Structural analysis and interpretation of the surface deformations of the El Asnam Earthquake of October 10, 1980

The El Asnam earthquake of October 10, 1980, represents the major seismotectonic event of these last decades in the West Mediterranean area. It has induced a large amount of surface breaks. This earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of North Africa. The tectonic analysis of surface rupture shows the complexity of the deformation mechanism. The principal mechanism consists of the activation of a NW‐SE trending thrust fault, accompanied with a left‐lateral motion and with an intense deformation of the northwestern overthrusting block. An accurate description of these deformations shows that, for a large part, the breaks geometry depends closely on the substratum structure. Finally, the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation.