Stress triggering of the 1994 M = 6.7 Northridge, California, Earthquake by its predecessors

Science

Volumn 265, Issue 5177, 1994, Pages 1432-1435

  Stein, Ross S ^a   King, Geoffrey C P ^b   Lin, Jian ^c  

^a U S GEOLOGICAL SURVEY   (United States)

^b UMR 7063   (France)

^c WOODS HOLE OCEANOGRAPHIC INSTITUTION   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ELYSIA; QUERCUS;

AFTERSHOCK; AFTERSHOCKS; EARTHQUAKE TRIGGERING; NORTHRIDGE EARTHQUAKE 1994; STRESS HISTORY; STRESS TRANSFER;

USA, CALIFORNIA;

EID: 0028164186     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.265.5177.1432     Document Type: Article

References (42)

1. T. L. Davis, J. Namson, R. F. Yerkes, J. Geophys. Res. 94, 9644 (1989); R. S. Stein and R. S. Yeats, Sci. Am. 260, 48 (June 1989).
2. T. L. Davis, J. Namson, R. F. Yerkes, J. Geophys. Res. 94, 9644 (1989); R. S. Stein and R. S. Yeats, Sci. Am. 260, 48 (June 1989).
3. T. H. Heaton, Bull. Seismol. Soc. Am. 72, 2037 (1982). We simulated the variable slip model by four patches of slip on the San Fernando fault and five slip patches on the Sierra Madre fault.
4. J. H. Whitcomb, C. R. Allen, J. D. Garmany, J. A. Hileman, Rev. Geophys. 11, 693 (1973).
5. E. Hauksson, K. Hutton, H. Kanamori, L. Jones, J. Mori, Abstr. Annu. Meet. Seismol. Soc. Am. 89, 4 (1994).
6. A ∼3000-year repeat time for the Northridge earthquake fault is estimated by dividing the 3.5-m coseismic slip of K. W. Hudnut et al. (27) by the ∼1-mm/ year fault slip rate argued by R. S. Yeats (in preparation). R. Crook Jr., C. R. Allen, B. Kamb, C. M. Payne, and R. J. Payne [U.S. Geol. Surv. Prof. Pap. 1339, 27 (1987)] suggest a several-thousand-year repeat time for the western Sierra Madre fault, on which part of the San Fernando earthquake occurred, although M. Bonilla [San Fernando, California, Earthquake of 9 February 1971, L. M. Murphy, Ed. (National Oceanic and Atmospheric Administration, Washington, DC, 1973), vol. 3, p. 174] found a previous event 100 to 300 years old on a subsidiary strand of the San Fernando fault.
7. A ∼3000-year repeat time for the Northridge earthquake fault is estimated by dividing the 3.5-m coseismic slip of K. W. Hudnut et al. (27) by the ∼1-mm/ year fault slip rate argued by R. S. Yeats (in preparation). R. Crook Jr., C. R. Allen, B. Kamb, C. M. Payne, and R. J. Payne [U.S. Geol. Surv. Prof. Pap. 1339, 27 (1987)] suggest a several-thousand-year repeat time for the western Sierra Madre fault, on which part of the San Fernando earthquake occurred, although M. Bonilla [San Fernando, California, Earthquake of 9 February 1971, L. M. Murphy, Ed. (National Oceanic and Atmospheric Administration, Washington, DC, 1973), vol. 3, p. 174] found a previous event 100 to 300 years old on a subsidiary strand of the San Fernando fault.
8. 5 bars. Very close to the slipped fault, the Coulomb stress change depends on the unknown details of the fault slip. Thus, stress changes calculated within a few kilometers of the earthquake sources are not meaningful. In contrast, stress changes far from the fault do not depend on the detailed slip function and are thus most diagnostic.
9. R. S. Stein and M. Lisowski, J. Geophys. Res. 88, 6477 (1983); R. A. Harris and R. W. Simpson, Nature 360, 251 (1992); S. C. Jaumé and L. R. Sykes, Science 258, 1325 (1992).
10. R. S. Stein and M. Lisowski, J. Geophys. Res. 88, 6477 (1983); R. A. Harris and R. W. Simpson, Nature 360, 251 (1992); S. C. Jaumé and L. R. Sykes, Science 258, 1325 (1992).
11. R. S. Stein and M. Lisowski, J. Geophys. Res. 88, 6477 (1983); R. A. Harris and R. W. Simpson, Nature 360, 251 (1992); S. C. Jaumé and L. R. Sykes, Science 258, 1325 (1992).
12. P. A. Reasenberg and R. W. Simpson, Science 255, 1687 (1992).
13. R. S. Stein, G. C. P. King, J. Lin, ibid. 258, 1328 (1992).
14. r = 100 bars. Results are modestly sensitive to the assumed friction coefficient, which can range between 0 and 0.75, with lower μ corresponding to higher fluid pressure. Because we have little independent evidence to assign μ, we adopt a mid-range value of 0.4. A detailed sensitivity analysis is presented in (11).
15. G. C. P. King, R. S. Stein, J. Lin, Bull. Seismol. Soc. Am. 84, 935 (1994).
