This year marks the centenary of the Garfagnana and Lunigiana earthquake, the seismic event which from the historical catalog appears to be the strongest known to date for the northern Apennines. It is important and necessary to remember this in order to maintain high attention on the issue of seismic prevention understood both as structural prevention (interventions on buildings to make them safer from the impact of earthquakes) and as risk education for populations living in seismic areas. To find out about the events of 7 September 1920 and the days that preceded it, we interviewed Filippo Bernardini, a geologist at the INGV headquarters in Bologna.
The second half of the XNUMXs was a complicated period for the Italian state, which was still relatively young at the time. What happened in those years?
It is a very difficult period for all of Europe. Those were the years of the First World War, a very heavy war to which was added a tremendous Spanish flu pandemic which claimed about 600.000 victims in our country alone. The populations were in precarious conditions and poverty, and were exhausted. As if all this were not already dramatic enough, earthquakes also followed in Italy at that time, starting with the catastrophic one which struck Abruzzo in January 1915 with its epicenter in Marsica, causing over 32.000 victims, of which about 10.000 in Avezzano alone completely razed to the ground. In the following years, from 1916 to 1920, an impressive series of strong seismic events affected the northern Apennines, repeatedly hitting an area extending from Umbria to Liguria, passing through Tuscany, Emilia-Romagna and the Marches. In 1916, in May and August, two earthquakes of magnitude 5.8 occurred in the Rimini area. In April 1917 it was the turn of the Alta Valtiberina, hit by a seismic event of magnitude 6. Things went no better the following year with a magnitude 6 earthquake in the Forlì Apennines, nor in 1919 when on 29 June a strong event of magnitude 6.3 had very serious effects in Mugello. Since these are often neighboring places, the damage suffered by some towns was repeated. It wasn't over: in September 1920 what is considered the strongest event occurred not only in that series of tremors but also in the history of the entire northern Apennines.
What were the characteristics of the September 1920 sequence?
The sequence of September 1920 hit two adjacent areas located in the extreme north-west of Tuscany: the Garfagnana, an area of the province of Lucca corresponding to the upper valley of the Serchio river between the Apuan Alps, to the west, and the northern Apennines, East; the Lunigiana, corresponding to the hydrographic basin area of the Magra river, mostly in Tuscany (province of Massa-Carrara) and to a lesser extent in Liguria (province of La Spezia). These areas were well known in the Italian seismological tradition for their seismicity, so much so that Mario Baratta already in 1901 (therefore 19 years before the 1920 earthquake) had defined them as a "well identified seismic region with several active centres". The sequence began on 6 September with some minor tremors. Particularly strong was the one felt at 16.05 local time, with a magnitude probably greater than 5, felt in Versilia, Pisa, Florence, and as far as Genoa and Milan. There was already some minor damage and many people, alarmed, slept outside their homes that night, also thanks to the mild climate of the period. This was providential because the next morning, at 7:55 local time, a very strong earthquake measuring 6.5 struck the area, killing 171 people and wounding another 650, as well as several thousand displaced people. The event was so powerful that it was recorded by all Italian and European observers of the time. The destructive effects extended from the area of Fivizzano (MS), in Lunigiana, to the area of Villa Collemandina (LU), in Alta Garfagnana, where they reached or exceeded grade IX on the Mercalli-Cancani-Sieberg - MCS scale. In some small mountain villages the maximum effects reached grade X on the Mercalli-Cancani-Sieberg (MCS) scale and the villages were almost completely razed to the ground.
We have received many testimonies of this earthquake, why did the event arouse so much interest?
Firstly because it is a relatively recent event, just a century ago, and we have received many historical sources that speak of it and photographs that depict its effects. For example, the main national newspapers, such as Corriere della Sera, La Stampa and Tuscan newspapers such as La Nazione or Telegrafo, already existed then and accurately described the events of those tragic days. Secondly, that period was characterized by a great scientific interest in natural phenomena, which had already been going on for decades. During the 7th century, the first geological, seismological and environmental societies had arisen aimed at studying natural events. After the earthquake of 1920 September 7, many scholars went to the disaster sites to document both the effects on the natural environment, such as the fractures in the soil and the numerous landslides, and the damage to the inhabited areas. A precious testimony comes to us from a geologist from Garfagnana, Carlo De Stefani, who lived in Pieve Fosciana and was there in those days. De Stefani describes in detail how he perceives the shock of September XNUMX, the directions of the movement, the undulations:
"A first phase in terms of intensity of the previous rumble and in terms of length and energy of the following wave vibrations was completely identical to that of the previous afternoon [the earthquake of 16:05 on 6 September, ed]. After a brief rumble it seemed to me that the undulations proceeded between E and O or vice versa, but suddenly an instantaneous jerking impulse followed as if by explosion […] less than a second followed, the collapse of the chimneys, roof terraces, buildings with the noise relative. The impulse was followed by an undulating movement of 10 to 16” longer and more intense than the first period, which retouched, so to speak, the ruins that had already occurred…”
From his words it can be assumed that the shock lasted a few tens of seconds. These precious testimonies allow us to reconstruct the picture of the effects quite faithfully.
