Violent aftershocks rattled residents of Christchurch today as parts of the city re-opened for the first time since New Zealand's biggest quake in nearly 80 years. The official geological monitoring service GeoNet reported more than a dozen aftershocks overnight, prompting authorities to evacuate 70 people sheltering in temporary accommodation in a high school. Christchurch mayor Bob Parker said the aftershocks were further damaging weakened buildings in the South Island city of 3,40,000 people.