The source of booms heard in Whanganui on Wednesday night remain a mystery, but some seismic activity has been recorded around the same time.
A small burst of energy was recorded in Whanganui at the same time the mysterious noises were heard in the region, GNS Science seismologist John Ristau said.
At around 10.15pm "for a few seconds, there was a bit of energy a bit above the background noise levels".
It seemed "more than just a coincidence" the activity took place at the same time people reported hearing the noises in Whanganui, Dr Ristau said.
The activity was not caused by an earthquake, he said, and he was not sure what had caused the noises or the seismic activity.
"Maybe [it was] some heavy machinery, maybe a train went by, I don't know."
The incident reminded him of the 'Seneca Guns', Dr Ristau said, a phenomenon where mysterious noises were heard around the United States.
The cause of those noises also remain a mystery.
What are the 'Seneca Guns'?
1. The term 'Seneca guns' is just a name, not an explanation. It does not tell us anything about what causes these noises and shakings.
2. The name comes from a short story by James Fennimore Cooper written during the 1800's about booms heard on the shores of Lake Seneca and Lake Cayuga in New York State.
3. The name has been applied to similar noises along the coasts of North Carolina, South Carolina, and Virginia.
4. Similar booms are called Barisol guns in coastal India.
5. The thing that comes closest to matching all of the observations is sonic booms from military aircraft, but no official explanation has been found.
What the Seneca Guns are not:
Tidal waves, landslides, tectonic plates shifting, new faults forming or meteor explosions.