A 4.2-magnitude aftershock struck near New Zealand's second city of Christchurch Monday morning, six months after the devastating 6.3-magnitude earthquake on February 22 left at least 181 people dead. The quake struck at 8: 38 a.m. local time, and was centered 10 km southeast of the port of Lyttelton at a depth of 10 km. The government's GNS Science research institute said the quake was widely felt in Christchurch, and strongly in some areas.