Magnitude scaling factors for soil liquefaction evaluations

Energy concepts are applied to the conditions that are likely to have existed at distant liquefaction sites in past earthquakes. From this, magnitude scaling factors are derived that reflect field cyclic strength conditions. It is shown in the paper that the factors are independent of the field acceleration assumed to have existed at the sites, and are only dependent on the magnitude-equivalent number of cycles relationship. These factors are compared with others based on laboratory cyclic strengths from Seed and Idriss and on statistical regression of data from field case histories of liquefaction. The factors derived based on energy concepts are similar to those derived by Ambraseys based on a statistical analyses of extensive liquefaction data. It is concluded that the factors derived in the paper based on energy concepts, or by Ambraseys, appropriately represent field conditions and avoid the limitations and extrapolations of the laboratory-based derivation by Seed and Idriss, and they are recommended for use in the analysis of liquefaction potential.