A powerful earthquake measuring 5.8 magnitude on the Richter scale struck off the east coast of New Zealand on Saturday. The US Geological Survey said the tremblor struck off the east coast of the North Island at a depth of 20 kilometers (12 miles). There were no immediate reports of any injuries or damage. New Zealand is prone to earthquakes. In February 2011, a strong quake in Christchurch killed 185 people and destroyed much of the city’s downtown area.