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doi:10.2204/iodp.proc.338.202.2015

Introduction

Integrated Ocean Drilling Program (IODP) Expedition 338 was designed to extend and case riser Hole C0002F from 856 to 3600 meters below the seafloor (mbsf). Due to damage to the intermediate flex joint of the riser system, Expedition 338 suspended operations in Hole C0002F at 2005.5 mbsf and continued with riserless operations at Sites C0002, C0012, C0018, C0021, and C0022 (Moore et al., 2014; Strasser et al., 2014a). Expedition 338 was part of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), a multiexpedition scientific project to investigate fault mechanics and seismogenesis along a subduction megathrust, which includes the goals to understand faulting, deformation, and hydrological processes in the vicinity of the plate boundary and megasplay faults along the Nankai convergent margin (Tobin and Kinoshita, 2006).

At Site C0002 (Fig. F1), the specific scientific objectives were to sample the Kumano forearc basin sediment and gas hydrate zone, to examine the Kumano forearc basin-accretionary prism unconformity, and to sample the upper portion of the inner wedge of the accretionary prism. Data and samples were collected to characterize the gas hydrate zone; to define the composition, age, and stratigraphy; to investigate the mechanical and hydrologic properties of the system; and to characterize the overall structural evolution of the accretionary prism.

To help define the physical and hydrological properties of sediment of Site C0002, I performed mercury injection capillary pressure (MICP) measurements on bulk cuttings (>4 mm fraction) and core samples. This work complements other geotechnical and sedimentological work within the NanTroSEIZE project to help understand fluid flow, solute/heat transport, and overpressure in the Nankai convergent margin system (e.g., Guo et al., 2013; Ikari et al., 2009; Kitajima et al., 2012; Rowe et al., 2012; Schumann et al., 2014; Tobin and Saffer, 2009).

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