Christchurch's inner city suffered further damage in Tuesday night's powerful aftershock.
GNS Science initially said the jolt, felt at 10.30pm, was a 5.3 magnitude aftershock, near Akaroa. That was later assessed as 5.4 and much closer to the city, 10km southwest and 8km deep.
The quake was felt widely across the Canterbury region, as far south as Dunedin and as far north as Mt Thomas.
In the following hours, up to 5pm Wednesday, there were at least 18 aftershocks strong enough to register on Geonet's website. The largest measured 4.7.
The Canterbury Earthquake Recovery Authority (CERA) says more cracks have appeared, masonry has fallen and windows have broken in the indicator buildings in the red zone.
Power was cut in a number of suburbs, including Ilam, Halswell and Avonhead, but Orion says electricity was restored at about 2am.
Significant earthquakes that started on 4 September last year and included the fatal quake on 22 February have left parts of the city in ruins and the future of others up in the air.