An earthquake with a magnitude of 7.4 struck 91 km (57 miles) north-northeast of the city of Christchurch, New Zealand just after midnight (1102 GMT Sunday), the US Geological Survey said. Christchurch is the biggest city on New Zealand’s South Island. A 6.3 quake there in February 2011 killed 185 people and caused widespread damage.The US Pacific Tsunami Warning Center said there was no tsunami threat from Monday’s quake.