Earthquakes in and around Ferrara: an underestimated risk

Fri, 18 Mar 2011 14:45:46 +0000
Num. 33

The sismic sequence of 1570-1574: a significant event for the city's history

When we forget about destructive events of the past, such as earthquakes, we also lose the perception of the hazards to which we are exposed. Recent events in L'Aquila have provided a harsh reminder: the majority of the population were not aware that they lived in one of the areas of country with the highest risk of seismic activity. The "conscious memory" of the citizen can encourage an effective and responsible control over the quality of buildings. For several decades now an entire field of seismology, with the assistance of specialized historians, has been studying the earthquakes of the past. Why do we look to history at a time when natural sciences are accustomed to relying mainly on technology? The reasons are that analysis of historical data can provide the information necessary to locate epicentres, assess the propagation of earthquakes, evaluate the magnitude of the social and economic impact and supply statistics regarding the intensity of local seismic effects. On this basis it becomes possible to outline seismic scenarios of the future. In much of our country the cultural means required to transmit this type of knowledge to the population and to create a tradition of home security in a scientifically documented context, are absent. It is therefore important to know to what extent Ferrara and its surrounding territory are exposed to seismic risk? We are in possession of a great deal of data on natural disasters of the past, most of which had mild repercussions, but the earthquake that began in November 1570 played a crucial part in the history of the city: not only as a social, cultural and political event, but it also provides vital information for current risk assessment with regard to residents, houses and monuments. Between November 1570 and the end of 1574 Ferrara was at the centre of a long and powerful seismic sequence, with over two thousand tremors. Approximately 40% of homes were damaged, as well as almost all major public buildings. Many churches suffered partial structural collapse. It was a disaster that the city never really recovered from, apart from the material damage it also induced a general sense of confusion in the population, mistrust in human endeavour and in the destiny of the city itself. The earthquake was interpreted by some as an act of God against the city, and by others as an event that questioned established theories, making the "philosophers of nature" (the scientists of that time) contemplate on the causes of earthquakes. This sense of insecurity and perception of divine punishment that the inhabitants experienced, was accompanied by a suspension of all established rules regarding cohabitation. The population was forced to seek refuge in makeshift shelters, where people from all social levels found themselves living side by side for months at a time, in a state of promiscuity that even involved the ruling family and their entourage. The image of the Duke's Court transferred to provisional tents profoundly impressed the imagination of the people, creating an extraordinary amount and variety of sources of information: diaries and eyewitness accounts, several treaties aimed at investigating the causes of the event, even sonnets and poetry were composed. These events all took place when the political stability of the city was going through a particularly sensitive phase. If the Duke died without heirs, the Duchy of Ferrara would be donated to the Holy See and, with this in mind, various Popes had persistently tried to undermine the strong local support for the dynasty in an attempt to delegitimize the Dukes. So the significant seismic sequence that began in November 1570 became a sort of diplomatic weapon used by Pope Pius V to weaken the prestige of the House of Este. Hence the efforts of Alfonso II d'Este to distance himself from even the slightest suggestion of sin, presenting himself as a good Catholic and seeking by every means to minimize the damage caused by the earthquake to the eyes of the world. In 1571 at least six treaties were written about the earthquake in Ferrara, including Libro, o Trattato de' diversi terremoti by Pirro Ligorio (renowned architect and learned scholar in the service of the Este dynasty since 1550). In his Libro Ligorio, who claimed to be a fervent Catholic, made use of history to suggest that earthquakes had always happened, adding an accurate daily account of the frequency of the tremors. According to Ligorio the main cause of damage was the poor quality of the buildings in Ferrara, built with shoddy materials and following extremely approximate, if not totally incorrect, construction techniques. In the final part of the book, entitled Rimedi contra terremoti per la sicurezza degli edifici, Ligorio presented an anti-earthquake construction plan that was unprecedented in Western culture, based on a concept that astounds because of its modern approach. It is remarkable that this project was born in Ferrara, and today the city can reconsider its seismic condition from an almost privileged position. The trauma of the 1570 earthquake brought worries, doubts and uncertainties to the minds of the people of that era. It became an instrument of the Pope's aggressive strategy, and by emphasising the alleged culpability of the Duke (in particular with regard to his protection of Jews and converts), Pius managed to weaken the relationship of loyalty that bound Ferrara's subjects to the House of Este. But this period also produced the rimedi to protect us against the hazards of future earthquakes. Ligorio called this quest a "duty of the human intellect". This faith in rationality must be looked at positively and can now be considered as a precious legacy of those times.