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| Titel |
Searching for the seafloor signature of the 21 May 2003 Boumerdès earthquake offshore central Algeria |
| VerfasserIn |
A. Cattaneo, N. Babonneau, G. Ratzov, G. Dan-Unterseh, K. Yelles, R. Bracène, B. Mercier de Lépinay, A. Boudiaf, J. Deverchere |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 12, no. 7 ; Nr. 12, no. 7 (2012-07-10), S.2159-2172 |
| Datensatznummer |
250010982
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| Publikation (Nr.) |
 copernicus.org/nhess-12-2159-2012.pdf |
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| Zusammenfassung |
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 Boumerdès
(central Algerian coast) triggered large turbidity currents responsible
for 29 submarine cable breaks at the foot of the continental slope over
~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 Boumerdès 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. |
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