Improving Earthquake Locations

Locating earthquakes using P and S arrival times is a classic problem in seismology. However, improvements are still possible using methods such as waveform cross-correlation and relative relocation techniques that exploit the correlated travel-time results among nearby events caused by unmodeled 3D velocity structure. Over the years we have applied a variety of approaches to improve event location accuracy in southern California, Hawaii, Nevada, and other regions. These improved locations can be used to better delineate fault structures at depth, as shown in this example:

Earthquake locations for over 17,000 earthquakes in the Imperial Valley, California (1981–2005), as computed using: (left) single event location, (middle) source-specific station term (SSST) locations (Richards-Dinger and Shearer, 2000), and (right) waveform cross-correlation locations using results from Lin et al. (2007).

Our relocated catalogs for southern California are available from the SCEC Data Center.

Relevant papers with contributions from my group include:

  1. Matoza, R. S., P. G. Okubo, and P. M. Shearer, Comprehensive high-precision relocation of seismicity on the Island of Hawai'i 1986-2018, Earth Space Sci., 8, doi: 10.1029/2020EA001253, 2020.
  2. Ross, Z. E., D. T. Trugman, E. Hauksson, and P. M. Shearer, Searching for hidden earthquakes in Southern California, Science, 364, 767-771, doi: 10.1126/science.aaw6888, 2019.
  3. Koper, K. D., K. L. Pankow, J. C. Pechmann, J. M. Hale, R. Burlacu, W. L. Yeck, H. M. Benz, R. B. Herrmann, D. T. Trugman, and P. M. Shearer, Afterslip enhanced aftershock activity during the 2017 earthquake sequence near Sulphur Peak, Idaho, Geophys. Res. Lett., 45, doi: 10.1029/2017GL078196, 2018.
  4. Trugman, D. T., and P. M. Shearer, GrowClust: A hierarchical clustering algorithm for relative earthquake relocation, with application to the Spanish Springs and Sheldon, Nevada, earthquake sequences, Seismol. Res. Lett., 88, 1-13, doi: 10.1785/0220160188, 2017. (PDF)
  5. Buehler, J. S., and P. M. Shearer, Characterizing earthquake location uncertainty in North America using source-receiver reciprocity and USArray, Bull. Seismol. Soc. Am., 106, 2395-2401, doi: 10.1785/0120150173, 2016. (PDF)
  6. Matoza, R. S., P. M. Shearer, and P. G. Okubo, High-precision relocation of long-period events beneath the summit region of Kilauea Volcano, Hawaii, from 1986 to 2009, Geophys. Res. Lett., 41, doi:10.1002/2014GL059819, 2014. (PDF)
  7. Matoza, R. S., P. M. Shearer, G. Lin, C. J. Wolfe, and P. G. Okubo, Systematic relocation of seismicity on Hawaii Island from 1992 to 2009 using waveform cross correlation and cluster analysis, J. Geophys. Res., 118, doi: 10.1002/jgrb.50189, 2013.
  8. Hauksson, E., J Stock, R. Bilham, M. Boese, X. Chen, E. H. Fielding, J. Galetzka, K. W. Hudnut, K. Hutton, L. C. Jones, H. Kanamori, P. M. Shearer, J. Steidl, J. Treiman, S. Wei, and Wenzheng Yang, Report on the August 2012 Brawley earthquake swarm in Imperial Valley, Southern California, Seismol. Res. Lett., 84, 177-189, doi: 10.1785/0220120169, 2013. (PDF)
  9. Hauksson, E., W. Yang and P. M. Shearer, Waveform relocated earthquake catalog for southern California (1981 to June 2011), Bull. Seismol. Soc. Am., 102, 2239-2244, doi: 10.1785/0120120010, 2012.
  10. Chen, X., P. M. Shearer, and R. E. Abercrombie, Spatial migration of earthquakes within seismic clusters in Southern California: Evidence for fluid diffusion, J. Geophys. Res., 117, B04301, doi:10.1029/2011JB008973, 2012. (PDF)
  11. Castro, R. R., C. Valdes-Gonzalez, P. Shearer, V. Wong, L. Astiz, F. Vernon, A. Perez-Vertti, and A. Mendoza, The 3 August 2009 Mw Canal de Ballenas Region, Gulf of California, earthquake and its aftershocks, Bull. Seismol. Soc. Am., 101, 929-939, doi: 10.1785/0120100154, 2011.
  12. Castro, R., R., P. M. Shearer, L. Astiz, M. Suter, C. Jacques-Ayala and F. Vernon, The long lasting aftershock series of the 3 May 1887 Mw 7.5 Sonora earthquake in the Mexican Basin and Range Province, Bull. Seismol. Soc. Am., 100, 1153-1164, 2010.
  13. Lin, G., C. H. Thurber, H. Zhang, E. Hauksson, P. M. Shearer, F. Waldhauser, T. M. Brocher and J. Hardebeck, A California statewide three-dimensional seismic velocity model from both absolute and differential times, Bull. Seismol. Soc. Am., 100, 225-240, doi: 10.1785/0120090028, 2010.
  14. Lin, G., P.M. Shearer, and E. Hauksson, Applying a three-dimensional velocity model, waveform cross correlation, and cluster analysis to locate southern California seismicity from 1981 to 2005, J. Geophys. Res., 112, B12309, doi: 10.1029/2007JB004986, 2007.
