Neotectonics and seismicity of Algiers region

The Sahel of Algiers located between the sea and Mitidja plain is the consequence of the recent tectonics. This is an anticlinal structure of direction E-W to NE-SW which has a length of 80km. Its southern flank is marked by an escarpment which underlines abnormal contact between the Plio-Pleistocene formations of the Sahel on Quaternary formations of Mitidja. It corresponds to the seismic fault cartographically masked "blind fault" of the Sahel [Meghraoui 1988 & 1996 Maouche, 2010].

The geological evidences which can be associated with this fault are revealed by brittle deformation of metric orthogonal faults oriented N50 to 60 and N140 to N130 affecting calcarenites of Astien and sometimes Quaternary fluvial terraces of the Algiers region. The folds NE-SW reported by [Glangeaud 1952 Boudiaf, 1996] in the Pliocene levels of the Sahel and the presence of tilted terraces are associated eventually to the fault.

The historical seismicity that characterizes Algiers region is partly associated with the activity of Sahel fault. The Segment Douéra of 15km is marked by relatively well pronounced elevation of Astian deposits and a seismic activity expressed by an epicenters located on the north-eastern part, the Attatba segment with a length of 35 km has probably caused an earthquakes with high magnitudes; are identified the most active. The El-Harrach NE segment extends over a length of 30km is characterized by lower seismicity.

Keywords: Plio-quaternary deposits, neotectonic structure, seismicity, Algiers region.