Sensitivity of predicted liquefaction-induced lateral displacements from the 2010 Darfield and 2011 Christchurch earthquakes

Abstract

Liquefaction-induced lateral spreading in Christchurch and surrounding suburbs during the recent
\nCanterbury Earthquake Sequence (2010-2011) caused significant damage to structures and lifelines
\nlocated in close proximity to streams and rivers. Simplified methods used in current engineering
\npractice for predicting lateral ground displacements exhibit a high degree of epistemic uncertainty, but
\nprovide ‘order of magnitude’ estimates to appraise the hazard. We wish to compare model predictions to
\nfield measurements in order to assess the model’s capabilities and limitations with respect to
\nChristchurch conditions.
\nThe analysis presented focuses on the widely-used empirical model of Youd et al. (2002), developed
\nbased on multi-linear regression (MLR) of case history data from lateral spreading occurrence in Japan
\nand the US. Two issues arising from the application of this model to Christchurch were considered:
\n• Small data set of Standard Penetration Test (SPT) and soil gradation indices (fines content FC,
\nand mean grain size, D50) required for input. We attempt to use widely available CPT data with
\nsite specific correlations to FC and D50.
\n• Uncertainty associated with the model input parameters and their influence on predicted
\ndisplacements. This has been investigated for a specific location through a sensitivity analysis.