At 7:44 p.m. on 21 May 2003, a magnitude 6.8 earthquake struck the coast near Zemmouri and Boumerdès, about 50 km east of Algiers, rupturing a previously unmapped offshore thrust fault beneath the Mediterranean Sea in Algeria's Tell Atlas region.
Algeria's Civil Protection agency confirmed 2,266 deaths, with roughly 11,000 injured and about 200,000 left homeless. Casualties were concentrated in poorly reinforced multi-storey concrete apartment blocks in Boumerdès, Zemmouri and the eastern suburbs of Algiers, many of which collapsed due to substandard construction and weak ground floors — the same failure pattern seen in earlier Algerian earthquakes.
The offshore rupture also triggered a small but well-documented tsunami that crossed the western Mediterranean, with a run-up of about 2 metres recorded in the Balearic Islands, Spain, where it damaged boats in Menorca's harbour — one of the few instrumentally confirmed tsunamis ever recorded in that sea.
The disaster exposed weak enforcement of the seismic building code Algeria had adopted after the 1980 El Asnam earthquake and led to a tightened national paraseismic regulation (RPA) afterward. Algeria's Centre de Recherche en Astronomie, Astrophysique et Géophysique (CRAAG) still monitors the Tell Atlas's many offshore thrust faults, most of which remain incompletely mapped and pose an ongoing tsunami risk to the whole western Mediterranean coast.