'Ullo beardyboi...& welcome,
Actually, though Geology was my major in my first BSc, my chosen final subjects were Volcanology & Tectonics not Seismology, so I wouldn't be the best peson to listen to with regards to earthquake theory (though the Tectonics did pass over Seismotectonic Theory briefly), and I've never ever been a Geologist by trade - you generally need a Masters + 10 or so years in the field before you can truely call yourself "qualified" in the profession. So I'd hate to put you wrong with any mere opinion of mine. That said, I wouldn't know how to go about calculating seismic "risk" factors - I'm certainly no statistician - but there is a wealth of reputable information out there for New Zealand (one of the best - probably next to California and Japan - studied areas of the Earth, in an earthquake risk sense) and most of it makes good sense to me.
I would think that no place on Earth is actually temblor-free. And the next "big-one" could strike anywhere or perhaps rather I should say..."where-ever".... Everywhere on this planet is at risk. It's the nature of the place.
My assessment for NZ would be, that on the face of it, you are right, regarding the Sth E Sth Island.
The above "risk" map, based on temblor history & frequency (remember only 1-200 years worth) would appear to demonstrate such. However, I tend to take such things with a grain of salt. eg: it's now apparently pretty certain by new found stratigraphic evidence, that all of the present day Western N.I. harbours were formed very quickly at the same time, by block faulting during the Kaikoura Orogeny, rather than by a more gradual process as originally first thought. I also know that the geology of NZ is particularly bizarre ! And indeed has a host of geologic structures that can't be found (or havn't YET been found) all together in one place in the world... for instance - The Sth Island, a conundrum....in the Nth, the basaltic oceanic crust of the Pacific Plate is going under the basaltic of The Australasian Plate, in the centre both plates are just butting togeather (both continental crust) forming the Sth Alps, in the Sth the Australasian is going under the Pacific (both basaltic).....In the Top of The North Island we have another geologic conundrum, The Northland Chaos, (I think by memory it is actually called The Spoirli (sp?) Chaos - after the Swiss geologist that discoverd it) , layers of sedimentary rock in synclines and anticlines that go from young to old then to the young again then to the old again then to the young again then to the old again then to the young then to the old again....the strata (continuous) having been folded so much (and some with evidence of violence) that they have been flipped on top of themselves many times.... with various layers being metamorphosized in between - from igneous intrusions (and extrusions) of BOTH basaltic (oceanic crust) and andesitic (continental crust) lavas....The Central Nth I. has always fascinated me.....The Auckland and Taupo volcanic zones especially...where the andesitic, basaltic and rhyolitic all meet ! (pretty sure that there is nowhere else in the world that has such a trifecta in such a small piece of landscape).
Anywhoos, I divert.
The whole place (NZ) is very geologically active, even on "my" maunga (it's not "mine" K.K tho' "thanks"
it's Te Whanau's ),
there are soda fountains and warm silicate springs....so I doubt that it is inactive....merely dormant. I guess the crux of the matter is that Northland hasn't seen any earth shattering earth quaking experiances in living memory yet (tho' it could always happen), the tsunami risk here however is extremely high (and there is plenty evidence - both geologic and anthropologic - around , especially on the Nth-East Coast and the Aupouri Peninsula), that tsunami have certainly been no strangers to the region in the past :shock : ) - The Rumbles in The Kermadic's being just about the smoking gun ....
think what you want. you are wrong.
The church says the earth is flat, but I know that it is round, for I have seen the shadow on the moon, and I have more faith in a shadow than in the church.