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Figure 3.4: Magnitude Scaling Factors Derived by Various Investigators (Youd and Idriss 1997)
Seed and Harder (1990) suggest correcting the CRR value for two additional factors, K σ
and K α , which are used to account for the influence of soil depth and the presence of
static shear stress (sloping ground condition), respectively. The factor K σ is used to
correct CRR for the effects of large overburden pressures that are typically found beneath
embankments, dams and deep fills. As the overburden pressure increases, the CSR
required to cause liquefaction (CSR L ) effectively decreases. For liquefiable materials at
shallow depths (less than 12 m) where most lateral spreads occur, the K σ correction factor
is generally near 1.0 (Figure 3.5). Recent recommendations pertaining to the correction
factors have been summarized by Youd and Idriss (1997).
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