New constraints on oceanographic vs. seismic control on submarine landslide initiation: a geotechnical approach off Uruguay and northern Argentina

Ai, Fei, Strasser, Michael, Preu, Benedict, Hanebuth, Till J. J., Krastel, Sebastian and Kopf, Achim (2014) New constraints on oceanographic vs. seismic control on submarine landslide initiation: a geotechnical approach off Uruguay and northern Argentina Geo-Marine Letters, 34 (5). pp. 399-417.

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Abstract

Submarine landslides are common along the Uruguayan and Argentinean continental margin, but size, type and frequency of events differ significantly between distinct settings. Previous studies have proposed sedimentary and oceanographic processes as factors controlling slope instability, but also episodic earthquakes have been postulated as possible triggers. However, quantitative geotechnical slope stability evaluations for this region and, for that matter, elsewhere in the South Atlantic realm are lacking. This study quantitatively assesses continental slope stability for various scenarios including overpressure and earthquake activity, based on sedimentological and geotechnical analyses on three up to 36 m long cores collected on the Uruguayan slope, characterized by muddy contourite deposits and a locus of landslides (up to 2 km(3)), and in a canyon-dominated area on the northern Argentinean slope characterized by sandy contourite deposits. The results of shear and consolidation tests reveal that these distinct lithologies govern different stability conditions and failure modes. The slope sectors are stable under present-day conditions (factor of safety > 5), implying that additional triggers would be required to initiate failure. In the canyon area, current-induced oversteepening of weaker sandy contourite deposits would account for frequent, small-scale slope instabilities. By contrast, static vs. seismic slope stability calculations reveal that a peak ground acceleration of at least 2 m/s(2) would be required to cause failure of mechanically stronger muddy contourite deposits. This implies that, also along the western South Atlantic passive margin, submarine landslides on open gentle slopes require episodic large earthquakes as ultimate trigger, as previously postulated for other, northern hemisphere passive margins.

Document Type: Article
Additional Information: Times Cited: 0 0
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
Kiel University > Faculty of Mathematics and Natural Sciences > Institute of Geosciences
Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
ISSN: 0276-0460
Projects: Future Ocean
Date Deposited: 30 Mar 2015 11:55
Last Modified: 08 Mar 2017 11:27
URI: http://eprints.uni-kiel.de/id/eprint/27104

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