Return Period of Soil Liquefaction

The paper describes a performance-based approach to the evaluation of liquefaction potential, and shows how it can be used to account for the entire range of potential ground shaking. The result is a direct estimate of the return period of liquefaction, rather than a factor of safety or probability of liquefaction conditional upon ground shaking with some specified return period. As such, the performance-based approach can be considered to produce a more complete and consistent indication of the actual likelihood of liquefaction at a given location than conventional procedures. In this paper, the performance-based procedure is introduced and used to compare likelihoods of the initiation of liquefaction at identical sites located in areas of different seismicity. The results indicate that the likelihood of liquefaction depends on the position and slope of the peak acceleration hazard curve, and on the distribution of earthquake magnitudes contributing to the ground motion hazard. The results also show that the consistent use of conventional procedures for the evaluation of liquefaction potential produces inconsistent actual likelihoods of liquefaction.