tibetan Plateau and its neighboring areas (in Chinese). Acta Geosci Sin, 2001, 22(2): 111–116Google Scholar
  14. 14.
    Lü Q T, Ma K Y, Jiang M. Seismic anisotropy beneath Southern Tibet (in Chinese). Acta Seismol Sin, 1996, 18(2): 215–223Google Scholar
  15. 15.
    Chang L J, Wang C Y, Ding Z F. A study on SKS splitting beneath the Yunnan region (in Chinese). Chin J Geophys, 2006, 49: 197–204Google Scholar
  16. 16.
    Wang C Y, Chang L J, Lü Z Y, et al. Seismic anisotropy of upper mantle in eastern Tibetan Plateau and related crust-mantle coupling pattern. Sci China Ser D-Earth Sci, 2007, 50(8): 1150–1160CrossRefGoogle Scholar
  17. 17.
    Chang L J, Wang C Y, Ding Z F, et al. Seismic anisotropy of upper mantle in the northeastern margin of the Tibetan Plateau (in Chinese). Chin J Geophys, 2008, 51(2): 431–438Google Scholar
  18. 18.
    Vinnik L P, Farra V, Romanowicz B. Azimuthal anisotropy in the Earth from observations of SKS at Geoscope and NARS broadband stations. Bull Sesimol Soc Am, 1989, 79: 1452–1558Google Scholar
  19. 19.
    Wolfe C J, Silver P G. Seismic anisotropy of oceanic upper mantle: Shear wave splitting methodologies and observations. J Geophys Res, 1998, 103(B1): 749–771CrossRefGoogle Scholar
  20. 20.
    Wang C Y, Chan W W, Mooney W D. 3-D velocity structure of crust and upper mantle in southwestern China and its tectonic implications. J Geophys Res, 2003, 108 (B9): 2442, doi:10.1029/2002JB001973CrossRefGoogle Scholar
  21. 21.
    Zhang Z J, Bai Z M, Wang C Y, et al. The crustal structure under Sanjiang and its dynamic implications: Revealed by seismic reflection/refraction profiling between Zhefang and Binchuan,Yunnan. Sci China Ser D-Earth Sci, 2005, 48(9): 1329–1336CrossRefGoogle Scholar
  22. 22.
    Zhang Z J, Bai Z M, Wang C Y, et al. The crustal structure of Gondawana and Yangtze blocks: An example by wide angel seismic reflection profiling between Menglian and Malong. Sci China Ser D-Earth Sci, 2005, 48(11): 1828–1836CrossRefGoogle Scholar
  23. 23.
    Wang C Y, Lou H, Lu Z Y, et al. S wave crustal and upper mantle’s velocity structure in eastern Tibetan Plateau — Deep environment of low crustal flow. Sci China Ser D-Earth Sci, 2008, 51(2): 263–274CrossRefGoogle Scholar
  24. 24.
    Peng Y J, Huang Z X, Su W, et al. Anisotropy in crust and upper mantle beneath China continent and its adjacent seas (in Chinese). Chin J Geophys, 2007, 50(3): 752–759Google Scholar
  25. 25.
    An M, Shi Y. Lithospheric thickness of the Chinese continent. Phys Earth Planet Int, 2006, 159: 257–266CrossRefGoogle Scholar
  26. 26.
    Ding G Y. Lithospheric Dynamics of China (in Chinese). Beijing: Seismological Press, 1991Google Scholar
  27. 27.
    Gan W J, Zhang P Z, Shen Z K, et al. Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements. J Geophys Res, 2007, 112, B08416, doi:10.1029/2005JB004120CrossRefGoogle Scholar
  28. 28.
    Zhang P Z, Shen Z K, Wang M, et al. Continuous deformation of the Tibetan Plateau from global positioning system data. Geology, 2004, 32(9): 809–812CrossRefGoogle Scholar
  29. 29.
    Chen Z, Burchfiel B C, Liu Y, et al. Global Positioning System measurements from eastern Tibet and their implications for India/Eurasia intercontinental deformation. J Geophys Res, 2000, (105): 16215–16228Google Scholar
  30. 30.
    Teng J W, Zeng R S, Yan Y F, et al. The depth distribution of Moho and tectonic framework in eastern Asian continent and its adjacent ocean areas (in Chinese). Sci China Ser D-Earth Sci, 2002, 32(1): 89–100Google Scholar
  31. 31.
    Ma X Y. Map of Lithospheric Dynamics in China and the Vicinity (in Chinese). Beijing: Geological Publishing House, 1989Google Scholar
  32. 32.
    Xu Z H, Wang S Y, Huang Y R, et al. Directions of mean stress axes in southwestern China deduced from microearthquake data (in Chinese). Chin J Geophys, 1987, 30: 476–486Google Scholar
  33. 33.
    Li C, R D van der Hilst, Toks M N. Constraining P-wave velocity variations in the upper mantle beneath Southeast Asia. Phys Earth Planet Int, 2006, 154: 180–195CrossRefGoogle Scholar
  34. 34.
    Lou H, Wang C Y. Wavelet analysis and interpretation of gravity data in Sichuan-Yunnan region, China (in Chinese). Acta Seismol Sin, 2003, 27(5): 515–523Google Scholar
  35. 35.
    Wang C Y, Han W B, Wu J P. Crustal structure beneath the eastern margin of the Tibetan Plateau and its tectonic implications. J Geophys Res, 2007, 112, B07307, doi:10.1029/2005JB003873CrossRefGoogle Scholar

Copyright information

© Science in China Press and Springer-Verlag GmbH 2008

Authors and Affiliations

  1. 1.Institute of GeophysicsChina Earthquake AdministrationBeijingChina

Personalised recommendations