It's unknown whether New Zealand could suffer the kind of quake that rocked Mexico last year - a tremor that's got geologists baffled.
The magnitude 8.2 Chiapas earthquake struck in September 2017. A new study has found it shouldn't have happened, according to current understandings of how earthquakes occur.
The quake was so strong, it split the 60km-thick tectonic plate in two right down the middle.
"We don't yet have an explanation on how this was possible," said study leader Diego Melgar of the University of Oregon.
New Zealand sits where the Pacific and Australian plates meet, on the Pacific Ring of Fire. The Pacific plate is subducting under the Australian - just like how the Cocos ocean plate is diving under the North American plate at the site of the Chiapas quake.
Most quakes happen where plate boundaries meet and rub up against one another.
"One of the unusual aspects of the Chiapas earthquake was that type of earthquake (what are called in-slab earthquakes as they occur within the subducting slab or plate) occurring in a warm, buoyant plate - they're more common in colder, denser plates," Dr John Ristau, GNS seismologist, told Newshub.
Older plates which have lost much of their heat become brittle, and more likely to snap. The Cocos plate is only 23 million years old, but the Pacific plate is at least 120 million years old.
But this doesn't mean we're more or less likely to experience a similar quake.
Earthquakes commonly occur within the subducting Pacific Plate around the North Island," said Dr Ristau - for example the 2007 Gisborne quake which measured magnitude 6.7, and the 6.2 Eketahuna quake of 2014.
"The difference is they were smaller and did not break through the entire thickness of the plate, rather just a portion of it.
"Whether they could be as large as the Chiapas earthquake is unknown. Prior to Chiapas we would not have thought an earthquake like that could occur in that region. Normally in-slab earthquakes are not that large, and the Chiapas earthquake may have been a perfect storm of geologic/tectonic conditions to result in one that large."
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He says the infamous Christchurch quakes and the one that rocked Kaikoura - measuring 7, 6.3 and 7.8 respectively - were unusual in their own way, but "much different" to Chiapas.
"They did not occur within the subducting slab, rather they were in the crust above the slab."
The Kaikoura quake had more than 20 separate ruptures - one of the most complex quakes ever seen.
"But they don't help to shed light on a Chiapas-type event," said Dr Ristau.
Nearly 100 people were killed in the Chiapas quake, which struck just offshore. The second large Christchurch quake, which struck on February 22, 2011, killed 185 people.
Newshub.
