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Deformation and mechanical strength of sediments at the Nankai subduction zone: implications for prism evolution and decollement initiation and propagation
Department of Earth Science, Rice University, Houston, TX.
Department of Earth Science, Rice University, Houston, TX.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
2007 (English)In: The Seismogenic Zone of Subduction Thrust Faults: [MARGINS Theoretical Institute on "The Seismogenic Zone Revisited", held at Snowbird, Utah, March 16 to 21, 2003], New York: Columbia University Press, 2007, 210-256 p.Chapter in book (Other academic)
Abstract [en]

As in many depositional settings, marine sediments at convergent margins undergo diagenetic changes before, during, and after mechanical consolidation and deformation. These changes influence mechanical behavior within and beneath the prism and along the décollement. To illustrate the interrelations between sediment diagenesis and deformation, we review physical properties and the types and distributions of deformation structures at several ODP and DSDP drill sites from the frontal regions of the Nankai accretionary prism. Both compactive and dilative deformation structures and fabrics are documented, denoting complicated stress paths during consolidation and tectonic deformation. Laboratory deformation experiments conducted on selected samples from these sites also demonstrate enhanced sediment strengths relative to their preconsolidation stress, both above and below the décollement horizon. This mechanical response indicates the presence of intergranular bonding or cementation that allows sediments to resist consolidation and deformation to relatively high stresses. Once their shear strengths are exceeded, however, cemented sediments can undergo rapid failure, leading to transient increases in pore pressures followed by consolidation. This deformation history may account for the localized compactive deformation bands within the prism. An analogous sequence may develop at depth within the underthrust sediments. Stress perturbations, e.g., near the up-dip limit of the seismogenic zone, may locally exceed the enhanced shear strengths of the underthrust sediments, leading to compactive failure and release of trapped pore fluids. Associated increases in pore fluid pressures may enable décollement downcutting and tectonic underplating. The resulting changes in structural and physical properties of the sediments may favor the onset of seismogenic slip along the décollement

Place, publisher, year, edition, pages
New York: Columbia University Press, 2007. 210-256 p.
, MARGINS Theoretical and Experimental Earth Science Series
Research subject
Mining and Rock Engineering
URN: urn:nbn:se:ltu:diva-21431Local ID: e8d2c730-78ab-11db-962b-000ea68e967bISBN: 978-0-231-13866-6OAI: diva2:994477
Godkänd; 2007; 20061120 (ysko)Available from: 2016-09-29 Created: 2016-09-29Bibliographically approved

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