Christchurch, New Zealand, experienced four major earthquakes (Mw 5.9 to 7.1) since 4 September 2010 that triggered localized to widespread liquefaction. Liquefaction caused significant damage to residential foundations due to ground subsidence, ground failure, and lateral spreading. This paper describes the land damage assessment process for Christchurch, including the collection and processing of extensive data and observations related to liquefaction, the characterization of liquefaction effects on land performance, and the quantification of losses for insurance compensation purposes. The paper also examines the effectiveness of several existing liquefaction vulnerability parameters and a new parameter developed through this research, Liquefaction Severity Number ( LSN), in explaining the observed liquefaction-induced damage in residential areas of Christchurch using results from 11,500 cone penetration tests (CPTs) as well as a robust regional groundwater model.

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The efficacy of various ground motion intensity measures (IM's) in the prediction of spatially distributed seismic demands (Engineering Demand Parameters, EDP's) within a structure is investigated. This has direct implications to building-specific seismic loss estimation, where the seismic demand on different components is dependent on the location of the component in the structure. Several common intensity measures are investigated in terms of their ability to predict the spatially distributed demands in a 10-storey office building, which is measured in terms of maximum interstorey drift ratios and maximum floor accelerations. It is found that the ability of an IM to efficiently predict a specific EDP depends on the similarity between the frequency range of the ground motion which controls the IM and that of the EDP. An IM's predictability has a direct effect on the median response demands for ground motions scaled to a specified probability of exceedance from a ground motion hazard curve. All of the IM's investigated were found to be insufficient with respect to at least one of magnitude, source-to-site distance, or epsilon when predicting all peak interstorey drifts and peak floor accelerations in a 10-storey RC frame structure. Careful ground motion selection and/or seismic demand modification is therefore required to predict such spatially distributed demands without significant bias.

This manuscript provides a critical examination of the ground motions recorded in the near-source region resulting from the 22 February 2011 Christchurch earthquake. Particular attention is given to reconciling the observed spatial distribution of ground motions in terms of physical phenomena related to source, path and site effects. The large number of near-source observed strong ground motions show clear evidence of: forward-directivity, basin generated surface waves, liquefaction and other significant nonlinear site response. The pseudo-acceleration response spectra (SA) amplitudes and significant duration of strong motions agree well with empirical prediction models, except at long vibration periods where the influence of basin-generated surface waves and nonlinear site response are significant and not adequately accounted for in empirical SA models. Pseudo-acceleration response spectra are also compared with those observed in the 4 September 2010 Darfield earthquake and routine design response spectra used in order to emphasise the amplitude of ground shaking and elucidate the importance of local geotechnical characteristics on surface ground motions. The characteristics of the observed vertical component accelerations are shown to be strongly dependent on source-to-site distance and are comparable with those from the 4 September 2010 Darfield earthquake, implying the large amplitudes observed are simply a result of many observations at close distances rather than a peculiar source effect.

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