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Christchurch earthquakes demonstrates people were caught by surprise

February 26, 2015

Christchurch earthquakes demonstrate that people generally do not take any notice of the likely occurrence of rare events, University of Canterbury natural hazards researcher Professor Tim Davies says.

The February 2011 earthquake was a one in a many thousands of years’ event and there were many more important things to worry about prior to the September 4 2010 earthquake, he says.

Professor Davies is attending and speaking at the United Nations world conference on disaster risk reduction in Sendai, Japan, from March 14 to 18.


The conference hopes to produce countermeasures to climate-related disasters, which are worsening in some parts of the world. Japanese organisers will draw on its experiences of the March 2011 quake and tsunami and help stress the importance of preparation.

“Before the Christchurch earthquakes, large in our minds was an Alpine fault earthquake. We started preparing for that potential event in the 1990s and 2000s, because it had a much greater probability of occurring than anything else we knew about. The lesson here is that probabilities do not tell us everything future about disaster events – especially the ones we don’t have much information about.

“The most important disaster for any community is the next one, and probabilities can tell us nothing about that. We cannot know far in advance its type, its intensity or its time of occurrence. What any community needs to know is what the next disaster can do, and prepare by altering its behaviour so that when any disaster happens, the effects will be reduced.

“A community could, for example, anticipate that any disaster can cut off its food supply, and maintain emergency stocks; it can arrange that all the major professionals such as doctors, police and fire crew do not work in the same building, so that all don’t get wiped out by the same event.

“It can purchase and maintain satellite phones, anticipating that a range of events can knock out mobile and landline communication. None of these requires that the nature and probability of the next disaster are known.

“It is legitimate to use methods to devise risk-based strategies for dealing with the cumulative effects of large numbers of disasters, because the statistics will in that case be close to what actually occurs. However, such large scale strategies cannot be effective at reducing local disasters, because these are all different. If local disasters aren’t reduced, no large-scale disaster reduction strategy can be effective.

“Communities need to develop, in collaboration with scientists and officials, their own views on what the next disaster can do to them, and how they can become less vulnerable to it. The community itself knows how it functions; scientists can tell them how nature behaves; and officials can if necessary alter rules to allow resilience to be improved.

“There is much we do not know about natural hazards, and disasters will always be to some extent unexpected. Therefore risk management methodologies will always need to be supplemented with resilience methodologies if we are ever going to be able to reduce the impacts of future disasters – bearing in mind that rapid increases in population, development and commerce render society ever more vulnerable to nature’s challenges,” Professor Davies says.