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(A)(B)▲▲Figure 8. Damage to a river embankment near the Avon Rowing Club: A) 2010 earthquake; and B) 2011 earthquake.(A)(B)▲▲Figure 9. Cracks observed in Porritt Park: A) 2010 earthquake; and B) 2011 earthquake.quake triggered liquefaction of the loose uncompacted fill,resulting in ground settlement and lateral spreading. Ejectedsands filled up the whole neighborhood, as thick as 30 cm insome areas (Figure 10A). Following the 2011 earthquake,Bexley was again one of the worst-hit areas in terms of liquefaction-induceddamage. Massive amount of sands were againejected and deposited around houses (Figure 10B). The massivesand boils ejected from underground caused differentialground settlements, resulting in the tilting of many houses.Sand boils were also observed in the swamps of Bexley wetlands,indicating that the ground below the swamp also underwentliquefaction.KaiapoiThe township of Kaiapoi is located in the northeastern end ofthe Canterbury Plains, about 20 km north of Christchurch(Figure 1). The Kaiapoi River, which cuts through the centerof the town, joins the Waimakariri River on the eastern edge ofthe town and flows to the sea. In terms of liquefaction duringthe 2010 earthquake, Kaiapoi was probably the worst-hit area,with many residential houses, several commercial buildings,and other infrastructure facilities suffering damage due to lateralspreading, ground subsidence, and differential settlement.Investigations of old maps by Wotherspoon et al. (2010)showed that that much of the most significant liquefactiondamage in and around Kaiapoi during the 2010 Darfield eventoccurred in areas where river channels had been reclaimed orin old channels that have had flow diverted away. The highlymodified nature of the Waimakariri River and its proximity toKaiapoi meant that some of these reclaimed areas overlappedregions that have since been developed as the town has grown,as shown in Figure 11.Following the 2011 earthquake, re-liquefaction occurredin Kaiapoi; however, because of the farther epicentral distance,the impact of liquefaction was minor compared to thatobserved in September 2010. The peak ground accelerationsrecorded in Kaiapoi during the 2010 and 2011 earthquakeswere 0.36 g and 0.20 g, respectively. A comparison of the distributionof liquefaction in Kaiapoi during the two events showedsmaller liquefaction zones in 2011. Areas where re-liquefaction912 Seismological Research Letters Volume 82, Number 6 November/December 2011