Back-Projection

Large earthquake ruptures radiate seismic energy over an extended fault plane. Long-period seismic radiation can be related to moment release and the slip distribution on the fault, but high-frequencies are more random in character and measure bursts of energy caused by fault and rupture complexity. Back-projection is a simple and surprisingly effective method for inverting high-frequency seismograms to image earthquake ruptures. It is related to migration in reflection seismology and reverse time methods in acoustic imaging.

Here is a back-projection animation from Ishii et al. (2005) of the 2004 Sumatra M 9.3 earthquake:
Propagation of rupture front as imaged by the Hi-Net array in Japan. The plotted quantity on the right is the squared amplitude of the back-projected stacks, i.e., proportional to released energy at high frequencies.

Relevant papers with contributions from my group include:

  1. Fan, W., and P. M. Shearer, Coherent seismic arrivals in the P wave coda of the 2012 Mw 7.2 Sumatra earthquake: Water reverberations or an early aftershock?, J. Geophys. Res., 123, 3147-3159, doi: 10.1002/2018JB015573, 2018.
  2. Fan, W., and P. M. Shearer, Investigation of backprojection uncertainties with M6 earthquakes, J. Geophys. Res., 122, 7966-7986, doi: 10.1002/2017JB014495, 2017. (PDF)
  3. Fan, W., D. Bassett, J. Jiang, P. M. Shearer, and C. Ji, Rupture evolution of the 2006 Java tsunami earthquake and the possible role of splay faults, Tectonophysics, 721, 143-150, 2017. (PDF)
  4. Fan, W., and P. M. Shearer, Local near instantaneously dynamically triggered aftershocks of large earthquakes, Science, 353, 1133-1136, doi: 10.1126/science.aag0013, 2016. REPRINT
  5. Fan, W., P. M. Shearer, C. Ji, and D. Bassett, Multiple branching rupture of the 2009 Tonga-Samoa earthquake, J. Geophys. Res., 121, doi: 10.1002/2016JB012945, 2016. (PDF)
  6. Fan, W., and P. M. Shearer, Fault interactions and triggering during the 10 January 2012 Mw 7.2 Sumatra earthquake, Geophys. Res. Lett., 43, 1934-1942, doi: 10.1002/2015GL067785, 2016. (PDF)
  7. Fan, W., and P. M. Shearer, Detailed rupture imaging of the 25 April 2015 Nepal earthquake using teleseismic P waves, Geophys. Res. Lett., 42, 7467-7475, doi: 10.1002/2015GL064587, 2015. (PDF)
  8. Uchide, T., H. Yao, and P. M. Shearer, Spatio-temporal distribution of fault slip and high-frequency radiation of the 2010 El Mayor-Cucapah, Mexico earthquake, J. Geophys. Res., 118, doi: 10.1002/jgrb.50144, 2013. (PDF)
  9. Yao, H., P. M. Shearer, and P. Gerstoft, Compressive sensing of frequency-dependent seismic radiation from subduction zone megathrust ruptures, Proc. Nat. Acad. Sci., 110, www.pnas.org/cgi/doi/10.1073/pnas.1212790110, 2013. (PDF)
  10. Yao, H., P. M. Shearer and P. Gerstoft, Subevent location and rupture imaging using iterative backprojection for the 2011 Tohoku Mw 9.0 earthquake, Geophys. J. Int., 190, 1152-1168, doi: 10.1111/j.1365-246X.2012.05541.x, 2012. (PDF)
  11. Kiser, E., M. Ishii, C. H. Langmuir, P. M. Shearer, and H. Hirose, Insights into the mechanism of intermediate-depth earthquakes from source properties as imaged by back-projection of multiple seismic phases, J. Geophys. Res., 116, doi: 10.1029/2010JB007831, 2011. (PDF)
  12. Yao, H., P. Gerstoft, P. M. Shearer, and C. Mecklenbrauker, Compressive sensing of the Tohuku-Oki Mw 9.0 earthquake: Frequency-dependent rupture modes, Geophys. Res. Lett., 38, doi:10.1029/2011GL049223, 2011. (PDF)
  13. Shearer, P. and R. Burgmann, Lessons learned from the 2004 Sumatra-Andaman megathrust rupture, Annu. Rev. Earth Planet. Sci., 38, 103-131, doi: 10.1146/annurev-earth-040809-152537, 2010. (PDF)
  14. Walker, K. T., and P. M. Shearer, Illuminating the near-sonic rupture velocities of the intracontinental Kokoxili Mw 7.8 and Denali fault Mw 7.9 strike-slip earthquakes with global P wave back projection imaging, J. Geophys. Res., 114, doi: 10.1029/2008JB005738, 2009. (PDF)
  15. Allmann, B.P., and P.M. Shearer, A high-frequency secondary event during the 2004 Parkfield earthquake, Science, 318, 1279, doi: 10.1126/science.1146537, 2007. (PDF)
  16. Ishii, M., P.M. Shearer, H. Houston, and J.E. Vidale, Teleseismic P wave imaging of the 26 December 2004 Sumatra-Andaman and 28 March 2005 Sumatra earthquake ruptures using the Hi-net array, J. Geophys. Res., 112, B11307, doi:10.1029/2006JB004700, 2007. (PDF)
  17. Ishii, M., P.M. Shearer, H. Houston and J.E. Vidale, Extent, duration and speed of the 2004 Sumatra-Andaman earthquake imaged by the Hi-Net array, Nature, doi: 10.1038/nature03675, 2005. (PDF)