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doi:10.2204/iodp.proc.314315316.208.2011

Introduction

Integrated Ocean Drilling Program (IODP) Expedition 316 conducted research to understand deformation, fault zone properties, structural partitioning, and fluid flow in the frontal thrust and shallow zone of the megasplay of the Nankai subduction zone (see Screaton et al., 2009). The goals of IODP Expedition 316 fit within the larger objectives of the multiphase Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) to constrain, monitor, and understand faulting and seismogenesis along megathrusts (Tobin and Kinoshita, 2006).

We focus on the consolidation and flow behavior of shallow sediments, which will be integrated with other shore-based research to understand fluid budgets and deformation of sediments within the Nankai accretionary complex. Whole-round samples were used in constant-rate-of-strain (CRS) consolidation experiments to measure the compression behavior and to estimate the in situ flow properties. Vertically and horizontally oriented specimens from Expedition 316 Sites C0004 and C0006–C0008 were tested to constrain anisotropy of bulk sediment properties in the shallow (<100 meters below seafloor [mbsf]) subsurface (Table T1). We also completed grain-size analysis of geotechnical samples (Table T1) for comparison with geotechnical properties. Our results complement grain-size, sedimentological, consolidation, and permeability analyses that are ongoing throughout the NanTroSEIZE project. Integrated studies from NanTroSEIZE will provide a full suite of geotechnical and sedimentological parameters to help us understand coupling between flow, deformation, and stability and can be used for inputs into basin-scale models.

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