A 7.0-magnitude earthquake has struck off New Zealand's South Island. The US Geological Survey has said the epicentre was 55 kilometres north-west of Christchurch at a depth of 12 kilometres. The Police said there had been widespread damage to buildings and roads as well as power cuts. Two men were seriously injured by falling masonry and glass. A state of emergency has been declared in Christchurch, New Zealand's second largest city with a 386,000 population. New Zealand lies at the southern end of the so-called Pacific Ring of Fire and above an area of the Earth's crust where the Pacific Plate converges with the Indo-Australian Plate.The country experiences more than 14000 earthquakes a year of which only around 20 have a magnitude in excess of 5.0. The last fatal earthquake was in 1968 when a 7.1-magnitude tremor killed three people on the South Island's western coast.