A series of big earthquakes in less than 24 hours could have been caused by seismic waves travelling along fault lines and triggering ruptures.
All were along the 'Ring of Fire' that stretches around the Pacific from New Zealand to Chile through Indonesia, Japan, and California, in which 90 per cent of quakes happen.
Earthquakes in New Zealand, Japan, Vanuatu, Indonesia, Tonga, Taiwan, and Papua New Guinea over past 24 hours could be caused by seismic waves travelling along fault lines
Reports from GeoNet (pictured) showed the second quake being felt strongly around Wellington and the Cook Strait
There was also a big earthquake in Mexico that killed more than 230, but despite the country falling in the 'Ring', experts ruled out a connection to the other quakes.
Seismologists admitted the cluster of quakes, along with others near Tonga (5.0), Taiwan (5.3), and Papua New Guinea (5.2), on the same day was 'unusual'.
'It is unusual, there's no doubt about that, it's been really busy,' University of Melbourne's Gary Gibson told Daily Mail Australia.
'I must say these unusual clusters happen fairly often and it seems they are not totally random, we just don't know why.'
A 6.1 magnitude earthquake struck overnight off the coast of Japan
A similar earthquake back in 2011 killed 15,894 people and injured 10 more when a tsunami, landslides and fires broke out as a result. But experts are predicting today's quake should pass by without causing any harm
Phil Cummins at Geoscience Australia and the Australian National University suggested seismic waves cascading along fault lines could be responsible.
He said waves could also jump between nearby fault lines and continue moving, triggering imminent earthquakes at rupture points.
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'The waves that are excited by the earthquakes might rattle or disturb some distant faults that are close to rupture already,' he said.
Professor Cummins said seismic waves couldn't create earthquakes by themselves, but could bring forward ones already about to happen.
Locals living near Mount Agung volcano in Bali were seen evacuating their homes following a 5.7 magnitude earthquake nearby
Vanuatu, which has a population of 270,000, is made up of 80 nations scattered across 1,300 kilometres of ocean and experienced a 6.4 magnitude earthquake early on Wednesday
'These are earthquakes that would almost certainly have happened very soon,' he said.
Like Mr Gibson, he said earthquakes seemed to cluster in time but there was well-established explanation why, only theoretical possibilities.
Professor Cummins also couldn't rule out the same mechanism could provoke another significant earthquake in coming hours or days.
A person is rescued from the debris in Mexico City after the devastating earthquake on Wednesday that killed more than 230 people
Mexico was devastated by a 7.1 magnitude, killing more than 230 people and leaving hundreds more trapped underneath collapsed buildings
However, both scientists ruled out any link to Wednesday's twin earthquakes in Mexico, which killed more than 230 people as they were too far away.
Mr Gibson said the first Mexican earthquake could in theory have triggered the other by creating a stress field – but they would need to be at most 200km apart.
'It is possible for earthquakes to affect a stress field and trigger more quakes, but those earthquakes would have had to be fairly imminent in the first place,' he said.