Christchurch is currently the scene of a crisis. The GNS are trying to forcecast the next earthquakes and where. I would suggest that is optimistic. Geological processes on Earth have been acting for billions of years. Modern Man has been occupying this planet and recording these events for just 3000 years. Even then the quality of the seismic record is just 100 years old. They are forecasting in the dark. NZ has only been settled by Europeans for 200 years.
NZ's South Island lies on a strike-slip fault when extends right along the island. There will be ongoing releases of stress along that structure, which is not a single fault, but a system of parallel and sub-parallel structures, each with their own stress characteristics.
Earthquakes are of course brittle (shallow) or semi-ductile (deeper) releases of those cumulative stresses. The most exposed or vulnerable areas are those areas on deep sedimentary piles, because they will oscillate when the earthquake hits. Clearly a major stress release carries the prospect of ancillary stress, or may even facilitate ongoing primary stress release. There is no way of knowing given that the stresses would need to be measured under the sedimentary pile.
Many people are disillusioned with the uncertainty of living in Christchurch. The future of the city is in jeopardy. Life in NZ is already difficult with the recession and lack of business investment. It does not help that the only investment is replacing the capital investment destroyed. Other parts of the country will also feel the implications. The bad news is:
1. The loss of business as a result of the clean up and restoration of services
2. Loss of tourism as the prospect of more earthquakes remains
3. Loss of students who decide not to continue their education in NZ, and instead go to Australia, i.e. 23 Japanese students are currently still trapped in their school (I believe??)
4. Many of Christchurch's residents will leave the city. I suspect many of them will go to Australia for higher earnings, and to escape the threat. Australia seldom experiences earthquakes. Its a very large, stable continental craton. Having said that the Newcastle earthquake 15 years ago did a lot of damage. The threats there are around Camden (NSW) and Kalgoorlie (WA). So a small prospect of threat for such a large country, and the threat is subdued. NZ'ers leaving will have flow-on effects for the country. The destruction of come of Christchurch's oldest historic buildings is very sad.
The only good news is the hit to the NZD. NZ exports 95% of its commodity production, so this spells stronger capital inflows for the city. There has been thousands of after-shocks since the initial earthquake in Sept 2010. This one is not as strong as the last, but it struck the centre of the city. It has destabilised a lot of buildings.
The bad news is that the geological stresses released along the fault zone will create new stresses along the fault zone. The good news is that there are no other large cities on the Canterbury Plain....that is good news. You might not extent more bad news. I think this is as bad as it will get. After tremours will likely be in different areas, i.e. in the suburbs. The problem is the weakening of already weakened structures. So there will need to be a lot of demolition.
The other great risk for NZ is the threat of an earthquake in Wellington, which is far along the same fault system. Wellington is not as vulnerable though because its sedimentary pile is very shallow; or non-existent, since many people are living on bedrock (i.e. hill sides). The greater threat is earth slips in the case of Wellington, whereas in Christchurch it was the tremours and liquefaction of the unconsolidated, saturated sediments near the surface.