On 4 September 1169, a violent earthquake struck Catania, the eastern coast of Sicily and southern Calabria. The epicentre was in the Ionian Sea, between the cities of Catania and Syracuse. The tremor reached the 10th degree on the Mercalli scale, while the magnitude is estimated at 7.5. There was serious damage in Catania, where the cathedral collapsed during the Mass of Aurora in honour of the patron Saint Agatha, celebrated on 5 February. The death toll was estimated to be between 15,000 and 20,000.