The 1138 Aleppo earthquake was among the deadliest earthquakes in history. Its name was taken from the city of Aleppo, in northern Syria, where the most casualties were sustained. The quake occurred on 11 October 1138 and was preceded by a smaller quake on the 10th. It is frequently listed as the third deadliest earthquake in history, following on from the Shensi and Tangshan earthquakes in China. However, the figure of 230,000 dead is based on a historical conflation of this earthquake with earthquakes in November 1137 on the Jazira plain and the large seismic event of 30 September 1139 in the Transcaucasia city of Ganja. The first mention of a 230,000 death toll was by Ibn Taghribirdi in the fifteenth century.
Aleppo is located in northern Syria. The region, which sits on the boundary between the Arabian geologic plate and the African plate, is part of the Dead Sea Fault system. In the early 12th century this ancient Muslim city was home to tens of thousands of residents. On Oct. 10, 1138, a small shock shook the region, and some residents fled to surrounding towns. The main quake occurred the following day. As the city walls crumbled, rocks cascaded into the streets. Aleppo’s citadel collapsed, killing hundreds of residents.
Damaged Red Cross and Arab Red Crescent medical supplies are seen in a warehouse in the town of Urum al-Kubra on the western outskirts of the northern Syrian city of Aleppo on September 20, 2016, the morning after a convoy delivering aid was hit by a deadly
https://en.wikipedia.org/wiki/1138_Aleppo_earthquake#Description / http://blogs.sha613.org/shoshanab17/2015/02/03/1138-aleppo-syria-earthquake/