Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Complex and variable crustal and uppermost mantle seismic anisotropy in the western United States

Abstract

The orientation and depth of deformation in the Earth is characterized by seismic anisotropy1—variations in the speed of passing waves caused by the alignment of minerals under strain into a preferred orientation. Seismic anisotropy in the western US has been well studied2,3,4,5,6,7,8,9,10,11 and anisotropy in the asthenosphere is thought to be controlled by plate motions and subduction6,7,8,9. However, anisotropy within the crust and upper mantle and the variation of anisotropy with depth are poorly constrained. Here, we present a three-dimensional model of crustal and upper mantle anisotropy based on new observations of ambient noise12 and earthquake13 data that reconciles surface wave and body wave9 data sets. We confirm that anisotropy in the asthenosphere reflects a mantle flow field controlled by a combination of North American plate motion and the subduction of the Juan de Fuca and Farallon slab systems6,7,8,9. We also find that seismic anisotropy in the upper mantle and crust are largely uncorrelated: patterns of anisotropy in the crust correlate with geological provinces, whereas anisotropy in the upper mantle is controlled by temperature variations. We conclude that any coupling between anisotropy in the crust and mantle must be extremely complex and variable.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Major tectonic setting and examples of 2-psi azimuthal anisotropy for Rayleigh waves.
Figure 2: Example azimuthal anisotropy variation and dispersion in the study region.
Figure 3: Azimuthal anisotropy in the crust, uppermost mantle, and asthenosphere and predicted SKS splitting.
Figure 4: Comparison of predicted and observed SKS splitting and comparison of anisotropy between different layers.

References

  1. Savage, M. K. Seismic anisotropy and mantle deformation: What have we learned from shear wave splitting? Rev. Geophys. 37, 65–106 (1999).

    Article  Google Scholar 

  2. Ozalaybey, S. & Savage, M. K. Shear-wave splitting beneath western United States in relation to plate tectonics. J. Geophys. Res. 100, 18135–18149 (1995).

    Article  Google Scholar 

  3. Savage, M. K. & Sheehan, A. F. Seismic anisotropy and mantle flow from the Great Basin to the Great Plains, western United States. J. Geophys. Res. 105, 13715–13734 (2000).

    Article  Google Scholar 

  4. Silver, P. & Holt, W. The mantle flow field beneath western North America. Science 295, 1054–1057 (2002).

    Article  Google Scholar 

  5. Savage, M. K. Seismic anisotropy and mantle deformation in the western United States and southwestern Canada. Int. Geol. Rev. 44, 913–937 (2002).

    Article  Google Scholar 

  6. Becker, T. W., Schulte-Pelkum, V., Blackman, D. K., Kellogg, J. B. & O’Connell, R. J. Mantle flow under the western United States from shear wave splitting. Earth Planet. Sci. Lett. 247, 235–251 (2006).

    Article  Google Scholar 

  7. Marone, F. & Romanowicz, B. The depth distribution of azimuthal anisotropy in the continental upper mantle. Nature 447, 198–201 (2007).

    Article  Google Scholar 

  8. Zandt, G. & Humphreys, E. Toroidal mantle flow through the western US slab window. Geology 36, 295–298 (2008).

    Article  Google Scholar 

  9. West, J. D., Fouch, M. J., Roth, J. B. & Elkins-Tanton, L. T. Vertical mantle flow associated with a lithospheric drip beneath the Great Basin. Nature Geosci. 2, 438–443 (2009).

    Google Scholar 

  10. Moschetti, M. P., Ritzwoller, M. H., Lin, F. & Yang, Y. Seismic evidence for widespread western-US deep-crustal deformation caused by extension. Nature 464, 885–889 (2010).

    Article  Google Scholar 

  11. Buehler, J. S. & Shearer, P. M. Pn tomography of the western United States using USArray. J. Geophys. Res. 115, B09315 (2010).

    Article  Google Scholar 

  12. Lin, F., Moschetti, M. P. & Ritzwoller, M. H. Surface wave tomography of the western United States from ambient seismic noise: Rayleigh and Love wave phase velocity maps. Geophys. J. Int. 173, 281–298 (2008).

    Article  Google Scholar 

  13. Yang, Y., Ritzwoller, M. H., Lin, F., Moschetti, M. P. & Shapiro, N. M. Structure of the crust and uppermost mantle beneath the western United States revealed by ambient noise and earthquake tomography. J. Geophys. Res. 113, B12310 (2008).

