Moving towards an improved index for assessing liquefaction hazard: Lessons from historical data

While Liquefaction Potential Index (LPI) has been used to assess liquefaction hazards worldwide, evaluations of LPI during recent earthquakes have found its performance to be inconsistent. In 1985, Ishihara considered the influence of the non-liquefied surface layer on the manifestation of liquefaction, and proposed an empirical approach to predict liquefaction surface effects. The study presented herein investigates the insights the boundary curves proposed by Ishihara may provide for improving the existing LPI framework. The result of the investigation is a novel Ishihara-inspired index, LPIISH. Its performance is evaluated using select liquefaction case histories and is compared to that of the existing LPI framework. For the selected case studies, LPIISH was found to be consonant with observed surface effects and showed improvement over LPI in mitigating false-positive predictions. Ultimately, the influence of non-liquefiable layers on surficial manifestation is complex, and further research is needed to fully elucidate and quantify these effects.