Tsunami sirens around Northland will be tested on Easter Sunday - almost a month to the day after being activated for real and tens of thousands of Northlanders evacuating to higher ground.
The tests are part of Northland Civil Defence regular business as usual six-monthly testing.
Victoria Harwood, Northland Civil Defence Emergency Management Group spokeswoman, said the sirens would sound for two minutes at noon on Sunday, April 4- in conjunction with the end of daylight saving.
"..These six-monthly checks are necessary to identify any faults and keep the network in good working order," Harwood said.
The region's 205 tsunami sirens will sound for less than a quarter of the time they are usually rung during regular twice-yearly testing - as a result of the region's real-life March 5 tsunami evacuation.
"Minimising the test time to two minutes - down from the usual 10 minutes plus a further 30 seconds - is an acknowledgement that some people remain unsettled by the sound of the sirens after the events of March 5," Harwood said.
The testing will also be done later in the day than usual, due to it taking place on Easter Sunday.
Northland's indoor tsunami sirens, synced to the outdoor tsunami siren network, will also be tested at the same time.
Harwood said it was important to note that because the Easter Sunday checking was a test rather than for real, tsunami siren testing would not include sending out emergency mobile alerts (EMAs) to Northlanders' phones.
The EMAs were a major March 5 tsunami evacuation notification tool sent out to thousands of mobile phones.
"That alerting platform is tested nationally and usually at the end of each year," Harwood said.
Northland tsunami test alerts will also be sent to users of the Red Cross Hazard app, which can be downloaded for free redcross.org.nz/what-we-do/in-new-zealand/disaster-management/hazard-app/
Northland's tsunami siren network is New Zealand's biggest. The sirens are funded and owned by Far North, Whangārei and Kaipara District Councils. They are operated in a partnership which also includes the two electricity networks Northpower (Whangārei and Kaipara) and Top Energy (Far North).
Harwood said Northland Civil Defence was working towards a $4.5 million tsunami siren network upgrade with the region's first sirens installed in 2007.
She said Northland tsunami sirens would eventually reach the end of their expected life. Northland Civil Defence was working on the upgrade which would use newer tsunami siren technology. This included being able to add voice messages and required actions to go with sounding sirens.
Harwood said the newer sirens could be heard from further away, meaning fewer sirens required as replacements.
Upgrade funding was currently being progressed through Northland councils' Long Term Plan (LTP) consultation processes, she said.
Tsunamis arriving in New Zealand are classified based on how far away they begin – distant, regional or local-source.
Northlanders were part of New Zealand's biggest mass tsunami evacuation on March 5, after an 8.1 magnitude earthquake in the Kermadec Islands, about 1000km north-east of the country. A 1 to 3m tsunami was forecast.
This was a regional-source tsunami meaning it would typically take about one to three hours to reach New Zealand from its earthquake-caused starting point.
A local-source tsunami begins life on or very close to New Zealand's coast. The 2016 Kaikoura earthquake-generated local-source tsunami hit shore within 10 minutes.
Distant-source tsunamis take about a dozen hours to reach New Zealand. The 1960 distant source Chilean-generated tsunami's biggest waves took about 15 hours to arrive. This tsunami hit in Ahipara and elsewhere in New Zealand.
The Northland Civil Defence Plan ranks tsunamis among the region's major hazards. It ranks distant and regional-source tsunamis as Northland's fifth-highest ranked hazard with local-source tsunami the sixth-highest.
Harwood said Northlanders should continue to be aware of the risk posed by a real-life local-source tsunami generated on or close to the coast. This could arrive ahead of any official warnings.
"Everyone who spends time on the coast needs to know the natural warning signs of tsunami," Harwood said.
One was a strong earthquake that was hard to stand up in or lasted longer than a minute. Another was out-of-the ordinary sea behaviour, such as a sudden rise or fall and/or unusual sea noise.
To hear Northland's outdoor and indoor tsunami sirens online visit www.nrc.govt.nz/tsunamisirens
To check out if you live, work or play in a tsunami evacuation zone visit www.nrc.govt.nz/evacuationzones