February quake size revised upwards

7:01 am on 4 April 2011

GNS Science has upgraded the severity of the Christchurch earthquake and its aftershocks on 22 February.

GeoNet Project director Ken Gledhill says the quake at 12.51pm, initially registered as magnitude 6.3 - was actually magnitude 6.343.

An aftershock almost 15 minutes later has been upgraded to magnitude 5.8 from 5.7.

Dr Gledhill says another aftershock at 2.50pm that day is now a magnitude 5.9 - up from the original assessment of 5.5.