Source Spectra and Attenuation

Analyses of P- and S-wave spectra provides information regarding earthquake source properties, including radiated energy and Brune stress drop, that are related to earthquake dynamics. However, observed spectra are also strongly sensitive to attenuation along source-receiver ray paths, so separating source and attenuation effects is a continuing challenge in observational seismology. Earthquakes of similar moment often vary greatly in their radiated energy at high-frequencies and understanding the origins of these differences is important in earthquake physics and strong motion seismology, as shown in this figure:

A comparison of spatial variations in: (a) estimated earthquake stress drops, and (b) peak-ground-acceleration (PGA) residuals, for the San Francisco Bay region. Note the strong correlation between higher-than-average stress drops and higher-than-average PGA values, both plotted in red. From Trugman and Shearer (2018).

Relevant papers with contributions from my group include:

  1. Shearer, P. M., and R. E. Abercrombie, Calibrating spectral decomposition of local earthquake using borehole seismic records—Results for the 1992 Big Bear aftershocks in southern California, J. Geophys. Res., 126, doi: 10.1029/2020JB020561, 2021.
  2. Shearer, P. M., R. E. Abercrombie, D. T. Trugman, and W. Wang, Comparing EGF methods for estimating corner frequency and stress drop from P-wave spectra, J. Geophys. Res., 124, 3966-3986, doi: 10.1029/2018JB016957, 2019.
  3. 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.
  4. Trugman, D. T., and P. M. Shearer, Strong correlation between stress drop and peak ground acceleration for recent M 1-4 earthquakes in the San Francisco Bay area, Bull. Seismol. Soc. Am., 929-945, doi: 10.1785/0120170245, 2018.
  5. Trugman, D. T., S. L. Dougherty, E. S. Cochran, and P. M. Shearer, Source spectral properties of small to moderate earthquakes in southern Kansas, J. Geophys. Res., 122, 8021-8034, doi: 10.1002/2017JB014649, 2017. (PDF)
  6. 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)
  7. Trugman, D. T., and P. M. Shearer, Application of an improved spectral decomposition method to examine earthquake source scaling in southern California, J. Geophys. Res., 122, 2890-2910, doi: 10.1002/2017JB013971, 2017. (PDF)
  8. Denolle, M. A., and P. M. Shearer, New perspectives on self-similarity for shallow thrust earthquakes, J. Geophys. Res., 121, 6533-6565, doi: 10.1002/2016JB013105, 2016. (PDF)
  9. Matoza, R. S., B. A. Chout, P. B. Dawson, P. M. Shearer, M. M. Haney, G. P. Waite, S. P. Moran, T. D. Mikesell, Source mechanism of small long-period events at Mount St. Helens in July 2005 using template matching, phase-weighted stacking, and full-waveform inversion, J. Geophys. Res., 120, 6351-6364, doi: 10.1002/2015JB012279, 2015. (PDF)
  10. Chen, X., and P. M. Shearer, Analysis of foreshock sequences in California and implications for earthquake triggering, Pure Appl. Geophys., doi: 10.1007/s00024-015-1103-0, 2015. (PDF)
  11. Goebel, T. H. W., E. Hauksson, P. M. Shearer, and J. P. Ampuero, Stress drop heterogeneity within tectonically complex regions: A case study of San Gorgonio Pass, southern California, Geophys. J. Int., 202, 514-528, 2015. (PDF)
  12. Kaneko, Y., and P. M. Shearer, Variability of seismic source spectra, estimated stress drop and radiated energy, derived from cohesive-zone models of symmetrical and asymmetrical circular and elliptical ruptures, J. Geophys. Res., 120, doi: 10.1002/2014JB011642, 2015. (PDF)
  13. Uchide, T., P. M. Shearer, and K Imanishi, Stress drop variations among small earthquakes before the 2011 Tohoku-oki, Japan, earthquake and implications for the main shock, J. Geophys. Res., 119, 7164-7174, doi: 10.1002/2014JB010943, 2014. (PDF)
  14. Kaneko, Y., and P. M. Shearer, Seismic source spectra and estimated stress drop from cohesive-zone models of circular subshear rupture, Geophys. J. Int., 197, 1002-1015, doi: 10.1093/gji/ggu030, 2014. (PDF)
