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(A)(B)▲▲Figure 12. A) Damage to a residential house in south Kaiapoi that underwent foundation failure due to lateral spreading and liquefactionin the 2010 Darfield earthquake. B) Additional damage after the 2011 Christchurch earthquake.(A)(B)▲ ▲ Figure 13. A) Liquefaction at a park adjacent to Courtenay Lake, south Kaiapoi, following the September 2010 earthquake. B)Re-liquefaction during the February 2011 earthquake resulted in sand boils being ejected through existing cracks, but ground distortionwas minor.aftershocks of the 2010 Darfield earthquake has been reported(Cubrinovski and Orense 2010). Therefore, there is a possibilitythat the width of the crack was more than 1.6 m before theFebruary 2011 earthquake and the impact of the earthquake tothis area was minor. No other remarkable additional damageto residential houses/properties was observed in south Kaiapoi.After February 2011, most of the sand boils in areas closeto the waterways were observed at existing/repaired crackscaused by the 2010 earthquake. Aside from the lower intensityof ground shaking in Kaiapoi, it is possible that the excess porewater pressure generated by the earthquake motion could havebeen dissipated easily through the existing cracks and thereforethis earthquake did not induce significant ground deformation(Figure 13).On the other hand, a more pronounced liquefaction wasobserved in residential houses/properties in north Kaiapoi,although relatively minor compared to that after the 2010Darfield earthquake. Figure 14 compares the settlement of atwo-story house due to liquefaction. The slope in front of thegarage was originally uphill, but it became downhill after the2010 Darfield earthquake as a result of more than 50 cm ofground subsidence. This house suffered an additional 15 cmsubsidence following the 2011 earthquake. The narrowinggap between the roof and the head of a member of the reconnaissanceteam can be recognized from the figure. Althoughthe team members appearing in the photos are different, theirheights are almost the same.914 Seismological Research Letters Volume 82, Number 6 November/December 2011