Civil Defence is urging Bay councils to begin education of "slow-slip seismic events", which increase the risk of a large earthquake that could trigger a tsunami.
GNS had observed the events, also known as silent earthquakes, which suggested an increased risk of a 7.8 magnitude or larger earthquake in the lower North Island.
According to GNS website, the slow-slip seismic events showed tectonic stress was being relieved, and tended to occur, "just below the area of the plate interface that is 'stuck' and building up stress to be relieved in future earthquakes".
If a quake of that magnitude did happen it was likely to cause a large tsunami, posing a threat to coastal communities in much of the North Island.
Bay of Plenty Civil Defence emergency management group controller Clinton Naude spoke to the Bay of Plenty Regional Council last night about the two New Zealand slow-slips, one through Gisborne and Hawkes' Bay, and the other by Kapiti and Manawatu.
Mr Naude said the ability to monitor the slow-slip events was "very recent", which meant it was uncertain if the current movement after a large earthquake, like the recent Kaikoura quake, was normal or not.
"Both slips were moving simultaneously and at a more rapid speed."
"The Kaikoura earthquake and slow-slips have increased uncertainty and the likelihood of a subsequent earthquake. But it's still unlikely.
"It's just a good time to be prepared."
Briefings with Tauranga City Council staff were also held to discuss the increased likelihood of a large-scale earthquake affecting the Bay of Plenty.
Tauranga City Council chief executive Garry Poole said the likelihood raised questions about community readiness.
"We know that our community needs to be better prepared," he said.
The briefing followed a council meeting on Tuesday where tsunami sirens were put back on the table in Tauranga after the failure of text-alert systems to wake everyone.
Manager of emergency management Paul Baunton said at the briefing an earthquake was the first warning sign for a tsunami.
"We have excellent maps for Tauranga that you should use to plan and practise your evacuation route. The maps are based on a 14m tsunami which is a very much worst case scenario.
"It is especially important that you evacuate by foot or bicycle to avoid crippling traffic jams."
The Ministry of Civil Defence and Emergency Management asked local civil defence groups to begin preparing for tsumani educational programmes around the issue over the next six months.