At 18:44 UTC (19:44 local time) on May 21, 2003, a strong, shallow earthquake of Moment Magnitude (M) 6.8 shook northern Algeria and caused damage in five provinces in the north-central section of the country. Damage was reported over an area about 100 km long and 35 km wide, centered on the city of Boumerdes. The hardest hit areas were in the coastal province of Boumerdes, mainly in the cities of Boumerdes, Zemmouri and Thenia. The earthquake appears to have been generated by an offshore south-dipping thrust fault oriented N54°E extending for about 35 km from Dellys to Corso. The fault rupture was bilateral, with a greater asymmetry to the southwest. The ground motions recorded from the mainshock were significantly higher than median values predicted by standard attenuation relationships. Liquefaction and lateral spreading occurred near the Isser River and areas with extensive beach sand deposits. In the port of Algiers, nine piers suffered damage where liquefaction, loss of ground support, and lateral displacement (seaward movements) of the bulkheads were pervasive. Cracks developed on the Keddara and Beni Amrane Dams and the water line running from the Keddara Dam to the Boudouaou water treatment plant suffered damage at two locations