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30 cm17 cm30 cmFoundation beam▲ ▲ Figure 15. Building on pile foundations in area of severe liquefaction showing large settlement of the surrounding soils relative tothe foundation beams (4-6 March 2011; S43.526575 E172.638668).of liquefaction without significant differential settlement andbuilding damage.Contrasting Performance of a Pile-SupportedStructure—Kilmore AreaSeveral pile-supported structures were identified in areasof severe liquefaction. Although significant ground failureoccurred and the ground surrounding the structures settled,the buildings supported on piles typically suffered less damage.However, there are cases where pile-supported structureswere damaged in areas that underwent lateral spreading nearthe Avon River. In other cases, such as the building shown inFigure 15, which is located approximately 200 m to the eastfrom the Town Hall, the ground-floor garage pavement washeavily damaged in combination with surrounding grounddeformation and disruption of buried utilities. The settlementof the surrounding soils was substantial, with about 30 cm ofground settlement on the north side of the building and up to17 cm on its south side. The first-story structural frame of thebuilding that was supported by the pile foundation with strongtie-beams did not show significant damage from these liquefaction-inducedground settlements.Across from this building to the north is a seven-storyreinforced concrete building on shallow spread footing foundationsthat suffered damage to the columns at the ground level.This building tilted toward the southeast as a result of approximately10-cm differential settlement caused by the more severeand extensive liquefaction at the south-southeast part of thesite. It is interesting to note that in the vicinity of this building,the site contained areas that liquefied during the 4 September2010 earthquake. Following the extensive liquefaction in the22 February 2011 event, there was also significant liquefactionin some areas during the 13 June 2011 earthquakes.Having all of this in mind, these two buildings provideinvaluable information on the performance of shallow foundationsand pile foundations in an area of moderate to severe liquefactionthat induced uneven ground settlements. Extensivefield investigations are planned to document the ground conditionsin detail at these sites.Presence of Shallow Gravelly Soils—Victoria SquareNear Victoria Square, the liquefied zone was composed predominantlyof relatively deep loose sand deposits that transitionedrelatively sharply into a zone where gravelly soil layersreach close to the ground surface. Shallow foundations (spreadfootings and rafts) for many of the high-rise buildings in thislatter area are supported on these competent gravelly soils.However, the ground conditions are quite complex in the transitionzone, which resulted in permanent lateral movements,settlements, and tilt of buildings either on shallow foundationsor hybrid foundation systems, as illustrated in Figure 16.Immediately to the north of these buildings, the liquefactionwas severe with massive sand ejecta; however, approximately100 m and further to the south where the gravels predominate,there was neither evidence of liquefaction on the groundsurface nor visible distress of the pavement surface. Again, itappears that the ground and foundation conditions have playeda key role in the performance of these buildings, which thereforehave been selected for in-depth field investigations.Lateral Spreading—Avon RiverLiquefaction-induced lateral spreading was evident within theCBD along the Avon River in the liquefied zone, and the horizontalstretching of the ground adversely affected several buildings.Detailed measurements by ground surveying conductedat about 10 transects on the Avon River within the CBD afterthe 22 February earthquake indicated that at several locationsthe maximum spreading displacements at the banks of theAvon River reached about 50–70 cm, whereas at most of theother locations the spreading was on the order of 10 cm to 20Seismological Research Letters Volume 82, Number 6 November/December 2011 903