Formation, segmentation and deep crustal structure variations along the Algerian margin from the SPIRAL seismic experiment

The Algerian continental margin in the western Mediterranean formed as a back-arc basin and is today reactivated by convergence between African Eurasian plates. It one of very rare examples passive margins undergoing inversion expressed moderate seismicity possibly giving way for future subduction. With objective to better know deep structure its associated basin, origin study mechanism reactivation, five existing wide-angle seismic profiles along are revisited. They were located offshore Mostaganem, Tipasa, Greater Kabylia, Jijel Annaba. These show that underlain 5 km thick crust oceanic magmatic origin, created at non-continuous small accretionary ridge segments. continent-ocean transition zone narrow, except easternmost profile, due an opening including shear movement. No high velocity lower corresponding mantle rocks has been imaged margin. thinned narrow strongly segmented manner. widest (70 km) central segment Kabylia where there wider distal than on other thickest detected during this survey corresponds Kabylides blocks about 22–25 thick. This reduced thickness comparison with unthinned might be influence earlier subduction margin, form erosion subducting slab.