Wednesday, 21 November 2012

Communicating the risk of earthquakes

A recent article on the UoN "Making Science Public" blog discussed the issues of how scientists should communicate risk to the public - an issue that has been brought to the fore recently by the prosecution of six scientists (and a public official) in Italy for poorly communicating the risks of an earthquake in miscommunictaion of the risk of a major earthquake in L'Aquila.

Very helpfully, the article contains a link to the very comprehensive report on the issue by Nature.

It's perhaps worth outlining a few of the key points of the story:

1) In late 2008 and 2009, L'Aquila was hit by dozens of low-magnitude tremors (knows as seismic swarms), each month. Stronger shocks, around magnitude 5, occured on 30th March and 5th April.

2) L'Aquila is situated in an earthquake zone, and many of the inhabitants instincitvely leave buildings to spend the night outside when they feel tremors.

3) The concern at the time was whether these small quakes, and the 3.9 shock, were the precursor to something big.

4) Research suggests that the risk of a medium sized shock in a seismic swarm being accompanied by a major quake within 2 days to be around 2%. However, in a earthquake prone region such as the area around L'Aquila, there is always a certain level of risk of an earthquake.

5) A resident of the area, Giampaolo Guiliani, was using home made radon detectors to measure the levels of radon, which is alleged to rise significantly just before an earthquake (an idea that has not been scientifically proven). Guilianos predictions were causing public alarm.

6) Guido Bertolaso, head of Italy's Dept of Civil Protection, convened a risk commission on 31st March in L'Aquila. According to the minutes, one of the scientists said that "It is unlikely that an earthquake like the [severe] one in 1703 could occur in the short term, but the possibility cannot be totally excluded." But - and this is a key part of the prosecution - there was little discussion about risks of a severe quake to the old local buildings, or what residents should be advised to do in the event of a severe quake.

7) Shortly after the meeting, two commission members - Barberi(Head of Serious Risks Commission) and De Bernardinis(then vice-director of the Department of Civil Protection), along with town mayor Cialente and a civil-protection official department - held a press conference to discuss the findings of the commission meeting. According to the Nature article, "De Bernardinis said that the seismic situation in L'Aquila was "certainly normal" and posed "no danger", adding that "the scientific community continues to assure me that, to the contrary, it's a favourable situation because of the continuous discharge of energy"."

Importantly, there is no mention of the "Discharge" theory in the commission meeing notes, and a number of the scientists on the commission strongly disagreed with this statement.

8) The public comments - particularly that more tremors meant less danger - were reassuring for the local population and may have been a factor in some people staying at home after the 5th April shock.

9) At 3.32am on 6th April 2009, a severe magnitude 6.9 earthquake hit L'Aquila. It killed 309 people and destroyed some 20,000 buildings.

Further Comments
One interesting approach to commicating the risk of earthquakes is that taken by authorities in New Zealand who simply report the percentage risk of an earthquake and let the public make up their own mind as to what precautions they should take.

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