Historic Earthquakes: Tectonic Summary

Magnitude 6.8 NORTHERN ALGERIA
2003 May 21 18:44:19 UTC

The earthquake occurred in the boundary region between the Eurasian plate and the African plate. Along this section of the plate boundary, the African plate is moving northwestward against the Eurasian plate with a velocity of about 6 mm per year. The relative plate motions create a compressional tectonic environment, in which earthquakes occur by thrust-faulting and strike-slip faulting. Analysis of seismic waves generated by this earthquake shows that it occurred as the result of thrust-faulting.

Algeria has experienced many destructive earthquakes. On October 10, 1980, the city of El Asnam (formerly Orleansville and today Ech-Cheliff) was severely damaged by a magnitude 7.1 earthquake that killed at least 5000 people. The site of El Asnam is situated approximately 220 km to the west of the recent earthquake. The same city, as Orleansville, had been heavily damaged on September 9, 1954, by a magnitude 6.7 earthquake that killed over 1000 people. On October 29, 1989, a magnitude 5.9 earthquake struck about 110 km to the west of the recent earthquake and killed at least 30 people.