Letter | Published:

Western US intermountain seismicity caused by changes in upper mantle flow

Nature volume 524, pages 458461 (27 August 2015) | Download Citation

Abstract

Understanding the causes of intraplate earthquakes is challenging, as it requires extending plate tectonic theory to the dynamics of continental deformation. Seismicity in the western United States away from the plate boundary is clustered along a meandering, north–south trending ‘intermountain’ belt1. This zone coincides with a transition from thin, actively deforming to thicker, less tectonically active crust and lithosphere. Although such structural gradients have been invoked to explain seismicity localization2,3, the underlying cause of seismicity remains unclear. Here we show results from improved mantle flow models that reveal a relationship between seismicity and the rate change of ‘dynamic topography’ (that is, vertical normal stress from mantle flow). The associated predictive skill is greater than that of any of the other forcings we examined. We suggest that active mantle flow is a major contributor to seismogenic intraplate deformation, while gravitational potential energy variations have a minor role. Seismicity localization should occur where convective changes in vertical normal stress are modulated by lithospheric strength heterogeneities. Our results on deformation processes appear consistent with findings from other mobile belts4, and imply that mantle flow plays a significant and quantifiable part in shaping topography, tectonics, and seismic hazard within intraplate settings.

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Acknowledgements

We thank C. Kreemer for publishing his geodetic strain-rate models in electronic form, and C. Conrad for comments. All figures were created with Generic Mapping Tools28. Some analysis was based on data services provided by the Plate Boundary Observatory operated by UNAVCO for EarthScope and supported by the National Science Foundation (NSF; EAR-0350028 and EAR-0732947). T.W.B. was partially supported by NSF/US Geological Survey Southern California Earthquake Center, as well as EAR-1215720 and EAR-1215757. A.R.L. was supported by EAR-0955909 and EAR-1358622.

Author information

Affiliations

  1. Department of Earth Sciences, University of Southern California, Los Angeles, California 90089–0740, USA

    • Thorsten W. Becker
  2. Department of Geology, Utah State University, Logan, Utah 84322–4505, USA

    • Anthony R. Lowry
  3. Department of Sciences, Università Roma Tre, 00146 Roma, Italy

    • Claudio Faccenna
  4. Department of Earth and Planetary Sciences, The University of New Mexico, Albuquerque, New Mexico 87131, USA

    • Brandon Schmandt
  5. Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093–0225, USA

    • Adrian Borsa
  6. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    • Chunquan Yu

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Contributions

T.W.B. conducted the analysis and geodynamic modelling and wrote the paper with A.R.L. T.W.B., A.R.L. and C.F. designed the analysis and contributed to the writing. B.S. and C.Y. advised on geophysical constraints, A.B. provided assistance with GPS data, and all authors collaborated on interpretation of results.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Thorsten W. Becker.

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https://doi.org/10.1038/nature14867

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