Scattering

Earth's small-scale heterogeneity causes scattering of seismic waves, which produces the decaying wavetrain, or coda, observed following direct P and S arrivals at high frequencies. Statistical analysis and modeling of this scattered energy as a function of time and source-receiver geometry provides valuable constraints on Earth structure at length scales inaccessible to deterministic methods. For example, PKP precursor observations show that small-scale compositional heterogeneity must exist in the lowermost mantle (Hedlin et al., 1997) and PKKP precursor observations suggest random small-scale (~7 km) topography on the core-mantle boundary with RMS amplitude of ~400 m (Mancinelli and Shearer, 2016).

Relevant papers with contributions from my group include:

  1. Wang, W., and P. M. Shearer, An improved method to determine coda-Q, earthquake magnitude and site amplification: Theory and application to southern California, J. Geophys. Res., 124, 578-598, doi: 10.1029/2018JB015961, 2019.
  2. Buehler, J. S., N. J. Mancinelli, and P. M. Shearer, S-to-Rayleigh wave scattering from the continental margin observed at USArray, Geophys. Res. Lett., 45, 4719-4724, doi: 10.1029/2017GL076812, 2018.
  3. Wang, W., and P. M. Shearer, Using direct and coda wave envelopes to resolve the scattering and intrinsic attenuation structure of Southern California, J. Geophys. Res., 122, 7236-7251, doi: 10.1002/2016JB013810, 2017. (PDF)
  4. Mancinelli, N., and P. Shearer, Scattered energy from a rough core-mantle boundary modeled by a Monte Carlo seismic particle method: Application to PKKP precursors, Geophys. Res. Lett., 43, 7963-7972, doi: 10.1002/2016GL070286, 2016. (PDF)
  5. Mancinelli, N., P. Shearer, and Q. Liu, Constraints on the heterogeneity spectrum of Earth's upper mantle, J. Geophys. Res., 121, 1-19, doi: 10.1002/2015JB012641, 2016. (PDF)
  6. Mancinelli, N., P. Shearer, and C. Thomas, On the frequency dependence and spatial coherence of PKP precursor amplitudes, J. Geophys. Res., 121, 1873-1889, doi: 10.1002/2015JB012768, 2016. (PDF)
  7. Shearer, P.M., Seismic scattering in the deep Earth, in Treatise on Geophysics, Second Edition, Volume 1: Deep Earth Seismology, Schubert, G. (ed.), Elsevier Ltd., Oxford, p. 759-787, http://dx.doi.org/10.1016/B978-0-444-53802-4.00018-X, 2015. (PDF)
  8. Rost, S., P. S. Earle, P. M. Shearer, D. A. Frost, and N. D. Selby, Seismic detections of small-scale heterogeneities in the deep Earth, in The Earth's Heterogeneous Mantle, Springer Geophysics, doi: 10.1007/978-3-319-15627-9_12, p. 367-390, 2015. (PDF)
  9. Mancinelli, N. J., and P. M. Shearer, Reconciling discrepancies among estimates of small-scale mantle heterogeneity from PKP precursors, Geophys. J. Int., 195, 1721-1729, doi: 10.1093/gji/ggt319, 2013. (PDF)
  10. Earle, P. S., S. Rost, P. M. Shearer, and C. Thomas, Scattered P'P' waves observed at short distances, Bull. Seismol. Soc. Am., 101, 2843-2854, doi: 10.1785/0120110157, 2011. (PDF)
  11. Peng, Z., K. D. Koper, J. E. Vidale, F. Leyton, and P. Shearer, Inner-core fine-scale structure from scattered waves recorded by LASA, J. Geophys. Res., 113, doi: 10.1029/2007JB005412, 2008. (PDF)
  12. Shearer, P. M., and P.S. Earle, Observing and modeling elastic scattering in the deep Earth, in Advances in Geophysics, Volume 50: Earth Heterogeneity and Scattering Effects on Seismic Waves, H. Sato and M.C. Fehler (ed.), Elsevier Ltd., Oxford, p. 167-193, 2008. (PDF)
  13. Shearer, P.M., Seismic scattering in the deep Earth, in Treatise on Geophysics, Volume 1: Deep Earth Structure, Schubert, G. (ed.), Elsevier Ltd., Oxford, p. 695-730, 2007. (PDF)
  14. Shearer, P.M. and P.S Earle, The global short-period wavefield modelled with a Monte Carlo seismic phonon method, Geophys. J. Int., 158, 1103-1117, 2004. (PDF)
  15. Hedlin, M.A.H., and P.M. Shearer, Probing mid-mantle heterogeneity using PKP coda waves, Phys. Earth Planet. Int., 130, 195-208, 2002. (PDF)
  16. Earle, P.S. and P.M. Shearer, Distribution of fine-scale mantle heterogeneity from observations of Pdiff coda, Bull. Seismol. Soc. Am., 91, 1875-1881, 2001. (PDF)
  17. Hedlin, M.A.H. and P.M. Shearer, An analysis of large scale variations in small-scale mantle heterogeneity using Global Seismic Network recordings of precursors to PKP, J. Geophys. Res., 105, 13,655-13,673, 2000. (PDF)
  18. Earle, P.S. and P.M. Shearer, Observations of high-frequency scattered energy associated with the core phase PKKP, Geophys. Res. Lett., 25, 405-408, 1998. (PDF)
  19. Shearer, P.M., M.A.H. Hedlin and P.S. Earle, PKP and PKKP precursor observations: Implications for the small-scale structure of the deep mantle and core, The Core-Mantle Boundary Region, AGU Geodynamics Series, 28, 37-55, 1998.
  20. Hedlin, M.A.H., P.M. Shearer and P.S. Earle, Seismic evidence for small-scale heterogeneity throughout the Earth's mantle, Nature, 387, 145-150, 1997. (PDF)