Quake tsunami threshold changed after East Cape shake

3:55 pm on 27 April 2017

The earthquake magnitude required to trigger an automatic tsunami alert was lowered after last year's East Cape earthquake, Civil Defence says.

The 7.1 magnitude earthquake left large cracks in the sand at Rangitukia Beach near Te Araroa.

The 7.1 magnitude earthquake left large cracks in the sand at Rangitukia Beach near Te Araroa. Photo: Supplied / Ali Rewi

The change was made in response to the magnitude 7.1 earthquake last September, which caused a small tsunami and was widely felt.

Internal reviews found 31 issues with Civil Defence's response to the earthquake, including the 80-minute delay before a tsunami warning was issued.

And there have been criticisms of the way tsunami warnings were issued after the 7.8 magnitude Kaikōura earthquake last November.

Monitoring service GeoNet has since received a $3 million funding boost so it could be staffed 24/7.

Automatic tsunami alerts would now be issued for earthquakes at or above magnitude 7, down from 7.5.

And if a shake was just shy of magnitude 7, Civil Defence and GNS Science would immediately do more checking to see if a tsunami alert was needed.

Civil Defence emergency management director Sarah Stuart-Black, who discussed the change at the Seismic Engineers Society's annual conference today, said it was a fine balance between warning people and crying wolf over tsunamis.