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doi:10.2204/iodp.proc.319.203.2015

Introduction

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a coordinated, multiexpedition drilling project designed to investigate fault slip behavior and the mechanics of seismogenesis along a subduction megathrust fault system through direct sampling, in situ measurements, and long-term monitoring associated with laboratory and numerical modeling studies (Saffer et al., 2009). As part of the NanTroSEIZE program, operations during Integrated Ocean Drilling Program (IODP) Expedition 319 included riser and riserless drilling, analyses of cuttings and core samples, downhole measurements and logging, observatory operations, and casing. Two sites were drilled during Expedition 319: Site C0009 in the Kumano forearc basin and Site C0010 across a major splay fault (termed the “megasplay”) that bounds the seaward edge of the forearc basin near its updip terminus. We analyze the grain size of samples from Site C0009, which is located at the northern edge of the 3-D seismic volume acquired in 2006 (Fig. F1).

Hole C0009A was cored from 1509.7–1593.9 meters below seafloor (mbsf). The strata in this interval are late Miocene in age and are described as brown-gray silty-claystone, with minor interbeds of brown-gray siltstone-sandstone, and minor interbeds of light gray fine vitric tuff. Four lithofacies were defined based on the relative abundance of these lithologies (see the “Site C0009” chapter [Expedition 319 Scientists, 2010]).

To create a depth profile of particle sizes at Site C0009, we analyzed the particle size distribution of 46 samples. The results may provide a useful constraint to understand how lithology impacts physical properties (e.g., permeability, compressibility, and porosity) and may assist in interpreting the paleogeographic evolution of the Kumano Basin. Our procedure and results are presented below (Tables T1, T2). A nomenclature table is included (Table T3).

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