Insights into Lateral Spread Displacement Patterns Using Remote Sensing Data from the 2011 Christchurch Earthquake

Abstract

High-resolution displacement observations of lateral spreading from optical image correlation are available for the 2011 Christchurch (Mw=6.2), New Zealand, earthquake, and these data were used to provide insights into the detailed displacement patterns during the earthquake and to quantitatively evaluate the performance of existing empirical models for lateral spread displacements. The observed displacements revealed important characteristics influencing the displacement patterns, including topographic terraces enhancing displacements in large regions between the terrace and the river, the combined effects of a free face and sloping ground on displacements near the river, and the effect of multiple free faces. These site characteristics can enhance displacements and should be considered when evaluating lateral spread movements. For the displacement models, on average, the Youd model underpredicts the observed displacements by more than a factor of 2, likely due to the strong magnitude scaling incorporated in the model. On average, the Zhang model is unbiased relative to the observed displacements but systematically overpredicts displacements for slopes greater than 1%. These results indicate the limitations of the existing lateral spread models and point toward the need for improvements in our understanding of lateral spread displacements.