Relevant Links:

NZ Earthquake Incidents GIS:
http://eqviewer.co.nz/

NZ Ministry of Civil Defence:
http://www.civildefence.govt.nz/

Environment Canterbury - Earthquake Page
http://canterburyearthquake.org.nz/

Google
http://www.google.com/crisisresponse/christchurch_earthquake.html

Twitter Tags:
#eqnz ( picked up by GIS and MoCD above)
#chch ( monitored by MoCD above)
#nzeq