The first quake - magnitude 5.8 quake, 8km deep and centred 20km north east of Lyttelton - struck at 1.58pm, GeoNet said. It was followed by a magnitude 5.3 quake at 2.06pm, a magnitude 6 quake - the largest - at 3.18pm and a 5.0, just 10 km deep, at 4.50pm.