Seismologists in New Zealand said on Friday there is a high possibility of more powerful aftershocks after the 7.8-magnitude quake rocked South Island on Monday, killing two people.
The tremor struck 16km underground near Hanmer Springs, some 91 km northeast of Christchurch in the South Island, and was felt across the country. The earthquake was of a greater magnitude than the devastating tremors that struck Christchurch in 2010 and 2011.
The official GeoNet science agency said the earthquake permanently changed the region's geography as the land moved up to 11 metres (36 feet) along the many faultlines in the South Island disaster zone.
The seabed was also pushed by the quake by as much as two metres along a 110 kilometre (70 mile) stretch of coastline including Kaikoura, a tourist town. GeoNet said at least four faults were ruptured by the quake. It said the quake was "clearly... one of the most complex earthquakes that has ever been observed".
Since Monday, the region has been experiencing more than 2,000 aftershocks and the agency added that the residents should be prepared for more major shakes in the coming weeks.
It said that the current probability of 6.0-magnitude quakes and above was "about 100 times larger than what we would normally expect".
The authorities also warned about several dangerous temporary dams which were created by some rain-swollen rivers, blocked by quake debris.
"Landslide dams can break quickly, and release large volumes of water and sediment as a flood wave," Sarah Stuart-Black, the Civil Defence director told AFP.
New Zealand sits on the highly seismically active zone "Pacific Ring of Fire" and experiences frequent volcanic eruptions and earthquakes.
Check out some more photos of the disastrous earthquake in New Zealand: