The Civil Defence response to today's 7.1 magnitude earthquake will be reviewed to see if anything could have been done differently.
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Questions are being asked on social media about why it took Civil Defence almost 90 minutes to send out a text alert.
The Ministry of Civil Defence sent out its first national advisory at 5.10am - about 40 minutes after the quake hit.
A potential tsunami threat notice was not issued until 5.33am and a request for an emergency broadcast was not made until 5.58am.
Minister for Civil Defence Nikki Kaye said the ministry will review its response.
She said it already has a project underway looking at current processes for national warnings and public alerting, and this includes looking at the timeliness of alerts.
NZ:Timeline of earthquake response
4.37am earthquake strikes
4.41am - The Ministry of Civil Defence & Emergency Management receives initial notification of a magnitude 6.3 earthquake from GNS Science
4.53am - GNS upgrades quake to a 7.1
These earthquakes did not meet the threshold for automatic issuing of a potential tsunami threat, ministry says
5.10am - Ministry issues an earthquake notification
Pacific Tsunami Warning Centre finds no tsunami threat in their initial assessment
5.33am - Ministry issues national advisory for a potential tsunami threat. Says it's proactive while awaiting confirmation from scientists
5.58am - A tsunami warning is issued
8.30am - Cancellation message sent at 8.30am.