A 7.2 magnitude earthquake rocked New Zealand's second largest city Christchurch early Saturday, causing widespread damage including the collapse of some buildings and power outages, witnesses and the US geological survey said. A strong earthquake rattled New Zealand at 4:35 am local time Saturday morning. The USGS posted a magnitude of 7.2. The quake was felt through much of New Zealand's South Island where Christchurch is located on its east coast, the Post said. There was no widespread threat of a tsunami, according to the Pacific Tsunami Warning Centre.