Great Barrier Island residents wait on higher ground following a tsunami warning on March 5. Photo: Bridget Cameron/Getty Images

Transferring tsunami warnings to GNS Science might speed them up, an official report suggests. David Williams reports

Effective tsunami warnings are being “impeded” because the National Emergency Management Agency doesn’t have a 24/7 duty team, an official review has found.

March 5 was unique for emergency officials responding to tsunami warnings from three offshore earthquakes on the same day – a 7.3 magnitude shake at 2.27am from on the Hikurangi fault, north-east of the North Island’s East Cape , and two near the Kermadec Islands, north east of New Zealand, at 6.41am and 8.28am. The two Kermadec quakes were magnitude 7.4 and 8.1.

The latter two quakes were handled reasonably well. But after the Hikurangi quake, it took NEMA 61 minutes to issue a national warning of a tsunami threat to land and sea – and another eight minutes – at 3.36am – to post an “evacuate immediately” order.

The threat was downgraded at 5.02am and the national advisory cancelled at 6.01am – only to be followed 40 minutes later by the first Kermadec quake.

(Waves of a maximum amplitude of 35cm were recorded at Lottin Point, East Cape, and up to 20cm at Great Barrier Island. Waves at Great Barrier later lifted to up to 40cm because of overlapping from the Kermadecs quakes. Unusual surges lasted for days.)

There was confusion in the Bay of Plenty, with the main Civil Defence page telling people to get out, while authorities posted to Facebook saying there was no threat. A map of at-risk areas didn’t emerge for hours.

NEMA’s response was generally efficient and effective, says its review, posted on its website on Tuesday. It was helped by improvements such as tsunami warnings being sent to mobile phones.

But advice to the public needs to be faster, the report concludes, and what might help is improving the distribution of agency responsibilities.

Our national agency for emergency management isn’t staffed around the clock – an issue identified years ago. Photo: Lynn Grieveson

Right now, Crown research institute GNS Science is responsible for assessing tsunami threats, but NEMA is responsible for issuing warnings. The arrangement “adds layers of complexity and causes delay”, the NEMA report says.

GNS’s national geohazard monitoring centre is staffed around the clock, but NEMA’s duty team, of eight people, isn’t “dedicated, centralised and ‘awake’ 24/7”. This is a known problem, which appears to be a victim of Government foot-dragging.

A 2018 advisory group report said without an awake duty team, NEMA’s warnings and ability to establish a response would be delayed. The following year, in the Cabinet paper agreeing to establish NEMA, money was committed to address issues with on-call staff having to be woken up for an emergency.

Two years later, a review of duty arrangements is still underway – alongside work by GNS Science to improve tsunami monitoring and warning. The NEMA report into March 5 says options for speeding up the response includes transferring the responsibility for tsunami warning to GNS Science, and/or a dedicated 24/7 (awake) monitoring, alerting and warning capability for NEMA.

The report notes threat assessments, especially for near-shore quakes, aren’t an exact science – that the series of quakes on March 5 “proved to be complex for scientists”.

At 2.42am on March 5, NEMA issued a message saying the Hikurangi quake was being assessed. Thirteen minutes later GNS provided advice a land threat was possible. But before NEMA could issue a tsunami warning, the advice reversed. At 3.06am, GNS told NEMA there was no land threat.

“The difference between a land threat and a beach and marine threat is quite significant, especially during the middle of the night,” the NEMA report says, noting only a land threat requires an “emergency mobile alert”.

As NEMA’s duty team prepared a response using a “different template”, GNS Science did another about-face, and advised a land threat was possible. “The changing science advice delayed the issuing of the warning.”

The response report also noted GNS was the only agency with the necessary depth and breadth of scientific knowledge to make tsunami threat assessments.

A warning issued at 3.30am to emergency authorities (which wrongly said the quake occurred at 2.58am) included a tsunami forecast map. Over the course of the day, 21 mobile alerts were sent by NEMA and regional Civil Defence groups – the first time a significant number of messages were sent over wide geographic areas since the system was introduced in 2017.

About 200 Tsunami warning sirens were sounded in Northland, where there’s patchy mobile phone coverage – so Civil Defence in the region considers sirens are important in a tsunami response.

NEMA’s report, however, says they’re not effective or reliable, and can cause complacency. The most reliable warning is the quake itself.  

“Local-source tsunami, where the earthquake has occurred close to New Zealand’s coastline can arrive within minutes at areas closest to the shore and there may not be time to issue an official warning before the first wave arrival, nor even activate the sirens.”

Natural warning signs are underscored by the “Long or Strong, Get Gone” public education campaign. An advertising blast of the campaign from March 9, which had been planned for April and May but was brought forward, costing $340,000.

David Williams is Newsroom's environment editor, South Island correspondent and investigative writer.

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