Annual probability and return period of soil liquefaction in Yuanlin, Taiwan attributed to Chelungpu Fault and Changhua Fault

In this paper the results of a case study of the annual probability and return period of soil liquefaction in Yuanlin, Taiwan, the town that suffered significant liquefaction damage in the 1999 Chi-Chi earthquake, are presented. As part of this case study, a framework for determining the average annual probability of liquefaction (AAPL) that is attributed to a known fault is developed. This framework is formulated by considering the uncertainties in both liquefaction resistance and liquefaction loading. For liquefaction loading, the seismic hazard from a known fault is considered; and for liquefaction resistance, soil parameters, characterized mainly by cone penetration test (CPT) and standard penetration test (SPT), and their uncertainties are considered. Additionally, model uncertainty of the empirically-developed liquefaction resistance models, based either on CPT or SPT, is considered in the analysis for the annual liquefaction probabilities. The results of the case study show that the proposed framework is applicable for site-specific analysis of liquefaction potential or for mapping liquefaction potential in a given town (or city). Furthermore, the AAPL and return period determined based on SPTs are found to be comparable with those determined with CPTs. The results of the case study provide some guidance for future engineering planning and regulation consideration in the Yuanlin, Taiwan area.