Christchurch is still being rocked by aftershocks 15 hours after a 7.1 magnitude earthquake which caused widespread damage.
At 4.55pm the city was hit by its biggest aftershock - a 5.4 magnitude shake centred about 10km southwest of Darfield at a depth of 10km - since the 4.35am shake which has left thousands without power and water as night falls.
Since 4.30pm the city has experienced at least seven major aftershocks, including a 4.3 magnitude quake focused only 10km southwest of Christchurch at 6.54pm, according to the GeoNet website.
By 10pm tonight there had been several further strong aftershocks.
Prime Minister John Key, who saw first-hand the devastation across Christchurch this afternoon, said it was a miracle more people weren't killed.
"This is a very, very sizeable earthquake in a very populated part of New Zealand."
Eighty police officers from Auckland will be flying in to assist with general duties and recovery in Christchurch tonight