The Yammouneh Fault is the main branch of the Dead Sea Transform where that plate boundary crosses Lebanon, forming a restraining bend that helped raise the Mount Lebanon range. It is a left-lateral strike-slip fault along which the Arabian Plate slides northward past the African (Sinai) Plate, running through the fertile Beqaa region.
Because the fault bends here, plate motion is partly converted into compression and uplift, which explains why Lebanon's mountains stand so high beside an otherwise horizontal transform. The fault threads past ancient sites and the Yammouneh basin, and its trace has been mapped in offset streams and ridges across the highlands.
Historically the Lebanese segment of the transform has produced destructive earthquakes, including the great 1202 event that damaged cities across the Levant, and it is linked to the coastal disasters that struck Beirut and Baalbek in antiquity. Long quiet intervals mean the fault stores strain for future large earthquakes beneath a heavily populated region.