Assuming there’s an inquiry into the damage caused by the February 22 Christchurch earthquake, it will no doubt want to consider why no warning appears to have been given, after September 4, of the likelihood of another big shake.
It’s not as if there were no precedents. The famous Napier earthquake of February 3 1931, which registered 7.8 on the Richter scale, was followed only 10 days later by another of 7.3 magnitude. And the 7.2 magnitude quake that struck Masterton on June 24 1942 was followed on August 2 by another that registered 7.0. In both cases, the second jolt was more severe in some localities than the first.
Despite this, I don’t recall any seismologist suggesting Christchurch should brace itself for a follow-up quake that could almost match the September 4 event for intensity. Certainly there were the usual warnings of aftershocks, but the advice was that these would taper off over time.
The February 22 quake caught Christchurch off-guard – but would the city have been so unprepared if people had been reminded of the Napier and Masterton double-whammies?