I was alerted to the Christchurch earthquake this morning by comments in OpenMike. Since then I’ve been sating myself on NatRad’s excellent coverage.
But after determining the extent of the damage, I started looking at the Hawkes bay earthquake in 1931 which was the last one that hit a urban centre. From wikipedia..
The 1931 Hawke’s Bay earthquake, also known as the Napier earthquake, occurred in New Zealand at 10:47 am on Tuesday February 3, 1931, killing 256 and devastating the Hawke’s Bay region. Centred 15 km north of Napier, it lasted for two and a half minutes and measured about 7.8 on the Richter scale (7.9 on the moment magnitude scale). There were 525 aftershocks recorded in the following two weeks. The main shock could be felt in much of the lower half of the North Island.
Nearly all buildings in the central areas of Napier and Hastings were levelled (The Dominion noted that “Napier as a town has been wiped off the map”) and the death toll included 161 people in Napier, 93 in Hastings, and two in Wairoa. Thousands more were injured, with over 400 hospitalised. The local landscape changed dramatically, with the coastal areas around Napier being lifted by around two metres. Some 40 km² of sea-bed became dry land, where the airport, housing and industrial property developments now exist.
Within minutes fires broke out in chemist shops in Hastings Street. The fire brigade almost had the first fire under control when the second broke out in a shop at the back of the Masonic Hotel. The hotel was quickly engulfed in flames. The wind at this point also picked up strength and began blowing from the east, pushing the fires back over the city. With water mains broken the brigade was unable to save many buildings. Pumping water from Clive Square they were able to stop the fires spreading South. Only a few buildings in the central Napier area survived. Some withstood the earthquake only to be gutted by fire. Trapped people had to be left to burn as people were unable to free them in time. By Wednesday morning the main fires were out but the ruins still smouldered for several days.
While the damage in Christchurch is significant, it pales in comparison to what would have happened if we were still on the building codes of the 1930’s. Christchurch will be receiving aftershocks for days or weeks, and repairing itself for many months. However it appears that the structure of the city has no significant damage.
The hordes of engineers and government agencies that will descend on the city will be looking particularly at what buildings and structures suffered damage and how (especially the more modern ones) to adjust our building codes. However it appears that the work done in the last 80 years has largely done its job.
If you look at the list of major earthquakes in NZ, and click through some of the links of the effects of previous earthquakes when we had lower populations, the problems could have been far far worse.
This is probably of small comfort to the residents of Christchurch at present surveying the damage, creating ad-hoc toilets, and conserving water. However without the regulatory work done over the last century in steadily upgrading buildings and infrastructure to cope with shallow earthquakes, we would be looking at a major disaster in one happening so close to a major population centre. Kudos to that sustained effort, usually in the face of considerable opposition from developers.
As Christchurch rides through the aftershocks and cleans up, what will be interesting to see is how well the insurance and EQC systems stand up to the costs of repairs.