Detailed Analysis of a Submarine Landslide (SAR-27) in the Deep Basin Offshore Algiers (Western Mediterranean)

摘要: On May 21, 2003 an earthquake with a magnitude of 6.8 (Mw) struck the city Boumerdes, located on coast near Algiers, and generated significant gravity flows recognized by numerous submarine cable breaks. In order to investigate possible offshore imprint past earthquakes in terms sediment instabilities, we analyzed one escarpments tectonic origin existing Algerian margin. This escarpment, about 50 km NE Algiers is within water depths between 2,600–2,900 m has average slope 4°. A variety geotechnical (piezocone), geophysical (swath bathymetry, Chirp echo-sounder high-resolution deep-towed side scan sonar) sedimentological (sediment cores) techniques were used realize this work. Our study focuses well-defined landslide scar (called SAR27) revealed side-scan sonar images. The SAR 27 slide small size (0.5 × 1.7 km), but exhibits complex morphology including 10-m high headwall scar, tilted blocks, area reworked distal deposit. Correlations in-situ measurements, sampling CHIRP profile provided comprehensive understanding geometry emphasized role thin silty sand beds initiation. These are probably acting as liquefied slip surfaces, implying translational displacement mode which correlates morphology.