16. The Coulomb stress change on optimally oriented faults is sensitive to the orientation of the regional tectonic stress field. Inversion of small-earthquake focal mechanisms and 1971-1988 aftershock sequences in the greater Los Angeles region [J. W. Gephart and D. W. Forsyth, J. Geophys. Res. 89, 9305 (1984); L. M. Jones, ibid. 93, 8869 (1988); E. Hauksson, ibid. 95, 15365 (1990); _ and L. M. Jones, ibid. 96, 8143 (1991)] yields consistent values for the principal compressional axis of NO° to N12° E from the San Andreas fault south to Los Angeles, and N10° E to N32° E from south Los Angeles to Newport. Borehole breakouts of 10 oil wells in the Los Angeles and northeastern Ventura basin axis [V. S. Mount and J. Suppe, J. Geophys. Res. 97, 11995 (1992)] furnish a N21° E compression. Here we use N16° E, an average of these measurements.
17. The Coulomb stress change on optimally oriented faults is sensitive to the orientation of the regional tectonic stress field. Inversion of small-earthquake focal mechanisms and 1971-1988 aftershock sequences in the greater Los Angeles region [J. W. Gephart and D. W. Forsyth, J. Geophys. Res. 89, 9305 (1984); L. M. Jones, ibid. 93, 8869 (1988); E. Hauksson, ibid. 95, 15365 (1990); _ and L. M. Jones, ibid. 96, 8143 (1991)] yields consistent values for the principal compressional axis of NO° to N12° E from the San Andreas fault south to Los Angeles, and N10° E to N32° E from south Los Angeles to Newport. Borehole breakouts of 10 oil wells in the Los Angeles and northeastern Ventura basin axis [V. S. Mount and J. Suppe, J. Geophys. Res. 97, 11995 (1992)] furnish a N21° E compression. Here we use N16° E, an average of these measurements.
18. The Coulomb stress change on optimally oriented faults is sensitive to the orientation of the regional tectonic stress field. Inversion of small-earthquake focal mechanisms and 1971-1988 aftershock sequences in the greater Los Angeles region [J. W. Gephart and D. W. Forsyth, J. Geophys. Res. 89, 9305 (1984); L. M. Jones, ibid. 93, 8869 (1988); E. Hauksson, ibid. 95, 15365 (1990); _ and L. M. Jones, ibid. 96, 8143 (1991)] yields consistent values for the principal compressional axis of NO° to N12° E from the San Andreas fault south to Los Angeles, and N10° E to N32° E from south Los Angeles to Newport. Borehole breakouts of 10 oil wells in the Los Angeles and northeastern Ventura basin axis [V. S. Mount and J. Suppe, J. Geophys. Res. 97, 11995 (1992)] furnish a N21° E compression. Here we use N16° E, an average of these measurements.
19. The Coulomb stress change on optimally oriented faults is sensitive to the orientation of the regional tectonic stress field. Inversion of small-earthquake focal mechanisms and 1971-1988 aftershock sequences in the greater Los Angeles region [J. W. Gephart and D. W. Forsyth, J. Geophys. Res. 89, 9305 (1984); L. M. Jones, ibid. 93, 8869 (1988); E. Hauksson, ibid. 95, 15365 (1990); _ and L. M. Jones, ibid. 96, 8143 (1991)] yields consistent values for the principal compressional axis of NO° to N12° E from the San Andreas fault south to Los Angeles, and N10° E to N32° E from south Los Angeles to Newport. Borehole breakouts of 10 oil wells in the Los Angeles and northeastern Ventura basin axis [V. S. Mount and J. Suppe, J. Geophys. Res. 97, 11995 (1992)] furnish a N21° E compression. Here we use N16° E, an average of these measurements.
20. The Coulomb stress change on optimally oriented faults is sensitive to the orientation of the regional tectonic stress field. Inversion of small-earthquake focal mechanisms and 1971-1988 aftershock sequences in the greater Los Angeles region [J. W. Gephart and D. W. Forsyth, J. Geophys. Res. 89, 9305 (1984); L. M. Jones, ibid. 93, 8869 (1988); E. Hauksson, ibid. 95, 15365 (1990); _ and L. M. Jones, ibid. 96, 8143 (1991)] yields consistent values for the principal compressional axis of NO° to N12° E from the San Andreas fault south to Los Angeles, and N10° E to N32° E from south Los Angeles to Newport. Borehole breakouts of 10 oil wells in the Los Angeles and northeastern Ventura basin axis [V. S. Mount and J. Suppe, J. Geophys. Res. 97, 11995 (1992)] furnish a N21° E compression. Here we use N16° E, an average of these measurements.
21. 25 dyne-cm earthquake by a 23-km-long, 80° N-dipping oblique fault with tapered slip at a depth of 2 to 17 km extending between the main shock and the largest aftershock.
22. R. S. Stein and W. Thatcher, J. Geophys. Res. 86, 4913 (1981).
23. We use μ = 0.4 and a N16° E regional stress direction. Calculated stress increases at the future Whittier Narrows and Northridge sites are twice as high for μ = 0.75 than for μ = 0.0. A N6° E direction favors failure at the Northridge earthquake site more than at Whittier Narrows; a N26° E direction favors rupture at Whittier Narrows more than at Northridge.
24. No corresponding seismicity rate declines are seen after the 1971 earthquake, perhaps because rate decreases are harder to detect, as described in (8).
25. On the basis of preliminary seismic [D. J. Wald and T. H. Heaton, U.S. Geol. Surv. Open-File Rep. 94-278 (1994); (18)] and geodetic (27) evidence, coseismic fault slip stops 6 to 8 km below the ground surface.
26. D.S. Dreger et al., Abstr. Annu. Meet. Seismol. Soc. Am. 89, 11 (1994).
27. D. Ponti et al., ibid., p. 31.
28. M. Lisowski, J. C. Savage, and W. H. Prescott [J. Geophys. Res. 96, 8369 (1991)] measured a maximum shear strain rate in the Transverse Ranges northwest and northeast of Los Angeles to be about 0.13 μstrain/ year, which yields a shear stress rate of 0.08 bars/year, with a higher value closer to the San Andreas fault. The principal compression rate is also about 0.08 bar/year.
29. A typical earthquake shear stress drop is 10 to 100 bars.
30. D. P. Hill et al., Science 260, 1617 (1993).
31. R. E. Abercrombie [Proceedings of the VIIth International Symposium on the Observation of the Continental Crust Through Drilling, Santa Fe, NM, 25 to 30 April 1994, p. 221] found that the 10- to 100-bar static stress drops Δτ of M ≥ -1 earthquakes recorded in the Cajon Pass borehole are indistinguishable from those of larger shocks. Thus, there is no evidence that the ∼1-bar stress changes we report can cause microearthquakes unless the faults are already close to failure.
32. R. Abercrombie and J. Mori [Bull. Seismol. Soc. Am. 84, 725 (1994)] advance such a case for the Landers earthquake.
33. This could occur because the stress change occurs at a fault asperity or because the system as a whole is in a state of self-organized criticality [see, for example, P. A. Cowie, C. Vabbeste, D. Sornette, J. Geophys. Res. 98, 21809 (1993)].
34. It is also possible that the dynamic stresses play a role in earthquake triggering. Hill et al. (22) and J. G. Anderson et al. [Bull. Seismol. Soc. Am. 84, 863 (1994)] argue that distant aftershocks of the Landers earthquake were triggered by dynamic strains associated with the Landers rupture. P. Spudich, L. K. Steck, M. Hellweg, J. B. Reicher, and L. M. Baker (J. Geophys. Res., in press) suggest that at the site of the Big Bear event, the dynamic stresses are 3 to 6 times larger than the static stress changes, but they persist for <20 s and do not have lobes of stress decrease.
35. It is also possible that the dynamic stresses play a role in earthquake triggering. Hill et al. (22) and J. G. Anderson et al. [Bull. Seismol. Soc. Am. 84, 863 (1994)] argue that distant aftershocks of the Landers earthquake were triggered by dynamic strains associated with the Landers rupture. P. Spudich, L. K. Steck, M. Hellweg, J. B. Reicher, and L. M. Baker (J. Geophys. Res., in press) suggest that at the site of the Big Bear event, the dynamic stresses are 3 to 6 times larger than the static stress changes, but they persist for <20 s and do not have lobes of stress decrease.
36. K. W. Hudnut et al., Abstr. Annu. Meet. Seismol. Soc. Am. 89, 40 (1994).
37. J. Lin and R. S. Stein, J. Geophys. Res. 94, 9614 (1989).
38. E. Hauksson, L. M. Jones, K. Hutton, D. Eberhart-Phillips, ibid. 98, 19835 (1993).
39. D. J. Wald and T. H. Heaton, Bull. Seismol. Soc. Am. 84, 668 (1994).
40. L. E. Jones, S. E. Hough, D. V. Helmberger, Geophys. Res. Lett. 20, 1907 (1993).
41. 26 dyne-cm. This model, based on geodetic observations, likely illuminates the fault patch with greatest slip but underestimates the fault area. See (27).
42. We thank R. W. Simpson, for discussion and extensive calibration of our respective programs, and M. H. Murray, for sharing his preliminary geodetic models of the Northridge earthquake. We also thank W. Thatcher, J. Savage, T. Heaton, P. Reasenberg, and two anonymous referees for thoughtful reviews. We are grateful for the financial and scientific support of the Southern California Earthquake Center.