  15. Lin, G., P.M. Shearer, and E. Hauksson, Applying a three-dimensional velocity model, waveform cross correlation, and cluster analysis to locate southern California seismicity from 1981 to 2005, J. Geophys. Res., 112, B12309, doi: 10.1029/2007JB004986, 2007.
  16. Lin, G., P.M. Shearer, E. Hauksson, and C.H. Thurber, A three-dimensional crustal seismic velocity model for southern California from a composite event method, J. Geophys. Res., 112, B11306, doi: 10.1029/2007JB004977, 2007.
  17. Lin, G., and P. Shearer, Estimating local Vp/Vs ratios within similar event clusters, Bull. Seismol. Soc. Am., 97, 379-388, doi: 10.1785/0120060115, 2007.
  18. Guzofski, C.A., J.H. Shaw, G. Lin, and P.M. Shearer, Seismically active wedge structure beneath the Coalinga anticline, San Joaquin basin, California, J. Geophys. Res., 112, B3, B03S05, doi: 10.1029/2006JB004465, 2007.
  19. Cochran, E.S., and P.M. Shearer, Infrasound events detected with the Southern California Seismic Network, Geophys. Res. Lett., 33, L19803, doi:10.1029/2006GL026951, 2006.
  20. Lin, G., and P. Shearer, The COMPLOC earthquake location package, Seismol. Res. Lett., 77, 440-444, 2006.
  21. Lin, G., P. Shearer and Y. Fialko, Obtaining absolute locations for quarry seismicity using remote sensing data, Bull. Seismol. Soc. Am., 96, 722-728, doi: 10.1785/0120050146, 2006.
  22. Shearer, P., E. Hauksson and G. Lin, Southern California hypocenter relocation with waveform cross-correlation, Part 2: Results using source-specific station terms and cluster analysis, Bull. Seismol. Soc. Am., 95, 904-915, doi:10.1785/0120040168, 2005.
  23. Hauksson, E. and P. Shearer, Southern California hypocenter relocation with waveform cross-correlation, Part 1: Results using the double-difference method, Bull. Seismol. Soc. Am., 95, 896-903, doi:10.1785/0120040167, 2005.
  24. Lin., G. and P. Shearer, Tests of relative earthquake location techniques using synthetic data, J. Geophys. Res., 110, B4, B04304, doi:10.1029/2004JB003380, 2005. (PDF)
  25. Konter J.G., H. Staudigel, S.R. Hart and P.M. Shearer, Seafloor seismic monitoring of an active submarine volcano: Local seismicity at Vailulu'u Seamount, Samoa, Geochem. Geophys. Geosyst., 5, Q06007, doi:10.1029/2004GC000702, 2004. (PDF)
  26. Grant, L.B. and P.M. Shearer, Activity of the offshore Newport-Inglewood Rose Canyon fault zone, coastal southern California, from relocated microseismicity, Bull. Seismol. Soc. Am., 94, 747-752, 2004. (PDF)
  27. Wolfe, C.J., P.G. Okubo, G. Ekstrom, M. Nettles and P.M. Shearer, Characteristics of deep (>= 13 km) Hawaiian earthquakes and Hawaiian earthquakes west of 155.55W, Geochem. Geophys. Geosyst., 5, Q04006, doi:10.1029/2003GC000618, 2004. (PDF)
  28. Wolfe, C.J., P.G. Okubo and P.M. Shearer, Mantle fault zone beneath Kilauea volcano, Hawaii, Science, 300, 478-480, 2003. (PDF)
  29. Shearer, P.M., J.L. Hardebeck, L. Astiz, and K.B. Richards-Dinger, Analysis of similar event clusters in aftershocks of the 1994 Northridge, California, earthquake, J. Geophys. Res., 108(B1), 2035, doi:10.1029/2001JB000685, 2003. (PDF)
  30. Shearer, P.M., Parallel fault strands at 9-km depth resolved on the Imperial Fault, Southern California, Geophys. Res. Lett., 29(14), doi: 10.1029/2002GL015302, 2002. (PDF)
  31. Shearer, P.M., Improving global seismic event locations using source-receiver reciprocity, Bull. Seismol. Soc. Am., 91, 594-603, 2001. (PDF)
  32. Richards-Dinger, K.B. and P.M. Shearer, Earthquake locations in southern California obtained using source specific station terms, J. Geophys. Res., 105, 10,939-10,960, 2000. (PDF)
  33. Astiz, L., and P.M. Shearer, Earthquake relocations in the inner Continental Borderland, offshore southern California, Bull. Seismol. Soc. Am., 90, 425-449, 2000. (PDF)
  34. Astiz, L., P.M. Shearer and D.C. Agnew, Precise relocations and stress-change calculations for the Upland earthquake sequence in southern California, J. Geophys. Res., 105, 2937-2853, 2000. (PDF)
  35. Shaw, J.H. and P.M. Shearer, An elusive blind-thrust fault beneath metropolitan Los Angeles, Science, 283, 1516-1518, 1999. (PDF)
  36. Shearer, P.M., Evidence for a fault at 18 km depth beneath Oak Ridge, southern California, from a cluster of small earthquakes, Bull. Seismol. So. Am., 88, 1327-1336, 1998.
  37. Shearer, P.M. and L. Astiz, Locating nuclear explosions using waveform cross-correlation, 19th Annual Seismic Research Symposium on Monitoring a Comprehensive Test Ban Treaty, Proceedings, 301-309, 1997. (PDF)
  38. Shearer, P.M., Improving local earthquake locations using the L1-norm and waveform cross-correlation: Application to the Whittier Narrows, California, aftershock sequence, J. Geophys. Res., 102, 8269-8283, 1997. (PDF)