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doi:10.2204/iodp.proc.322.208.2013

Introduction

During Integrated Ocean Drilling Program (IODP) Expedition 322, research was conducted to understand the sedimentology, physical properties, and sediment and fluid chemistry of input sediments to the Nankai accretionary complex and subduction zone (see the “Expedition 322 summary” chapter [Underwood et al., 2010]). The research objectives of Expedition 322 are part of the overall research objectives of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) to constrain, monitor, and understand faulting and seismogenesis along megathrusts (Tobin and Kinoshita, 2006).

To contribute to the NanTroSEIZE research objectives, we calculated the permeability (k) of input sediments to the subduction zone. We subsampled whole-round samples collected from IODP Sites C0011 and C0012 (Fig. F1) during Expedition 322 for constant rate of strain (CRS) consolidation experiments and flow-through permeability experiments to estimate permeability. Original whole-round samples and experimental subsamples were hemipelagic mudstone, as determined by shipboard and shore-based inspection. We focused on hemipelagic mudstones to constrain the bulk behavior of one lithologic type. We completed seven vertical permeability calculations for specimens from Site C0011, eight vertical permeability calculations for specimens from Site C0012, and four horizontal permeability calculations for specimens from Site C0012 (Table T1). These data help define the permeability behavior at Site C0011 from 366.76 to 687.15 meters below seafloor (mbsf) and at Site C0012 from 115.44 to 473.11 mbsf. These results complement other permeability analyses within NanTroSEIZE (Boutt et al., 2012; Dugan and Daigle, 2011; Ekinci et al., 2011; Guo et al., 2011; Hüpers and Kopf, 2012; Ikari et al., 2009; Reuschle, 2011; Rowe et al., 2011; Saffer et al., 2011; Yue et al., 2012). Flow properties studies can be coupled with grain-size and sedimentological studies (e.g., Kopf et al., 2011; Guo and Underwood, 2012) to help define the relation between lithology and permeability (e.g., Schneider et al., 2011). The permeability behavior is also integral to numerical modeling studies aimed at understanding the coupling of deformation and fluid flow within the NanTroSEIZE accretionary complex (e.g., Rowe et al., 2012). Numerical models using laboratory results as inputs and constraints can be used to understand the fluid budget of the Nankai accretionary complex and its input sediments. This also helps constrain solute and energy transport in the Nankai Trough region. The integration of numerous geotechnical, sedimentological, and hydrological studies through the NanTroSEIZE project will contribute to our knowledge of the coupling between flow, deformation, and strength in accretionary complexes.

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