1857 Basilicata earthquake
Damage to the village of Pertosa, a photograph by Alphonse Bernoud
Epicentre of earthquake
|Date||December 16, 1857|
|Magnitude||Estimated 7.0 Mw|
|Countries or regions||Kingdom of the Two Sicilies|
|Casualties||11,000 – 12,000 dead|
The Great Neapolitan Earthquake was an earthquake that occurred on December 16, 1857, in the Basilicata region of Italy southeast of the city of Naples. The epicentre was in Montemurro, on the western border of the modern province of Potenza. Several towns were destroyed, and estimated fatalities were around 11,000 – 12,000, but unofficial sources report 19000 deaths. At the time it was the third largest known earthquake, and has been estimated to have been of magnitude 7.0 on the moment magnitude scale.
The principal shock occurred at about 10pm on December 16, 1857, and had been preceded by minor disturbances and was followed by numerous aftershocks which continued for some months.
The earthquake was felt as far away as Terracina to the northwest, the main places suffering damage being Potenza, Polla, Diano, Sala, and Padula in the Val di Diano, and Tito, Sarconi, Marsico Nuovo, Saponara, and Montemurro. The latter two places, along with Padula and Polla, were virtually completely destroyed.
Scientific study 
Early in 1858, aided by a grant from the Royal Society, Robert Mallet visited the devastated area, and spent over two months studying the effects of the disaster, paying special attention to the damage caused to buildings. His extensive report was published in 1862, and remains a memorable work in the history of seismology. It is believed that Mallet was the first to use photography to record the aftermath of an earthquake. 
Much of Mallet's work was devoted to determining the position and magnitude of the subterranean focus of the earthquake. He calculated that the focal cavity was a curved fissure, about 10 miles (16 km) long and 31 miles (50 km) high and of negligible width. He estimated that the central point of the fissure, the theoretical seismic centre, was 62 miles (100 km) deep. Mallet located his epicentre near the village of Caggiano, not far from Polla, but later examination of his data suggested that there was a second focus near Montemurro, about 25 miles (40 km) to the southeast.
- Burrato, P.; Valensise G. (2008). "Rise and Fall of a Hypothesized Seismic Gap: Source Complexity in the Mw 7.0 16 December 1857 Southern Italy Earthquake". Bulletin of the Seismological Society of America 98 (1). Bibcode:2008BuSSA..98..139B. doi:10.1785/0120070094. Retrieved 18 November 2010.
- Mallet, Robert (1862). Great Neapolitan Earthquake of 1857: The First Principles of Observational Seismology. Royal Society.