An earthquake with an estimated magnitude of 7.9 struck the eastern Alborz mountains in Persia, causing an estimated 200,000 deaths. 856 Damghan earthquake: The Damghan earthquake or the Qumis earthquake occurred on 22 December 856 in Khorasan province, Abbasid Caliphate. The earthquake had an estimated magnitude of 7.9, and a maximum intensity of X (Extreme) on the Mercalli intensity scale. The meizoseismal area extended for about 350 kilometres (220 mi) along the southern edge of the eastern Alborz mountains of present-day Iran including parts of Tabaristan and Gorgan. The earthquake's epicenter is estimated to be close to the city of Damghan, which was then the capital of the Persian province of Qumis. It caused approximately 200,000 deaths and is listed by the United States Geological Survey as the sixth deadliest earthquake in recorded history. This death toll has been debated. December 22, 856. Wiki link