A combination of earthquakes and strong wind have triggered skifield alarms on Mt Ruapehu today – but operators say there's no cause for concern.
GeoNet reported a series of earthquakes around Turangi today, ranging from a magnitude 2.2 quake at 8.26am, to a 3.8 quake just after noon.
Mountain officials confirmed the swarm had been enough to set off Ruapehu's eruption detection system, which is designed to pick up seismic activity or any explosive blast that might trigger a lahar.
Once it is activated, it sounds sirens and sends out safety messages telling people to move to higher ground, while also firing out a radio tone across the Ruapehu Alpine Lifts' radio system.
Mt Ruapehu, Whakapapa & Tūroa Ski Areas told its Facebook followers that two things were needed to kick the system off.
"The first is earthquakes – we have a few happening over by Turangi today that are popping into the Ruapehu part of the system, the second are strong wind gusts that set off the airwave detectors," the company posted.
"For the alarm to sound, the system needs to see earthquakes and airwaves together – like the perfect storm mimicking an eruption.
"This morning we have had both factors and as a result, EDS alarms have sounded."
The company described them as "false positives" and said there was no cause for alarm.
"Thank you to those on the mountain for staying indoors and out of danger until you received the stand-down message. GNS, DoC and RAL are always watching the mountain, if anything changes – we'll make an announcement."
The company added that alarms from the system should always be treated as real.
"The public are urged to always follow instructions from the alarm system and from mountain staff."