Insurance companies are preparing for an expected deluge of claims over the next few days with the damage bill expected to run into the billions.

The industry also assured customers that their policies would be honoured, even where payouts had occurred for damage caused by the September 4 quake and numerous aftershocks.

Risk modelling company Eqecat said the new quake would probably exceed $1 billion in damages, based on indications immediately after the event. However, determining losses from the new quake would be complicated by the damage left from the original September 4 quake, Eqecat said.

Insurance Council chief executive Chris Ryan said emergency response teams had been put in place to deal with claims when they began to flow in. But insurance firms were still in emergency recovery mode, with a number of staff still missing and severely damaged offices.

Staff were first being allowed to take care of their own families and homes, and only a small number claims had been received so far.

"It will probably turn into an insurance event by later this week or the weekend," Mr Ryan said.

A number of insurance companies had set up earthquake recovery teams in Auckland and Wellington.

Christchurch's AMI Insurance said damage to its premises meant all branches were temporarily closed in the city.

A British expert in engineering risk said insurance policies in many countries did not allow more than one claim for an "act of God" event a year. If damage caused by the aftershock was deemed to be part of the main quake in September then insurance would probably pay out, Imperial College London fellow Peter Stafford said.

But "if the quake is deemed to be independent then coverage may not be guaranteed", he said.

However, Mr Ryan said "archaic" interpretation of an act of God in Britain and part of Europe did not apply in New Zealand where the term was no longer used in policy documents. An assumption existed that an act of God was generally a term for an accident or unforeseen event. "It's what you take insurance for."

Discussions were under way among insurers whether the quake was considered a new event or part of the September quake.

- © Fairfax NZ News