The 1920 Garfagnana earthquake (also known as the Lunigiana earthquake) occurred on 7 September in Garfagnana and Lunigiana, both agricultural areas in the Italian Tuscany region. The quake hypocenter was located beneath Villa Collemandina. The maximum felt intensity was rated as X (Extreme) on the Mercalli intensity scale, and 6.6 on the Richter magnitude scale. It was one of the most destructive seismic events recorded in the Apenninic region in the twentieth century. Due to good news coverage, availability of official documents on the damage and abundance of recordings from surveillance stations throughout Europe, it was regarded as a first-rate case study to improve knowledge of tectonics and macroseismic analysis.
Geology
The epicenter of the 1920 earthquake lay within the inner zone of the Northern Apennines, which has been affected by extensional tectonics since the Late Miocene to Pliocene epochs. This extension is a result of the same process that opened the Tyrrhenian Sea during the same period, the rollback of the subducting Adriatic Plate. The continuing extension has resulted in a series of northwest-southeast trending normal faults bounding basins filled by the Pliocene to recent sediments. Near Garfagnana, there are two such basins, the Serchio and Magra grabens. The 1920 event is thought to have ruptured the east-dipping Casciana-Sillicano fault on the southwestern boundary of the Serchio graben. Lunigiana and Garfagnana are part of the Apennines, a mountain area located above a subduction zone between the Adriatic and Tyrrhenian tectonic plates. The region, crossed by different systems of active faults, is mainly mountainous and rocky, with noticeable variations in soil composition.
Earthquake
Foreshocks occurred on 6 September, including an intensity VI (Strong) event on 6 September at 2:05 p.m. Frightened by these foreshocks, many people choose to sleep outside their homes in the open air, since the weather was still mild in the late summer. The main shock came at 7:55 a.m. (local time) the following morning, after a few hours of calm, its epicenter directly under the town of Villa Collemandina.
The towns of Vigneta and Villa Collemandina were completely destroyed. Fivizzano, with its tall buildings in the city center, was almost totally demolished, those buildings that remained standing were later destroyed by the aftershocks. Piazza al Serchio and another 30 towns suffered substantial damage to buildings and infrastructure. Reports of collapsed buildings came from about 100 towns and over 350 comuni from eastern Liguria to western Versilia were affected. The earthquake was noticed by people in the French Riviera, Friuli, Marche and Umbria, over from the stricken area. Aftershocks lasted up until August 1921.
Damage
The earthquake wrought massive destruction. Near the epicenter, an area of about from Fivizzano in Lunigiana and the upper Garfagnana, received X (Extreme) damage, including the collapse of many buildings. Newspaper headlines read "Fivizzano is no more". A much bigger area, assessed at over , received significant damage, and minor damage was sustained by other regions in Toscana, Emilia Romagna and Liguria. Many provinces reported consequences from the shocks: nearby Lucca and Massa Carrara, Modena, Parma, Pisa, Pistoia, Reggio Emilia and La Spezia.
In Pontremoli the shock destroyed the rooftop of the Chiesa della Misericordia church: debris fell on the ancient organ, damaging it.
Roads near the epicenter were compromised, along with some bridges. Since rescue operations were mostly managed on a local scale (city or town, lacking any national coordinating authority), that was a minor detriment to relief work. More of a problem was the availability of first aid resources, which were scarce. There was also much less food and tents than what was needed.
In the broader damaged area, some springs changed their path or became cloudy due to a sharp increase in the content of Hydrogen sulfide.
On 21 September refugees were affected by an exceptionally violent downpour, further worsening their condition. The refugees asked Bishop Angelo Fiorini to intercede with the Pope, hopeful to receive some economic help or relief effort, but received only a blessing to the victims. On the other hand, many organizations of emigrants in the United States and Argentina managed to collect and send significant donations of money.