    Article  Google Scholar 

  14. Sabra, K. G., Gerstoft, P., Roux, P., Kuperman, W. A. & Fehler, M. C. Surface wave tomography from microseisms in Southern California. Geophys. Res. Lett. 32, L14311 (2005).

    Article  Google Scholar 

  15. Shapiro, N. M., Campillo, M., Stehly, L. & Ritzwoller, M. H. High-resolution surface-wave tomography from ambient seismic noise. Science 307, 1615–1618 (2005).

    Article  Google Scholar 

  16. Pollitz, F. F. Observations and interpretation of fundamental mode Rayleigh wavefields recorded by the Transportable Array (USArray). J. Geophys. Res. 113, B10311 (2008).

    Article  Google Scholar 

  17. Lin, F., Ritzwoller, M. H. & Snieder, R. Eikonal tomography: Surface wave tomography by phase front tracking across a regional broad-band seismic array. Geophys. J. Int. 177, 1091–1110 (2009).

    Article  Google Scholar 

  18. Bensen, G. D. et al. Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements. Geophys. J. Int. 169, 1239–1260 (2007).

    Article  Google Scholar 

  19. Smith, M. L. & Dahlen, F. A. Azimuthal dependence of Love and Rayleigh-wave propagation in a slightly anisotropic medium. J. Geophys. Res. 78, 3321–3333 (1973).

    Article  Google Scholar 

  20. Barruol, G. & Kern, H. Seismic anisotropy and shear-wave splitting in lower-crustal and upper-mantle rocks from the Ivrea zone—experimental and calculated data. Phys. Earth Planet. Inter. 95, 175–194 (1996).

    Article  Google Scholar 

  21. Montagner, J-P. & Nataf, H-C. A simple method for inverting the azimuthal anisotropy of surface waves. J. Geophys. Res. 91, 511–520 (1986).

    Article  Google Scholar 

  22. Rumpker, G. & Silver, P. G. Apparent shear-wave splitting parameters in the presence of vertically varying anisotropy. Geophys. J. Int. 135, 790–800 (1998).

    Article  Google Scholar 

  23. Montagner, J-P., Griot-Pommera, D-A. & Lavé, J. How to relate body wave and surface wave anisotropy? J. Geophys. Res. 105, 19015–19027 (2000).

    Article  Google Scholar 

  24. Gripp, A. E. & Gordon, R. G. Young tracks of hotspots and current plate velocities. Geophys. J. Int. 150, 321–361 (2002).

    Article  Google Scholar 

  25. Zhang, S. Q. & Karato, S. Lattice preferred orientation of olivine aggregates deformed in simple shear. Nature 375, 774–777 (1995).

    Article  Google Scholar 

  26. Holt, W. E. Correlated crust and mantle strain fields in Tibet. Geology 28, 67–70 (2000).

    Article  Google Scholar 

Download references

Acknowledgements

Instruments [data] used in this study were made available through EarthScope (http://www.earthscope.org; EAR-0323309), supported by the National Science Foundation. The facilities of the IRIS Data Management System, and specifically the IRIS Data Management Center, were used for access to waveform and metadata required in this study. The IRIS DMS is funded through the National Science Foundation and specifically the GEO Directorate through the Instrumentation and Facilities Program of the National Science Foundation under Cooperative Agreement EAR-0552316. This work has been supported by NSF grants EAR-0711526 and EAR-0844097.

Author information

Authors and Affiliations

Authors

Contributions

F-C.L. carried out ambient noise and earthquake tomography for the Rayleigh-wave measurements, computed the three-dimensional inversion and co-wrote the paper. M.H.R. guided the study and co-wrote the paper. Y.Y. and M.P.M contributed surface-wave analysis tools. M.J.F. assembled and carried out SKS splitting measurements. All authors discussed the results and provided comments on the manuscript.

Corresponding author

Correspondence to Fan-Chi Lin.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 2546 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Lin, FC., Ritzwoller, M., Yang, Y. et al. Complex and variable crustal and uppermost mantle seismic anisotropy in the western United States. Nature Geosci 4, 55–61 (2011). https://doi.org/10.1038/ngeo1036

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/ngeo1036

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing