Napier City Council chief executive Wayne Jack has responded to criticism of Hawke's Bay Civil Defence after a tsunami alert in the early hours of Monday morning.

People took to social media this week to complain about mixed messages received as to the tsunami risk, and also that warning sirens had not been activated in the Napier red zone coastal areas after the 7.5 quake that caused devastation in the Kaikoura region, and significant damage to the Wellington CBD.

Former civil defence planner Joel Benjamin raised concerns about the lack of sirens, and the timing of warnings to evacuate, particularly in the Westshore and Ahuriri area.

In his capacity as the chair of the Chief Executive Group for HB Civil Defence, Mr Jack echoed comments made by local civil defence group controller Ian Macdonald that neither Hastings nor Napier actually had tsunami sirens, rather they had public alerting systems designed to warn people to seek further information.

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The public alert sirens were not used at Westshore because of the low number of houses needing to evacuate, and to avoid a mass evacuation, which could have been life-threatening in itself, Mr Jack said.

During Monday's event, he said the Hastings stinger (a vehicle carrying a mobile siren) allowed customisable messages to be played for Haumoana and Te Awanga, and the Napier Civil Defence ute and its speaker system was deployed in the same way at Westshore and Ahuriri.

"The police were used to evacuate the residents of Westshore whose properties were in the red zone and there are very few of these, all of whom were contacted according to information we received. Freedom campers were evacuated successfully with the use of the CD ute as described," Mr Jack said.

Evacuation decisions followed national advice and were not delayed, he added.

"National advice of a tsunami threat to Hawke's Bay was received at 1.30am - this national information feeds into a model run by the Hawke's Bay Regional Council.

"The initial advice from the HBRC, purely on the location and magnitude, was received at 2am for the red zone only, and national advice on potential wave heights was first received at 2.20am."

At 2.30am, the HBRC produced information that confirmed the red zone evacuation decision, he said.

At 3.08am, a .2m surge was first detected at the Napier Port tidal buoy.

He said as soon as the national information was changed from "no threat" to a "marine and land" threat the decision was made to begin evacuating, although in Haumoana and Te Awanga, people had already begun doing so themselves.

In the future, he said HB Civil Defence would continue to reinforce the "long and strong get gone" message, a Red Cross public alerting app would be introduced, and that nationally cellphone broadcasting was being investigated.

As for sirens, he noted that around the world their use had been proven ineffective.

"In Japan in 2011 they contributed to loss of life as people waited for the siren rather than responding to the natural signs."