GNS Science is blaming teething problems with a new earthquake alert system for two false reports of tremors off the North Island's west coast on Thursday morning.
The automated system reported two quakes hitting west of Auckand and off Opunake.
The quakes, supposedly measuring 6.4 and 5.6 in magnitude, were in fact near Oxford in Canterbury and measured 3.7 and 2.7.
GNS Science seismologist Martin Reymers says a quake near the Kermadec Islands north of New Zealand was happening at the same time as the ones in Canterbury, giving the wrong location.
"This is the first time that this has happened and it's got the first location so badly wrong.
"It's a quirk of the timing of the earthquake - separate earthquakes at different parts of the country and the system can't actually sort those out. It takes a while."
Mr Reymers says it might be worth GNS delaying sending preliminary alerts until it gets an earthquake's precise location and size.
GNS says initial alerts sent from the Geonet Data Centre can be very preliminary and subject to change.