about the L'Aquila trial
From: Warner Marzocchi <warner.marzocchi@xxxxxxx>
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I would like to share with the volcanological community my thoughts about the recent L'Aquila trial.
(an edited version of these thoughts will appear in the December issue of Physics World)
On April 6, 2009, a Mw 6.2 earthquake struck beneath the city of L'Aquila, Central Italy. The shock created significant damage in the city and caused more than 300 deaths in the city and environs. The event followed a seismic sequence that started at the beginning of the year, with its largest shock of Mw 4.2 occurring on March 30. On March 31, the Grandi Rischi Commission (CGR), composed of scientists and emergency managers, met in L’Aquila and released a brief report pointing out: 1) earthquakes are not predictable in a deterministic sense; 2) the L'Aquila region has the highest seismic hazard in Italy; 3) the occurrence of a large earthquake in the short-term is unlikely. These statements were interpreted by the community as a reassuring message. The need for such a message, and indeed for the meeting of the CGR, arose from the release of contradictory information from a local Civil Protection official and from the anxiety of the population generated by some earthquake pre
dictions issued by Giampaolo Giuliani, a technician at the National Institute of Nuclear Physics, using his own personal method based on radon measurements. It is common knowledge amongst professional seismologists that radon is not a reliable earthquake precursor, and none of these predictions were proved to be correct.
After the earthquake, seven scientists and emergency managers who participated in the meeting were accused by the L'Aquila prosecutor of not having advised people to abandon their houses. This statement was interpreted by some Italian seismologists as an accusation of not having predicted the earthquake. They wrote an open letter signed by thousands of scientists worldwide denying this claim. The official indictment was released afterwards and did not contain such a bold statement about earthquake prediction, but it did charge them with manslaughter, asserting that scientists provided an inadequate risk assessment that led to scientifically incorrect messages being given to the public. The trial ended in October 2012 with the judge convicting the accused scientists and emergency managers, and sentencing them to prison terms of 6 years.
This draconian sentence has raised widespread concern, and shocked the scientific community. Undoubtedly, this trial and the verdict represent an extremely worrisome precedent that must be considered by scientists when offering their services in the interests of public safety. The whole situation is still rather hazy. Newspapers reported partial descriptions, often without specifying the context and the chronological order of the facts.
After careful reflection, both the accusation and verdict leave me very confused. Prosecutors repeatedly claimed that it was not a matter of science. Yet, several scientists were called to challenge the CGR statements. Some of them, in opposition to what is generally believed by seismologists, disputed the validity of Probabilistic Seismic Hazard Assessment, which is a standard procedure in many countries to define the building code and had been used to identify the L’Aquila region as one at risk. Another scientist alleged that the seismic sequence could be a clear sign of an impending large earthquake, even though the majority of the seismological community agrees on the fact that it is not yet possible to identify a priori a seismic sequence that anticipates a large shock with respect to the many other seismic sequences that do not end with a big earthquake. In addition, the prosecutor, judge and lawyers discussed in the court the results and reliability of different earth
quake occurrence models. Their naive, if not totally incorrect, interpretation of scientific results would have bewildered any scientist.
Along the same lines, the prosecutor talked about "negligence" and "underestimated risk", implying that he actually knew what the real risk was and what was the best practice to adopt in these circumstances. The accusation implicitly follows this logical fallacy: "if scientists say that an event is unlikely, but this event actually happens, this means that the scientists are wrong".
This accusation has other menacing aspects. At the beginning of the eighteenth century, the Swiss pioneer of probability theory, Jacob Bernoulli, wrote: "Do not judge human action by what happens". By definition, taking a decision under uncertainty means that you cannot always take the decision that you would have chosen after the event. If this basic concept is not accepted, scientists, decision makers, and indeed anybody involved in public safety, may always be prosecuted after the occurrence of an unlikely event.
So, was a mistake made at the March 31 CGR meeting? This is a very tricky question, and we have to put the situation into context. During a minor seismic sequence, the daily probability of a damaging event increases, but it remains almost always much below 1% (an unlikely event). Before March 31, 2009 (and even today), in Italy and in many other countries, there were no protocols for providing scientifically based advice and for communicating the risk to the affected population. It was also an issue that rarely receives attention in the seismological community. Therefore it is not surprising that the meeting was brief and the conclusions apparently trivial (even though substantially correct) and largely foreseeable in advance. Seismologists and decision makers learned a great deal from the L'Aquila event, but I think it is unfair to use what we have learned after the event to accuse people about what happened before. We have to be aware that this will happen again in the fut
ure. The next disaster likely will teach us something new. Can it be right to use what we will learn then to accuse scientists for what they know now?
An International Commission formed after the L'Aquila earthquake led by Thomas Jordan, director of the Southern California Earthquake Center, summarized the lessons learned (https://dl.dropbox.com/u/51584618/AG_jordan_etal_11.pdf
).
Beyond underlining once more that our best defense against earthquakes
is to build according to a sound seismic building code, the
International Commission emphasizes the need to establish transparent
and objective decision making protocols to manage the seismic hazard in
the short term, and the vital importance of effective communication. The
trial dramatically slows down any progress in this direction. Now,
scientists are afraid and will want to have legal protection before
making any kind of public statements. For this reason, the new president
of CGR, Professor Maiani, and many members of the commission, resigned
immediately after the verdict.
Hopefully, this impasse will be overcome, and efforts to inform the public about earthquake hazards and actions that can reduce the risk may be resumed. Citizens and decision makers need to be educated about the kind of scientific information that scientists can provide, its relative uncertainty, and its limitations. In particular, it should be recognized by all that unlikely events may always occur, in seismology as in many other hazard sciences like volcanology.
Warner Marzocchi
Hopefully, this impasse will be overcome, and efforts to inform the public about earthquake hazards and actions that can reduce the risk may be resumed. Citizens and decision makers need to be educated about the kind of scientific information that scientists can provide, its relative uncertainty, and its limitations. In particular, it should be recognized by all that unlikely events may always occur, in seismology as in many other hazard sciences like volcanology.
Warner Marzocchi
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