Brian,
part of the problem was that Christchurch was not in the area of what had been considered high seismic hazard. The main fault, the Alpine fault, is across the mountains to the west. The strike-slip part of that cuts across the northern part of South Island. So, if they were to decide to retrofit, they would not have done Christchurch, at least not first. The fault that had the M7 was not previously known.

But, I was "talking" about the pancake collapses of the taller couple of buildings, like the TV building. I don't know what the construction was or how many stories, but assume it was a relatively modern building of something like 10 stories. I'm not sure of this latter part.

Chris