  15. Chen, X., and P. M. Shearer, California foreshock sequences suggest aseismic triggering process, Geophys. Res. Lett., 40, doi:10.1002/grl.50444, 2013. (PDF)
  16. Kane, D. L., P. M. Shearer, B. P. Goertz-Allmann, and F. L. Vernon, Rupture directivity of small earthquakes at Parkfield, J. Geophys. Res., 118, doi: 10.1029/2012JB009675, 2013. (PDF)
  17. Kane, D. L., G. A. Prieto, F. L. Vernon, and P. M. Shearer, Quantifying seismic source parameter uncertainties, Bull. Seismol. Soc. Am., 101, 535-543, doi: 10.1785/0120100166, 2011. (PDF)
  18. Chen, X., and P. M. Shearer, Comprehensive analysis of earthquake source spectra and swarms in the Salton Trough, California, J. Geophys. Res., 116, doi:10.1029/2011JB008263, 2011. (please note correction at J. Geophys. Res., 118, doi: 10.1002/jgrb.50098, 2013) (PDF)
  19. Allmann, B. B., and P. M. Shearer, Global variations of stress drop for moderate to large earthquakes, J. Geophys. Res., 114, doi: 10.1029/2009JB005821, 2009. (PDF)
  20. Allmann, B. P., P. M. Shearer, and E. Hauksson, Spectral discrimination between quarry blasts and earthquakes in southern California, Bull. Seismol. Soc. Am., 98, 2073-2079, doi: 10.1785/0120070215, 2008. (PDF)
  21. Oki, S., and P. M. Shearer, Mantle Q structure from S-P differential attenuation measurements, J. Geophys. Res., 113, doi: 10.1029/2007JB005567, 2008. (PDF)
  22. Prieto, G.A., D.J. Thomson, F.L. Vernon, P.M. Shearer, and R.L. Parker, Confidence intervals for earthquake source parameters, Geophys. J. Int., 168, 1227-1234, doi: 10.1111/j.1365-246X.2006.03257.x, 2007.
  23. Allmann, B.P., and P.M. Shearer, Spatial and temporal stress drop variations in small earthquakes near Parkfield, California, J. Geophys. Res., 112, B4, B04305, doi: 10.1029/2006JB004395, 2007. (PDF)
  24. Lawrence, J. F., P. M. Shearer, and G. Masters, Mapping attenuation beneath North America using waveform cross-correlation and cluster analysis, Geophys. Res. Lett., 33, L07315, doi:10.1029/2006GL025813, 2006. (PDF)
  25. Hauksson, E., and P. M. Shearer, Attenuation models (Qp and Qs) in three dimensions of the southern California crust: Inferred fluid saturation at seismogenic depths, J. Geophys. Res., 111, B05302, doi:10.1029/2005JB003947, 2006. (PDF)
  26. Shearer, P. M., G. A. Prieto, and E. Hauksson, Comprehensive analysis of earthquake source spectra in southern California, J. Geophys. Res., 111, B06303, doi:10.1029/2005JB003979, 2006. (PDF)
  27. Prieto, G.A., R.L. Parker, F.L. Vernon, P.M. Shearer and D.J. Thomson, Uncertainties in earthquake source spectrum estimation using empirical Green functions, in Earthquakes: Radiated Energy and the Physics of Faulting, AGU Geophysical Monograph Series 170, doi:10.1029/170GM08, 2006.
  28. Warren, L.M. and P.M. Shearer, Using the effects of depth phases on P-wave spectra to determine earthquake depths, Bull. Seismol. Soc. Am., 95, 173-184, 2005. (PDF)
  29. Prieto, G., P.M. Shearer, F.L. Vernon and D. Kilb, Earthquake source scaling and self-similarity estimation from stacking P and S spectra, J. Geophys. Res., 109, B8, B08310, doi:10.1029/2004JB003084, 2004. (PDF)
  30. Warren, L.M., and P.M. Shearer, Mapping lateral variations in upper mantle attenuation structure by stacking P and PP spectra, J. Geophys. Res., 107(B12), 2342, doi: 10.1029/2001JB001195, 2002. (PDF)
  31. Warren, L.M. and P.M. Shearer, Investigating the frequency dependence of mantle Q by stacking P and PP spectra, J. Geophys. Res., 105, 25,391-25,402, 2000. (PDF)
  32. Bhattacharyya, J., G. Masters and P. Shearer, Global variations of shear wave attenuation in the upper mantle, J. Geophys Res., 101, 22,273-22,289, 1996. (PDF)
  33. Aster, R.C. and P.M. Shearer, High-frequency borehole seismograms recorded in the San Jacinto Fault Zone, Southern California, Part 2. Attenuation and site effects, Bull. Seismol. Soc. Am., 81, 1081-1100, 1991.