New Zealand's South Island was shaken by an earthquake measuring 7.4 on the Richter scale on Saturday. There were no immediate reports of casualties. The quake happened at 4:35 a.m. local time (1635 GMT Friday) and was centered 30 km northwest of South Island's largest city of Christchurch. It was at a depth of 33 km, the New Zealand Institute of Geological and Nuclear Sciences reported. It was also felt in other parts of the South Island and in Wellington. Helena Wang, a resident in Christurch, told Xinhua that the quake was strongly felt in the city. The quake rocked her house terribly, and some books fell to the ground from the book shelf. She said electricity was out in her house and there were also aftershocks. Some residents have left their house and stayed outdoors. A spokesperson with the lines company Orion said power is out in most of Christchurch because of the extensive damage there. The spokesperson said sewer lines and water pipes have ruptured, and whole substations are offline. Christchurch police said part of Avonside Drive was ripped up and had to be closed to traffic. Structural damage to houses and broken glass have been reported throughout Christchurch. Police said damage and power outages have been experienced as far afield as Dunedin. A spokesperson for the Civil Defense Headquarters said staff will decide soon whether to activate the national crisis center. The spokesperson said information is still coming in about the earthquake, which is being assessed, and a decision will be made soon. 