Searching for the seafloor signature of the 21 May 2003 Boumerdès earthquake offshore central Algeria
|Author(s)||Cattaneo Antonio1, Babonneau Nathalie2, Ratzov G.2, Dan-Unterseh G.2, Yelles K.3, Bracene R.6, Mercier De Lepinay Bernard4, Boudiaf A.5, Deverchere Jacques2|
|Affiliation(s)||1 : IFREMER, GM LES, F-29280 Plouzane, France.
2 : Univ Brest, IUEM, CNRS, UMR6538, F-29280 Plouzane, France.
3 : CRAAG, Algiers, Algeria.
4 : CNRS, UMR6526, F-06560 Valbonne, France.
5 : Univ Sci Montpellier2, F-34200 Sete, France.
6 : SONATRACH, Division Exploration, Boumerd`es, Algeria
|Source||Natural Hazards And Earth System Sciences (1561-8633) (Copernicus Gesellschaft Mbh), 2012 , Vol. 12 , N. 7 , P. 2159-2172|
|WOS© Times Cited||24|
|Keyword(s)||western mediterranean sea, cascadia subduction zone, turbidity current, zemmouri earthquake, sedimentary processes, submarine landslides, northern algeria, margin, gps, boundary|
|Abstract||Shaking by moderate to large earthquakes in the Mediterranean Sea has proved in the past to potentially trigger catastrophic sediment collapse and flow. On 21 May 2003, a magnitude 6.8 earthquake located near BoumerdSs (central Algerian coast) triggered large turbidity currents responsible for 29 submarine cable breaks at the foot of the continental slope over similar to similar to 150 km from west to east. Seafloor bathymetry and backscatter imagery show the potential imprints of the 2003 event and of previous events. Large slope scarps resulting from active deformation may locally enhance sediment instabilities, although faults are not directly visible at the seafloor. Erosion is evident at the foot of the margin and along the paths of the numerous canyons and valleys. Cable breaks are located at the outlets of submarine valleys and in areas of turbiditic levee overspilling and demonstrate the multi-source and multi-path character of the 2003 turbiditic event. Rough estimates of turbidity flow velocity are not straightforward because of the multiple breaks along the same cable, but seem compatible with those measured in other submarine cable break studies elsewhere. While the signature of the turbidity currents is mostly erosional on the continental slope, turbidite beds alternating with hemipelagites accumulate in the distal reaches of sediment dispersal systems. In perspective, more chronological work on distal turbidite successions offshore Algeria offers promising perspectives for paleoseismology reconstructions based on turbidite dating, if synchronous turbidites along independent sedimentary dispersal systems are found to support triggering by major earthquakes. Preliminary results on sediment core PSM-KS23 off BoumerdSs typically show a 800-yr interval between turbidites during the Holocene, in accordance with the estimated mean seismic cycle on land, even if at this stage it is not yet possible to prove the earthquake origin of all the turbidites.|