A pumice raft spotted by a Royal New Zealand Air Force crew has pointed to a possible major undersea eruption somewhere in the Tonga-Kermadec volcanic arc.

Monday's 7.8 quake was bafflingly complex in some ways, but simple in others. Science reporter Jamie Morton delved into the data to look at what we know so far.

The probability of another 7.0-plus quake striking have fallen further, GeoNet reported today, but large aftershocks are still likely across a large area of New Zealand.

Scientists have revealed the extent of uplift on the South Island's northeastern coast - observing that in some places the land was raised by two metres.

The probability of another plus-7 magnitude quake within the next month has fallen - but the chances of multiple large aftershocks remains a virtual certainty.

Science reporter Jamie Morton talks to GNS Science earthquake geologist Dr Rob Langridge, who has been on the ground mapping damage around Marlborough.

What's it like to be part of the team at GNS Science when a big quake hits? Seismologist Dr Helen Anderson shares an insight.

It appears our volcanoes have slept through the Kaikoura quake, with monitoring equipment showing only a few tremors over recent days.

The probability of another huge quake over magnitude 7 in the next 24 hours has been put at 4 per cent - but at 14 per cent in the next week and 22 per cent across the next 30 days.

Scientists are trawling through data to see how New Zealand has shifted following the latest quake.

Science reporter Jamie Morton talks to GNS Science earthquake geologist Dr Rob Langridge about a renewed effort to catalogue a nationwide web of active faults threatening New Zealand.