A severe tropical cyclone, which may become a supercyclone, could be down-graded before it reaches NZ, but warnings are still being issued for residents to be prepared.

Northlanders are being urged to 'get ready' ahead of a national civil defence preparedness week in the wake of a series of storms which have battered the region this year.

Auckland has only 10 service stations wired up to provide fuel to emergency services quickly if electricity is cut in a natural disaster.

As they did on the afternoon of March 17, tens of thousands of Aucklanders take to Facebook and Twitter to express their amazement that their seemingly quake-free city has had a rumble.

An inter-agency plan was released today to strengthen the role of Civil Defence, so it can better respond to civil emergencies such as the Christchurch earthquake.

Christchurch mayor Bob Parker doesn't pull any punches in a personal account of the earthquakes that rocked his city.

Emergency services responded rapidly and worked well together during the February 22 earthquake in Christchurch last year, an independent review has concluded.

Locals have criticised the response to last night's Tongariro eruption as too slow but authorities have defended their procedures, saying they quickly established there was no immediate risk and put plans in place.

Rotoaira local David Bennett was concerned by the lack of communication between the authorities and National Park residents when Mt Tongariro erupted about 4km from his home last night.

The aviation colour code around Mt Tongariro has been downgraded from red to orange, but the volcanic alert level remains at 2.

News of Tongariro's eruption sparked a flurry of activity by Kiwis who have been awake into the early morning.