Now, I make fun of Arkansas, but I would never make fun of NZ! They are just 'special'.
And really, their seismologists have a government mandate to cheer everybody up. Thus, if you believe the M7.3 was a single-throw earthquake, instead of a complex of M6's, then everything after, is an aftershock. If you realize that this basin is so shattered it couldn't produce a clean M7, then you don't live in NZ.
With every earthquake, that circular basin is going down. In order to maintain the basin, against the forces of erosion, this is probably a common event, on the order of every 500 years or so. They say they didn't find any previous fault movement, but would they find any evidence for these earthquakes? The place is a soup, and it would be difficult to keep a trace of liquefaction for 500 years.
Since the soup is everywhere, they are going to have to build a new city on deep piles, or find some firm ground. These earthquakes are going to rumble for at least 10 years. A new city would be a great tourist attraction: "Come feel the daily earthquakes!" Every place would be designed like a ship, with ridges on the tables, and latches on all the cupboards. You could test out the really stupid engineering ideas, like soft-story condos, and base isolation. :)
ps. Dear NZ, I make fun of everybody. Don't get mad!