Strong sediments at the deformation front, and weak sediments at the rear of the Nankai accretionary prism, revealed by triaxial deformation experiments.

Stipp, Michael, Rolfs, Malte, Kitamura, Yujin, Behrmann, Jan H. , Schumann, Kai, Schulte-Kortnack, Detlef and Feeser, Volker (2013) Strong sediments at the deformation front, and weak sediments at the rear of the Nankai accretionary prism, revealed by triaxial deformation experiments. Open Access Geochemistry, Geophysics, Geosystems, 114 (11). pp. 4791-4810. DOI 10.1002/ggge.20290.

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Abstract

Nineteen whole-round core samples from the Nankai accretionary prism (IODP Expeditions 315, 316, and 333) from a depth range of 28–128 m below sea floor were experimentally deformed in a triaxial cell under consolidated and undrained conditions at confining pressures of 400–1000 kPa, room temperature, axial displacement rates of 0.01–9.0 mm/min, and up to axially compressive strains of ∼64%. Despite great similarities in composition and grain size distribution of the silty clay samples, two distinct “rheological groups” are distinguished: The first group shows deviatoric peak stress after only a few percent of compressional strain (<10%) and a continuous stress decrease after peak conditions. Simultaneous to this decrease is a pore pressure increase indicating contractant behavior characteristic of structurally weak material. The second sample group weakens only moderately at a much higher strength level after significantly higher strain (>10%), or does not weaken at all. This is characteristic of structurally strong material. The strong samples tend to be overconsolidated and are all from the drillsites at the accretionary prism toe, while the weak and normally consolidated samples come from the immediate hanging wall of a megasplay fault further upslope. Sediments from the incoming plate are also structurally weak. The observed differences in mechanical behavior may hold a key for understanding strain localization and brittle faulting within the uniform silty and clayey sedimentary sequence of the Nankai accretionary prism.

Document Type: Article
Additional Information: WOS:000330531900005
Keywords: clay-rich soft sediments; failure; distributed ductile and localized brittle deformation; surface break; updip end of the seismogenic zone; NanTroSEIZE, IODP Exp. 315, 316, 333
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/ggge.20290
ISSN: 1525-2027
Projects: Future Ocean, IODP
Expeditions/Models/Experiments:
Date Deposited: 27 Nov 2013 14:45
Last Modified: 26 Apr 2019 14:16
URI: http://oceanrep.geomar.de/id/eprint/22508

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