fftopic The 7.1 caused significant damage actually. Talk to the residents of Kaiapoi. It weakened buildings in Christchurch enough that the 6.2 finished them off. The G forces are only one part but it is the magnitude that is important because that is the intensity descriptor of the quake and it should always be read in conjuction with the quake depth. It is not the g force that damages so much but the duration of that force is applied. The 22/2 shake was a trampoline one, the first ever recorded I believe and that was the killer. I have papers and reports that have been generated from the quake sequence, plus geology texts in my book case. I did first year geology at uni as part of my degree, but the Seismology 101 practical I do not recommend.
When I did natural hazards work we always worked on the worst case scenario so made the assumptions that surface access to the disaster area would be severely restricted. Harking back to the Christchurch quakes we were lucky that HMNZS Canterbury was within the area and able to access the port. Lyttelton was cut off from the city by land. The major road and rail access routes to Christchurch cross major rivers both north,west and south. If bridges over those rivers had been severely damaged then we would have been cut off. That leaves the airport and if that had be severely damaged then what? Yes, you do work from history but you also have to take into account other scenarios and in NZ we are at a significant disadvantage compared to Japan because we have such a short recorded human history of earthquakes and tsunami here. Therefore how do we know who often these events occur and how many are large events? It was thought the the main divide fault rupture would produce around an 8 - 8.5 but now that is thrown into doubt because recent research suggests that the fault rupture length is actually significally longer, now being over 400km. The longer a rupture length the greater the magnitude of the quake, so now we are well into the great quake regime - possibly a 9.
At least wih quakes you can glean some history from the geologic record in NZ but paleotsunami research here is practically non existant. The first recorded tsunami in NZ is the 1855 Wairarapa event. Maori have records in various iwi oral histories of disasters that maybe tsunami and the causes are unknown. We can't accurately date the iwi records unfortunately. We had a 15m tsunami here in 1947 and it was disasterous - it destroyed a pub along the North Island East Coast. Again we don't know the cause or where it was generated but believe it to be locally generated. It was lucky that it happened there and not in Gisborne which was further along the coast.
So now do you undersand why I advocate for heaavy lift helo for NZDF. NZDFdoes need it for its own military capabilities but it is also required toundertake HADR and Chooks inthe HADR role are invaluable.