1169 Sicily earthquake
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| Date | February 4, 1169 |
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| Origin time | 07:00 |
| Magnitude | 7.3 Ms |
| Epicenter | 37°13′01″N 14°57′00″E / 37.217°N 14.95°ECoordinates: 37°13′01″N 14°57′00″E / 37.217°N 14.95°E |
| Areas affected | Eastern Sicily |
| Max. intensity | X (Extreme) |
| Tsunami | Yes |
| Casualties | 15,000–25,000 deaths |
The 1169 Sicily earthquake occurred on 4 February 1169 at 07:00 on the eve of the feast of St. Agatha of Sicily (in southern Italy). It had an estimated magnitude of between 6.4 and 7.3 and an estimated maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. Catania, Lentini and Modica were severely damaged. It triggered a tsunami. Overall, the earthquake is estimated to have caused the deaths of at least 15,000 people.
Sicily's considerable seismic activity is a product of plate tectonics: the island lies on part of the complex convergent boundary where the African Plate is subducting beneath the Eurasian Plate. This subduction zone is responsible for the formation of the stratovolcano Mount Etna. Most of the damaging earthquakes occur on the Siculo-Calabrian rift zone, a zone of extensional faulting which runs for about 370 kilometres (230 mi), forming three main segments through Calabria, along the east coast of Sicily and immediately offshore, and finally forming the southeastern margin of the Hyblean Plateau, a carbonate platform in southeastern Sicily. Faults in the Calabrian segment were responsible for the 1783 Calabrian earthquakes sequence.
In the southern part of the eastern coast of Sicily, investigations have identified a series of active normal dip-slip faults, dipping to the east. Most of these lie offshore, and some control basins that contain large thicknesses of Quaternary sediments. The two largest faults, known as the western and eastern master faults, border half-grabens, with fill of up to 700 metres (2,297 ft) and 800 metres (2,625 ft) respectively. Onshore, two ages of faulting have been recognised, an earlier phase trending NW-SE and a later phase trending SSW-NNE that clearly offsets the first group, including the Avola fault and the Rosolini-Ispica fault system.
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