Performance of Electric Power Systems in the 2010-2011 Christchurch, New Zealand, Earthquake Sequence

From late-2010 to mid-2011, Christchurch suffered a series of earthquakes and aftershocks that affected the city's power supply. The most relevant of these events occurred on 4 September 2010, 22 February 2011, and 13 June 2011. In all these events transmission level power restoration occurred rapidly within one day. Except for the second event, similar relatively minor damage led to rapid restoration of distribution-level power outages. However, extensive damage to underground cables during the February 2011 earthquake caused some outages that lasted until early March. This damage seems to be amongst the only extensively-documented such failures to date. Despite recorded strong ground shakings, damage to other power infrastructure facilities was moderate to minor. This satisfactory performance of power infrastructure is attributed to a program implemented during the decade prior to this earthquake sequence to seismically upgrade almost all unreinforced masonry substation buildings and reinforce other infrastructure elements.