Canterbury quake risk falls

There is less chance Christchurch will be hit by another damging earthquake, but experts are warning residents that they are not out of the wood yet. Photo / Ross Becker.

The chances of another highly damaging earthquake in Canterbury have dropped to one in four, experts say, but they warn the worst thing people could do is to let their guard down.

GNS Science calculate the odds of another quake of in the range of magnitude 6 to 6.9 in Canterbury's "wider aftershock region" in the next year have dropped from about one in three, to about one in four, following a quieter period since June 13 - when a magnitude 6.3 quake caused widespread new damage.

It was also a magnitude 6.3 quake in Christchurch in February that left 181 dead. Christchurch city's risk of such a quake in the year ahead would be around 5 per cent.

However the odds of a magnitude 5 to 5.9 quake in the aftershock region in the next year remained very high, at 90 per cent or more, said GNS Science spokesman Dr Kelvin Berryman.

He said experts were "cautiously optimistic" that Canterbury had seen the last of the quakes in the magnitude 6 plus range.

"They are the ones that really do the damage. Fives certainly shake everyone up, and everyone knows about it, but increasingly they are not the ones causing so much damage," Dr Berryman said.

"Various...media commentary has been that we are done and dusted now, and let's just carry on - there's not going to be any more large ones. Well, we are saying that's not correct because it's a better chance than winning Lotto that there still could be a magnitude six plus (quake) running around."

It would be wrong for Cantabrians to "not continue to be prepared and to do all the standards things that Cantabrians are getting very good at".

"Be cautiously optimistic, but don't relax so much that you are not prepared anymore. We are only a month after June 13th, and we have got to remember that we went for several months post September (when a magnitude 7.1 quake struck) when things were settling down and going quite quiet and everybody was saying 'oh, we are done now' and the most devastating earthquake came along."

A quiet month was not enough "to be confident that we are done".

"Maybe six months, (we) might be starting to be more confident."