Here is a comprehensive summary of the Wikipedia article on the 1138 Aleppo earthquake.

  • On 11 October 1138, a catastrophic earthquake struck the city of Aleppo in northern Syria, with a smaller foreshock occurring the day before, and is frequently listed as one of the deadliest quakes in history.
  • The staggering death toll of 230,000 reported in the 15th century is likely inaccurate, as historians believe it resulted from a conflation of this event with other major regional earthquakes in 1137 and 1139.
  • The earthquake was caused by the region's complex tectonic setting, specifically the Dead Sea Transform fault system, where the Arabian and African plates meet.
  • This was the first of two intense seismic sequences in the 12th century that devastated the war-torn Crusader states and Muslim territories of the area.
  • Modern geological estimates suggest the quake had a magnitude of Mw 7.2, triggered by a rupture along the St. Simeon Fault, and the event is well-documented by contemporary chroniclers like Ibn al-Qalanisi.