How far did the medium and minor damage go?
In addition to the destruction in Garfagnana and Lunigiana, the quake caused medium and light damage in a very large area, extending to the eastern Ligurian Riviera as far as Genoa, Versilia, the mountainous areas of Parma, Modena, Pistoia and the province of Pisa. There were numerous cities where "minor" damage was reported, such as injuries to various buildings, the fall of chimney pots and cornices: Pisa, Lucca, Livorno, Viareggio, Massa, Carrara, Pistoia, Genoa, La Spezia, Parma, Modena. This is a remarkably large area, as we would expect to happen with a magnitude 6.5 earthquake.
How were the rescue operations?
The area of Garfagnana and Lunigiana, morphologically mountainous, underwent collapses and landslides which interrupted the road system, which at the time was more precarious than today. The earthquake had also rendered the telegraph lines unusable. All of this caused a delay in the rescue efforts of hours and in some cases even days. Despite all the number of victims, 171, it could have been much higher: what saved many people who had slept at home was the hour
ary. At 7:55 many had already left to work in the fields and farms, mostly elderly people and children remained in the houses. And then, as we have already said, the earthquake of the previous afternoon had driven many to sleep outdoors.
How long did the reruns of the seismic event last?
The numerous reruns lasted for years. Which shouldn't be surprising, because for a magnitude 6.5 earthquake we can expect a sequence of a few years, as happened with the one in 2016 which is not yet completely exhausted. In that case the maximum magnitude (for the Norcia event of 30 October 2016) was similar to that of the 1920 earthquake.
The earthquake caused a lot of damage to buildings. What type of building characterized the places of the epicenter?
In Apennine earthquakes, the areas affected are often poor and rural areas where local construction is mainly made up of construction materials that are easily available locally. These often consist of stones, mainly rounded and smooth river pebbles, which therefore do not fit well together, held together by often poor quality material. As a result, the walls are fragile and this favors the severity of damage in the event of an earthquake.
Today there is a lot of attention on the subject of the vulnerability of buildings. The areas of Garfagnana and Lunigiana have become veritable laboratories where prevention work has been underway for some decades now through regional laws and anti-seismic adaptation interventions. The results were appreciated in June 2013, when a magnitude 5.3 earthquake struck the area between Fivizzano (MS) and Minucciano (LU), causing very limited damage compared to what we could have expected. This is definitely the way to go.
In your family you have had a precious testimony, that of your grandmother and her sister. What did they say about the earthquake?
Yes, it is a testimony that has impressed me since I was a child.
My grandmother, born in 1904, was in Versilia, in the Marina di Pietrasanta area that September, to spend the summer in a farmhouse with her family and other relatives and friends. She was sixteen at the time and what happened to her affected her so much that she told it all her life. That morning of September 7, the earthquake surprised her and her sister in bed, it was almost eight in the morning. They were on the upper floor and in an attempt to escape they were unable to walk the stairs because the steps "ran away" under their feet and the handrail "ran away" from their grip. They were terrified by the force of the event, it was not possible to stand. In the following days, on the beach and in the garden, they often felt vibrations from the ground: they were the aftershocks of the earthquake.
Are there any events planned to mark the centenary of this earthquake?
Yes, the centenary of the 20 earthquake is very important because, as we have said, it is the historically and seismologically strongest earthquake known to date for the northern Apennines. It is necessary to remember this in order to keep the focus on the topic of prevention high. In this regard, a project of meetings with the schools of Lunigiana and Garfagnana will be launched this year aimed at teachers and children to raise awareness of seismic risk and understand how to contain it.
Furthermore, on the occasion of the 2020 edition of "Io non Rischio", the campaign promoted by the Civil Protection Department in collaboration with INGV and other partners, information gazebos are planned in the squares of Fivizzano and Castelnuovo di Garfagnana to raise awareness population and inform them about the earthquake risk, obviously in conditions of safety due to the current health emergency.
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