Saudi Arabia

Saudi Arabia's seismicity is concentrated in its western and northern regions, associated with the Red Sea rift system and the Harrat volcanic fields. The Red Sea is an actively spreading ocean basin, and the Hijaz and Asir ranges along Saudi Arabia's western coast are the uplifted shoulders of this rift. Active normal [[fault]]s parallel to the Red Sea coast produce moderate earthquakes and contribute to the hazard in the Hejaz region, including near Mecca and Medina. The Harrat volcanic fields — large lava plateaus in northwestern Saudi Arabia including Harrat Rahat, Harrat Khaybar, and Harrat Lunayyir — are fed by active magmatic systems that generate both volcanic earthquakes and tectonic events associated with dyke intrusion. In 2009, a swarm of over 30,000 earthquakes at Harrat Lunayyir preceded what seismologists interpreted as an incipient volcanic eruption that was averted by evacuation and careful monitoring.

Saudi Arabia's seismic history includes the 1915 Hejaz earthquake, the 1941 Al-Qunfudhah earthquake (magnitude 6.8), and numerous events associated with the Harrat volcanic fields. The 2009 Harrat Lunayyir earthquake swarm produced a magnitude 5.7 mainshock and caused the evacuation of Al-Ays town. Aqaba Gulf events — including the 1995 Gulf of Aqaba earthquake (magnitude 7.2) that killed 12 people in southern Saudi Arabia — demonstrate the hazard associated with the northward extension of the Red Sea rift system. Eastern Saudi Arabia, including Riyadh and the oil-producing Eastern Province, sits on the stable Arabian Platform interior and experiences much lower hazard, though [[seismic-wave]]s from distant Zagros earthquakes are occasionally felt.

The tectonic setting of Saudi Arabia involves the progressive rifting of the Arabian Plate from the African Plate as the Red Sea spreads wider. This rifting began approximately 30 million years ago and continues today at roughly 15–20 millimetres per year along the main Red Sea rift axis. The Arabian Plate is not only rifting from Africa but also rotating slightly, with the northern end opening into the Gulf of Suez and the Gulf of Aqaba. The Jordan-Dead Sea rift system continues the tectonic boundary northward through Jordan and into Lebanon and Syria. The Harrat volcanic fields are fed by mantle upwelling associated with the rifting, creating a unique combination of volcanic and tectonic seismic hazard in western Saudi Arabia that requires ongoing monitoring by the Saudi Geological Survey.