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Location of structures illustrated insubsequent figures.Geomorphic featureModerate to severeliquefaction zone indicatedwith black shading.Avon RiverChristchurch Cathedral▲▲Figure 4. Preliminary liquefaction map indicating zones of weakness and locations of buildings discussed in the paper.(A)(B)▲▲Figure 5. Representative areas of: A) moderate liquefaction (7 March 2011; S43.52791 E172.63653), and B) severe liquefaction withinthe CBD principal liquefaction zone (4 March 2011; S43.52604 E172.63839).relatively extensive areas and volumes of sediment ejecta (Figure5). There were also areas of low manifestation or only traces ofliquefaction, but also pockets of severe liquefaction with verypronounced ground distortion, fissures, large settlements, andsubstantial lateral ground movements. This non-uniformityin liquefaction manifestation reflects the complex and highlyvariable soil conditions even within the CBD principal liquefactionzone. Survey maps of Christchurch dating back to thetime of early European settlement (1850s) show a network ofstreams and swamps scattered across this area (Archives NewZealand 2011).The north extent of the zone, which is shown by the thicksolid line in Figure 4, is a clearly defined geomorphic boundaryrunning east-west that was delineated by a slight change in elevationof about 1 m to 1.5 m over an approximately 2 m to 10 mwide zone before the earthquakes. After the 22 February event,Seismological Research Letters Volume 82, Number 6 November/December 2011 897