I have heard some people say that Christchurch is an earthquake prone zone with a magnitude of 4.0 always happening throughout the year. Is this true?
There was a devastating earthquake in 2011. Since then, Christchurch has undergone a transformative period in which more earthquake-conscious design and construction has been incorporated into the city.
The most severe, comparable earthquake before the 2011 Christchurch earthquake occurred in 1888, so these events seem to happen rarely, but in a big way.
So yeah, Christchurch is an earthquake-prone area, but earthquakes which cause significant damage are rare and the city, in general, seems to be getting better at dealing with earthquakes.
But don't quote me on this!
Otherwise, this Expat Arrivals page about moving to Christchurch provides an overview of the city.