Dr Hamish Campbell, Te Papa’s geologist in residence from GNS Science, shares his experience witnessing the green lights in the sky following Sunday night’s earthquake.
Green sheet lightning
I was driving home to Wellington from Auckland late on Sunday night after having had dinner in Taupo with Dinah and our children Niamh and Riley.
Petrol and coffee in Bulls just before midnight and then onwards beyond Sanson along that long straight stretch of road heading southwest.
There was a lovely full moon and an almost clear sky with only a thin veil of wispy high cloud.
Suddenly the sky lit up on the horizon with what I would describe as green sheet lightning. Weird stuff…and no rain clouds evident.
It did not last long, a matter of seconds. It was directly ahead of me, far to the southwest and high in the sky, widely spread and seemingly moving from west to east.
Time went by, and I stopped thinking about it.
I continued in my radio-free car and arrived at my home in Ngaio at about 1:15am. Straight to bed…only to be disturbed by my mobile.
It was a text from my daughter Saskia asking: ‘Are you okay Dad?’. Such a strange question at that hour of the night from Osaka! I replied: ‘Of course!’.
So it was that I learnt of the magnitude 7.5 Kaikoura earthquake from Saskia in Japan – there is nothing like social media.
And it then dawned on me that the green lightning that I had observed was almost certainly an atmospheric effect caused by the earthquake.
I had SEEN an earthquake. Yay!
The phenomenon is real
As a geologist, over the years I had heard of atmospheric effects associated with earthquakes.
Various theories abound including a gas release explanation (yeah right!), an instantaneous ion discharge effect that translates into electrical light emission in the upper atmosphere (much more likely), and so on.
Poorly understood and commonly poo-pooed as an illusion, I can now vouch first hand for this phenomenon being real.
Furthermore, my colleagues at GNS Science, Sarah Milicich and Wendy Saunder, also witnessed this green light phenomenon from their homes in Wellington.
What to expect now
This earthquake is the largest recorded in New Zealand since the magnitude 7.8 Dusky sound earthquake in 2009.
However, the Kaikoura earthquake was much more widely felt and more damaging because of its location in central New Zealand.
According to my colleagues at GNS Science and our surveillance arm GeoNet, the aftershock sequence experienced so far is considered to be normal for an earthquake of magnitude 7.5. The frequency is diminishing as expected.
However, the possibility of a large aftershock of between 6.0 and 6.9 within the next 30 days is very likely.
There is also a possibility of the Kaikoura earthquake sequence triggering an earthquake that is of greater magnitude than magnitude 7.5 within the next 30 days but this is considered very unlikely.
As for Wellington, there is no evidence of an impending large earthquake of similar size to the Kaikoura earthquake at this stage but we cannot rule this out.
We cannot make a calculation to predict this but the chance of a further shock in the Wellington area has increased somewhat since the Kaikoura earthquake.
How Te Papa held up
Fortunately all Te Papa’s staff came through the earthquake unharmed. The quake has not had any impact on the building’s structure and the seismic restraining work carried out at the museum in recent years had protected the collections.