A report of a severe earthquake in Central Otago turned out to be a "ghost quake", which was actually centred more than 1000km away.
At 9.48am yesterday, GeoNet reported a magnitude 5.3 quake had struck 30km southeast of Roxburgh, at a depth of 12km.
It quickly became apparent there was no severe shaking in Central Otago and one woman living near the supposed epicentre said: "I know nothing about it."
GeoNet, the Government-funded geological hazard monitoring agency, later said the quake had actually struck west of Macquarie Island, an Australian territory about halfway between New Zealand and the Antarctic.
The United States Geological Survey, which is better equipped to detect seismic activity outside New Zealand’s borders, reported a 6.1 magnitude quake struck 28km west of the island at a depth of 10km, at 9.46am.
GNS Science duty seismologist Caroline Little said "ghost quakes" happened every so often.
"More often we get this from earthquakes halfway up to Tonga and our system pulls them in and puts them in close to Gisborne but this is the opposite case," Ms Little said.
Ghost quakes happened because the system was geared towards picking up earthquakes in New Zealand.
"With earthquakes far off the coast our [equipment] can still record all that shaking but it’s very poor at getting a location because we don’t have seismographs surrounding the earthquake to confine where it is."
The quake was reported through its automatic location system and was corrected once a seismologist looked at the data.
GNS would look at "tweaking" the system so such occurrences did not happen as often but would be careful not to alter it in a way that risked it missing New Zealand earthquakes.
Ms Little said she would be "surprised" if the few people who reported feeling the quake in New Zealand had actually felt it.
