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Medientyp:
E-Artikel
Titel:
Geotechnical in situ characterization of subaquatic slopes: The role of pore pressure transients versus frictional strength in landslide initiation
Erschienen:
American Geophysical Union (AGU), 2007
Erschienen in:
Geophysical Research Letters, 34 (2007) 7
Sprache:
Englisch
DOI:
10.1029/2006gl029122
ISSN:
0094-8276;
1944-8007
Entstehung:
Anmerkungen:
Beschreibung:
Mineralogical composition and pore fluid pressure are the crucial controls for mechanical stability of water‐saturated sediments. Their in situ measurements were undertaken in earthquake‐triggered slope deposits in Lake Lucerne (Switzerland) in addition to geophysical characterization and laboratory index properties, shear and consolidation experiments on core. Two lithological units were identified: A weak, lightly underconsolidated section of postglacial silty clays overlies overconsolidated fine‐grained glacial deposits with coarser components and excess fluid pressure (ca. 2.5× higher than in the hanging wall clay). In the event of an earthquake, hydrofracturing in the overconsolidated section facilitates an upward pore pressure pulse to the base of the softer, less stable unit. Here, excess pore pressure initiates sliding along a failure plane at the lithological boundary, causing the entire postglacial sedimentary section to slip downslope. We propose that many submarine landslides at active and passive continental margins may follow this mechanism of pore pressure‐induced failure.