This post was contributed by Bryony Stewart-Seume, of Birkbeck’s Department of Biological Sciences.
Professor Gerald Roberts. Photo: Harish Patel
Science Week continued with a popular lecture about the widespread damage and complicated scientific questions arising from earthquakes.
Professor Gerald Roberts, of Birkbeck’s Department of Earth and Planetary Sciences, delivered a talk, entitled Earthquakes in Italy: the role of the historical record of earthquakes and geology, on 18 April. He began with a little history. The 1915 Avezzano earthquake killed a reported 30,000 people, and destroyed all but one building.
On 6 April 2009 an earthquake with its epicentre close to the town of L’Aquila in central Italy killed “only” 309 people. However, 30-50 per cent of the buildings in the town were badly damaged or razed to the ground, including a halls of residence in which eight students lost their lives. To better get an idea of the extent of the damage to the town (the centre of which has still not been repopulated), Prof. Roberts asked us to imagine half of the city of Bath being damaged beyond repair.
In an unfortunate twist the Town Hall of L’Aquila, which contained plans for dealing with such situations, was also badly damaged. Several 13-15th century cathedrals and churches were damaged and part of the modern hospital fell into the underground car park below it. The older masonry buildings proved especially vulnerable.
The financial cost of the 2009 earthquake has been estimated at €16 billion .
Scientists in the dock
There is, however, more to the story of the L’Aquila earthquake of 2009 than damage and a number of deaths. Prior to the earthquake citizens concerned by a number of tremors that had been rocking the city called upon the National Commission for the Forecast and Prevention of Major Risks to give an idea of the potential danger. What followed was unfortunate, in that initially the answer was along the lines of “it is not possible to predict earthquakes but this area has a long history of earthquakes and you should be vigilant”; a correct statement, but subsequently one of the members said in a TV broadcast that there was “no danger” which was not correct.
When the earthquake did hit, police had reportedly told people that as there was “no danger” they should return to their houses. Seven members of the National Commission were subsequently tried, and convicted, for involuntary manslaughter. Their conviction was met with disgust by parts of the scientific community, although it was stated by the judge that it was not science that was judged, or the inability to predict an earthquake, but the failure to communicate consistently. This highly controversial conviction has led to concern amongst scientists about the future for those studying and communicating earthquake science.
So what can be done about this? Earthquakes will not stop happening. The African plate will not stop pushing into the plate containing Italy. And Italy will not stop being pulled apart. So how can we better communicate what we do know, and what we can do?
Asking the right questions
The question “when will there be an earthquake here?” is not one that can be answered. When an earthquake happens along any given fault is unpredictable. That an earthquake will happen along any given fault is inevitable. Earthquakes are caused by the movement of the plates of the Earth’s crust. Professor Roberts demonstrated through use of a model with springs and metal blocks moving on a sandpaper surface just how chaotic the movement is. The elastic crust pulls apart (or pushes together), tension builds up and the ‘elastic’ releases. This is what causes the earthquake itself.
Professor Roberts took us through a more useful series of questions that populations should be educated to ask rather than the standard “when” question, the first being; does my area have a history of earthquakes. If you happen to live in central Italy the answer is obviously and demonstrably “yes”.
The next question that should be asked is; do I live in an earthquake zone? If you live near to an active fault, the short answer is “yes, you do.” But how active is it? How can that be measured? The question to ask here is “how much has the fault shifted, and how quickly?” This is measurable, believe it or not, with the help of supernovae – burnt out and blown up stars that send out high energy particles that react when they hit calcium, for example in limestone around L’Aquila to produce new 36Cl atoms.
Professor Roberts stressed that although earthquakes cannot be predicted, in areas containing active faults they are inevitable and this needs to be communicated to populations.
The more time that elapses between each earthquake the more tension builds up and therefore the bigger the quake will be when it does happen. Which it will. They are inevitable, but not predictable.
Given that it is the building that kills you, not the earthquake itself, the best way to prepare for a quake is to make sure your buildings will take the strain. Buildings made out of cubes are weak and no match for the ferocity of nature. But if you reinforce the buildings with struts to make triangles in corners, you will improve the integrity straight away.
There is, therefore, a need to educate populations about the right questions to ask and about the significance of small tremors. These questions should be asked many years in advance to ascertain whether earthquakes are inevitable in the area they inhabit and how they can undertake actions to prepare buildings to withstand the seismic shaking.
Just because there has not been an earthquake for a long time does not mean that you are safe. In fact, quite the opposite. All this needs to be conveyed, but without being alarmist.
