The Royal Commission into the Canterbury earthquakes has been told 300 more people could have been killed in the February earthquake.
The scenario could have occured if buildings hadn't been demolished or cordoned off due to the quake five months earlier, an expert says.
The commission has been hearing evidence about the performance of un-reinforced masonry buildings in the February earthquake in Christchurch, in which 182 people died.
Associate Professor Jason Ingham of Auckland University says he was asked to calculate the likely death toll if the September earthquake had not occurred.
"Obviously these numbers are open to great debate but they have been shared with my co-authors and we felt that they are sensible," he said.
He says many un-reinforced masonry buildings that suffered some damage in September would have been extensively damaged in the February quake.
Prof Ingham says taking into account the number of people who otherwise would have been in and around those buildings, he believes an additional 300 people would have been killed.
As as example he said the multi-storey Manchester Courts would have completely collapsed in the February earthquake, even without the damage suffered in September.
The demolition of this building was the subject of vocal opposition by heritage advocates following the September earthquake.
And he said that New Zealand has known for 150 years that unreinforced masonry buildings collapse in major earthquakes, and they will continue to do so if not strengthened.
