A strong earthquake of 7.4 magnitude hit New Zealand, just 4 miles (7 km) southeast of Christchurch, in the middle of the night local time, the US Geological Survey said on Friday.
There were no immediate tsunami warnings. USGS earlier said the quake measured 7.3 magnitude.
The centre of the quake was 41miles (66km) deep and it struck at 1635 GMT.
Christchurch, on the east coast of the South Island, is New Zealand's second-largest city with a population of about 342,000 people.
"No destructive widespread tsunami threat exists based on historical earthquake and tsunami data," the Pacific Tsunami Warning Centre said.
