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(A)(A)(B)(B)▲▲Figure 10. Comparison of CSR M7.5 for the Darfield andChristchurch earthquakes with CRR M7.5 for a site in Bexley(FC = 9%): A) profiles for DCP test; and B) profiles for SASWtest.In general, the selected critical layer thickness was thinnest forcases of lateral spreading with no ejecta, intermediate for lateralspreading with ejecta, and thickest for large sand boils withno associated lateral spreading. For example, the profile shownin Figure 10A laterally spread (see Figure 4) and there was asignificant amount of ejecta that vented to the ground surfacenearby. Using this information, and trends in the N DCPT ,shown in Figure 5B, the selected critical layer was ~2 m thick,as indicated in Figure 10A. Once the critical layers were determinedfor each test site, the N 1,60cs-SPTequiv values, CSR M7.5 ,and CRR M7.5 were averaged over these depths. The results wereplotted along with Youd et al. (2001) SPT CRR M7.5 curve inFigure 11A.A similar procedure as that outlined above was used tocompute the CSR M7.5 for the SASW test sites. However, theMSF proposed by Andrus and Stokoe (2000) was used instead▲ ▲ Figure 11. Comparison of predicted versus observed liquefaction:A) DCP test; and B) SASW test.of the average of the recommended range proposed by Youdet al. (2001). The reason for using slightly different MSFs wasto be consistent with how the respective cyclic resistance ratiocurves were developed from the observational data. Usingthe computed V S1 , the CRR M7.5 for the test site profiles werecalculated following the Andrus and Stokoe (2000) procedure;this procedure is also outlined in Youd et al. (2001).Comparisons of the computed CSR M7.5 for both the Darfieldand Christchurch earthquakes and CRR M7.5 for a test site inthe eastern Christchurch suburb of Bexley are shown in Figure10B. Consistent with the DCP test results, liquefaction ispredicted to occur at this site during both the Darfield andChristchurch earthquakes, with the liquefaction predicted tobe more severe during the Christchurch earthquake. Again,these predictions are in line with the post-earthquake observations.936 Seismological Research Letters Volume 82, Number 6 November/December 2011