Seismic risk in Malta is considered to be low with little historic damage noted and no known victims. The archipelago is however in a potentially significant seismic zone and the risk to the population is probably undervalued.
Tectonics
The Maltese Archipelago rests on an underwater plateau, a relatively stable part of the African Plate. The islands are situated around 200 km to the south of the subduction fault between the African Plate and the Eurasian Plate. The pelagic plate forms a shallow platform separating the Ionian basin from the Western Mediterranean Basin, situated roughly under the Strait of Sicily. The plate is crossed by a rift zone formed of three grabens: the Pantelleria graben, that of Malta, and that of Linosa. These grabens are linked by a system of north–south orientation faults (sometimes west–east) with dextral cavities that are responsible for most of the earthquakes that can affect the archipelago. The islands themselves are made up of limestone rocks from the Oligocene and Miocene geological epochs, belonging to the Cenozoic era.
List of major earthquakes Prior to the 20th century and the first seismic recordings in the region, information on Maltese earthquakes was researched in archives. These range mostly from the arrival of the knights of the Order of St John of Jerusalem in 1530 to the British colonisation of Malta. After this period, the localisation of the epicentres of earthquakes in the Sicilian Channel has been relatively limited, mostly due to an inadequate network of seismic stations, particularly before 1980.
Summary table of earthquakes since 1500
Details of major earthquakes
Earthquake of 10 December 1542 The Sicilian Chronicle of the 16th century reports that the earthquake of 10 December 1542 was strongly felt in Malta where some houses were knocked down.
Earthquake of 11 January 1693
The earthquake of 11 January 1693 in Val di Noto is the most significant earthquake felt in Malta since the 16th century. In Sicily, it caused the death of around 60,000 individuals. With a magnitude of 7.4, it is considered to be the most powerful earthquakes in Italian history. The earthquake was preceded on 9 January by a precursory earthquake of a magnitude of around 5.9 which was strongly felt but did not cause damage. In Malta, the earthquake provoked panic among the population, with many Maltese refusing to go back to their homes in the nights that followed, seeking refuge in tents or underground shelters. No injuries or fatalities were reported. The Order delegated its head engineer, Mederico Blondel to assess the damage. At Valletta, no building escaped unharmed by the earthquake, from simple cracks to complete demolition. The other towns of the Grand Harbour were considerably less affected. However, the old city of Mdina suffered more greatly as many of the buildings were older and were poorly maintained. Notably, St. Paul's Cathedral was part destroyed – but the cathedral was already badly damaged before the earthquake, and so a reconstruction had already been planned. The Banca Giuratale in Mdina was equally damaged, and would be rebuilt in 1726 by Charles François de Mondion. At Rabat, the bell tower and the apse of the church of St. Paul came down. The Tal-Virtù Church suffered considerable damage, it was situated at a high altitude which was particularly susceptible to earthquakes.
At Gozo, the walls of the Cittadella were damaged, but Blondel notes that the damage were more likely caused by years of neglect. The Cathedral of the Assumption, Victoria lost its bell tower. The considerable material damage in Malta has been attributed to the maximum earthquake intensity of 7–8.
Earthquake of 20 February 1743
Local historian Gian Pietro Francesco Agius de Soldanis recounts 20 February 1743 earthquake in his magnum opus Il Gozo Antico-Moderno e Sacro-Profano, a two-volume manuscript dealing with the history of Gozo completed in 1746: ...At 5 pm, a violent earthquake shook the Maltese isles. It lasted for seven minutes. It left great damage on the two isles. At Gozo, the church of Saint George, Saint James and the chapel of Notre-Dame at Qala were greatly damaged. In Malta, the church of St John at Valletta, the cathedral of Mdina and many other churches were also effected. At Wardija, near Qala, people are said to have seen the earth rise and fall with such force that the soil seemed to remain floating in the air, creating a dust cloud that remained for a long time. Many of the hills in Gozo crumbled. A document in the archives of the cathedral of Mdina described how the coppolino (the little dome) of the cathedral fell into the church, the back end of the choir was destroyed and the bell tower heavily damaged. The cathedral was so cracked in all areas that: ...Even the sound of the bell didn't dare to enter for fear of seeing the building fall. An account by six architects described three large cracks of around 3 cm in width on each side of the cupola, revealing most of the stones in the cupola and the terrible damage to the walls of the choir.
Earthquake of 12 October 1856
The epicentre situated near Crete was very seriously hit by the particularly violent earthquake of 12 October 1856. Certain seismic registers attribute it with a magnitude of 8.2. It claimed numerous victims in Crete. Despite being at a distance of more than 1000 km from the epicentre, the earthquake was violently felt in Malta, as the newspapers of the era testify. People were woken in the middle of the night by a deafening growl and a movement of the earth that lasted between 22 and 60 seconds. Nearly all the houses in Valletta were damaged, as were houses in Gozo, notably on the upper floors. Numerous churches were affected, and in particular the cathedral of Mdina. The belltower of the church of the Carmelites at Mdina was so cracked that it needed to be rebuilt. The chapel on the islet of Filfla was destroyed. The 17th-century Għajn Ħadid Tower collapsed in this earthquake and has remained in ruins ever since.
Earthquake of 27 August 1886 This was probably the earthquake on the same day that struck the SW Peloponnese. Once again, the local papers reported a general panic in the population that rushed outside dwellings, awoken by the earthquake on 27 August 1886. Some buildings were affected, including the ceiling of the Palace of Justice in Valletta. For once, the cathedral in Mdina was not greatly affected.
Earthquake of 30 September 1911
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