Developing Region-Specific Liquefaction Assessment Criterion for Bachu Region, China

Abstract

During the 2003 Bachu earthquake in China, the liquefaction phenomenon was widely observed. However, the standard penetration test–based method suggested in the national seismic design code in China significantly underestimates the liquefaction potential in Bachu. In this paper, a model bias factor is used to represent the effect of model uncertainty. The variability of the model bias factor associated with the national seismic design code method is investigated using 160 case histories collected from 7 regions in China. It is found that the statistics of the model bias factor vary from one region to another, indicating that the national seismic design code method is associated with different levels of accuracy when applied in different regions. Using the knowledge about the model bias factor learned from the seven regions as prior information, the distribution of the model bias factor is then updated with the region-specific data from Bachu based on Bayes’ theorem. The updated model bias factor is verified through liquefaction potential, and the expected number of liquefaction cases is consistent with the observed number of liquefaction cases. Base on the calibrated model bias factor in Bachu, a new liquefaction assessment criterion is then suggested for Bachu to achieve the target reliability level.