6 April, 2009: L'Aquila Earthquake

At 3:32 in the morning a 20 seconds lasting earthquake with magnitude 6,9 (followed quite until midday by weaker aftershocks) occurred 7km near the city of Aquila, the capital of Abruzzo, within a depth of 8,8km.

Fig.1. Intensity map of Central Italy Earthquake 2009-04-06 (L'Aquila) from the USGS.

More than 45 towns were affected, 308 people killed, 1.600 injured and more then 65.000 inhabitants were forced to leave their houses.

Italy has a long and tragic history of earthquakes. The setting between to larger continental plates (the European and African) and various micro plates results in a highly active tectonics all over the peninsula.
The first map of seismicity of the Mediterranean area and an extensive research on earthquakes in Italy was published in 1857 by the Irish engineer - and self educated geologist - Robert Mallet under the title "Great Neapolitan Earthquake- The First Principles of Observational Seismology". Mallet got interested in earthquakes in 1830 by a drawing in a natural science book displaying two columns twisted by an earthquake in Calabria. He decided to study the forces able to do this to human constructions. In his work he noted that damages on constructions were distributed in distinct areas, setting out from a point of heaviest havoc. These points, the epicentre of an earthquake, were not randomly distributed, but found in "seismic belts" following the Apennines.

Earthquakes mark the history of the region surrounding L'Aquila and the province of Abruzzo, historic events or swarms of trembles are recorded from 1315, 1349, 1452, 1461, 1498, 1501, 1646, 1703, 1706, 1791, 1809, 1848 and 1887, one of the most important on the 2, February of 1703 which caused devastation across much of central Italy and largely destroyed the city of L'Aquila and killed 5.000 people.

The destruction caused by the earthquake of 2009 surprised experts and generated discussions about the antiseismic building standards adopted in Italy. While most of the medieval structures in rural areas collapsed or were heavily damaged, in L'Aquila most concern arouse the observation that the modern buildings suffered the greatest damage and that the death toll included mostly young people. L'Aquila was a university town and cheaper accommodations which suffered severe damage were inhabited by students, also many students died when a dormitory at the University of L'Aquila collapsed. Even some buildings that were believed to be "earthquake-proof" were damaged, like parts of the new hospital and various buildings of the government.
In rural areas the "core" of most of the historic houses consisted of local material, like stone, superimposed by cement constructions or supplementary storeys of modern age. It was this mismatch that caused the collapse of many buildings. In L'Aquila the earthquake of 1703 destroyed most of the ancient buildings, during reconstruction work first antiseismic regulations were introduced - the rebuild houses possessed thicker walls, improved joints between floors and the allowed height of the building was limited. Most "modern" buildings in contrast were build previously of 1984, before modern antiseismic buildings standards were introduced in Italy.
However there was and still is a widespread disregard of building standards and the ignorance by people and (in part corrupt) authorities of the seismic hazards. Many concrete elements of the collapsed buildings (like the hospital) "seemed to have been made poorly, possibly with sand" a common tactic to build fast and cheap by building enterprises controlled by criminal organisations.
The earthquake of L'Aquila was therefore only in part a natural disaster and the manmade catastrophe was strongly misused by Italian politics and economy and many promises are still unrealized today.

Fig.2. The local prefecture (a government office) damaged by the earthquake, emblem of the situation in Italy, from Wikipedia.



However most alarming were the legal repercussions of the earthquake on science. Based on a general lack of understanding of science by the public and authorities various persons were accused to have ignored "premonitory signs" of the earthquake and early warnings- pseudoscientific "premonitory signs" of dubious veracity and warnings mostly published by individuals in internet.

To cite what the geographer Grove Karl Gilbert (who studied intensively the earthquake in San Francisco of 1906) resumed during a meeting of the American Association of Geographers (AAG) in 1909 about the predictability of earthquakes:

"Common people would be satisfied to know if we reached the point where a scientific predictability for an imminent earthquake is possible."

But Gilbert criticised the simple belief that earthquakes automatically occur in cycles or after long periods of quiescence and that an extrapolation based only on historical records is possible.

"Considering the complexity of conditions and the chaotic interrelationships between underground tensions, it can not be assumed that the particular conditions of every epoch will repeat always at the same manner."

Gilbert concluded that we should not try to predict specific events, but to prepare for the general hazard:

"[seismologists should not]…try to enforce control on the course of nature, but with the support of science, predict the imminent changes, so to enable the people to be warned and to be prepared…[]. The determination of the instant of seismic hazard belongs to an indefinite future. It is still a realm of try and hope."

Bibliography:

TERTULLIANI, A. (2011): Il segni del terremoto sul tessuto urbano. DARWIN No. 42 Marzo/Aprile: 80-83
WALKER, B. (1982): Earthquake. Planet Earth. Time Life Books: 154