"A detailed examination of the individual circumstances on the five green zoned properties suggests there are factors offering adequate protection," Mr Brownlee said.
The decision to zone 121 properties red is based on the on-going life risk threat but has also taken into account analysis of options surrounding mitigation, he said.
"Experts have looked at a number of mitigation options taking into account a wide range of factors, including timeframes for implementation, disruption to residents, and engineering and economic viability.
"It is not considered to be practicable to implement mitigation in these areas, and it should be remembered that nowhere in the world has mitigation for potential rock fall due to earthquakes ever been used.
"While I understand the desire for some people to stay in their homes, we cannot be confident that fences or bunds would offer adequate protection should the worst case scenario of another major earthquake occur."
Thirty-seven properties will remain zoned white - six in the Horotane Valley and 31 on Bridle Path Road.
Mitigation analysis has not been completed for these properties and a decision cannot be made until this is done, Mr Brownlee said.
"I'm sorry for those remaining property owners that we haven't yet brought the zoning process to a conclusion, but the delay simply shows the degree of rigour being applied to the work being done," he said.
Christchurch Mayor Bob Parker told Firstline that detailed geotechnical work still needed to be done on the remaining properties, but decisions "shouldn't be too far away".
Mr Parker said the land purchasing costs would be split 50/50 between the Government and the council.
He said the purchases will cost the council about $59 million, which takes into account the homes yet to be zoned. The council budgeted $55 million for the purchases, but Mr Parker said rates will not be affected.
