Posted by: egutoday | May 5, 2010

Science under Fire 3

Wednesday’s column (longer version)

A lot of us are working on understanding the sequence of big earthquakes happening on the Sunda megathrust west of Sumatra. This is an important problem and we are making good progress. The recent earthquakes have left a yawning gap under the Mentawai Islands; the megathrust hasn’t broken under the gap since 1797, it is strongly coupled there, it is now loaded more than it was when it last failed and interaction stresses from earthquakes in 2005, 2007 and 2009 have pushed it even harder. All of us are convinced that another big earthquake is imminent and the city of Padang (population 840000) sits on the Sumatran coast broadside on to the region of highest expected slip.

Do we agree on the detail of the science? Of course not. One of the few things we are certain about is that we don’t understand the process properly. So should we be talking to the Sumatran people about things we don’t fully understand? I strongly think that we should. There is an overriding consensus that a great earthquake and tsunami is possible; we all agree on that even though we don’t agree on the detail. On 30 September last year an earthquake M7.6 shook Padang demolishing whole areas of the city and killing 1200 people. This was not the earthquake we were waiting for but no one in Padang knew this at the time. People did not uniformly do what scientists would have liked them to. Many ran to the shore to see if the sea was receding before evacuating, others in their tens of thousands took to their cars and bikes clogging the roads and preventing escape on foot. But had there been a tsunami many people who evacuated as they had been told would have been saved and the death toll from the event would have been much smaller than it might have been. The 2009 Padang earthquake was a partial vindication for scientific intervention in social organisation though more work remains to be done.

Earthquake science is still a young game. We don’t know all the answers, we probably don’t even know all the questions but we do know enough to make a difference. Over the entire globe we can identify cities which are threatened by big earthquakes, we can’t say when they will happen and we can’t forecast their detail but we do know they are inevitable. This information will save lives if we can bring it forcefully to the right people. Medical science doesn’t understand breast cancer properly yet lives are saved every day by the application of incomplete knowledge. Earthquake science can do the same.

John McCloskey, School of Environmental Sciences, University of Ulster

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