The 551 Beirut earthquake occurred on 9 July with an estimated magnitude of about 7.5 on the moment magnitude scale and a maximum felt intensity of X (Extreme) on the Mercalli intensity scale. It triggered a devastating tsunami which affected the coastal towns of Byzantine Phoenicia, causing great destruction and sinking many ships. Overall large numbers of people were reported killed, with one estimate of 30,000 by the Anonymous pilgrim of Piacenza for Beirut alone.