Lebanon

Lebanon is cut from north to south by the Yammouneh Fault, the northernmost segment of the Dead Sea Transform Fault system. This left-lateral strike-slip [[fault]] constitutes the plate boundary between the Arabian Plate to the east and the Sinai (African) microplate to the west, accommodating approximately 3–6 millimetres per year of relative motion. The fault passes through the Bekaa Valley, which is a classic pull-apart trough formed at a releasing bend in the transform system. The Mount Lebanon Range to the west and the Anti-Lebanon Range to the east form the topographic walls of this tectonic valley. The Roum Fault in southern Lebanon is a major splay of the main transform that has produced damaging historical earthquakes. Offshore, the Latakia Ridge fault system beneath the eastern Mediterranean represents additional seismic sources.

Lebanon's seismic history is rich with catastrophic events recorded across multiple millennia. The 551 AD Beirut-Tripoli earthquake, estimated at magnitude 7.5, destroyed much of the Lebanese coast and generated a [[tsunami]] that struck Alexandria and other Mediterranean ports. The famous ancient Roman law school at Beirut (Berytus) was destroyed and never rebuilt to its former glory after this event. The 1202 Syria-Lebanon earthquake (magnitude approximately 7.6) caused widespread destruction across the Levant. The 1759 earthquakes — two major events in October and November — devastated Safed, Damascus, Baalbek, and the Bekaa Valley, killing tens of thousands. Modern Lebanon has not experienced a major damaging earthquake, but the geological evidence and [[epicenter]] distribution confirm that the seismic cycle is ongoing and a future great earthquake is inevitable on the Yammouneh or Roum fault systems.

The tectonic context of Lebanon's seismicity involves the northward motion of Arabia relative to Africa, driving left-lateral shear along the Dead Sea Transform. The pull-apart geometry of the Bekaa Valley is expressed in its flat basin floor underlain by thick sediments that could amplify [[seismic-wave]] energy in future earthquakes. The thrust faulting that has uplifted the Mount Lebanon and Anti-Lebanon ranges is a secondary consequence of restraining bends along the transform system. The offshore faulting beneath the Mediterranean creates additional hazard for Lebanon's densely populated coast. Beirut, a city of approximately 2.2 million people, sits on a narrow coastal strip between the sea and the steeply rising Mount Lebanon range, with the Yammouneh Fault approximately 30 kilometres to the east — dangerously close given the expected magnitude of the next major event.