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Integrated Ocean Drilling Program (IODP) Expeditions 315 and 316 are part of Stage 1 of a multistage, multiexpedition effort known as the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). NanTroSEIZE is focused on drilling, sampling, and placing instruments to understand seismogenic mechanisms and faulting within the Nankai Trough subduction zone. Recovered sediments are composed of nannofossil-rich hemipelagic mud, silty and sandy turbidites, and sedimentary breccia from slope failures (see the “Expedition 315 summary” chapter [Ashi et al., 2009] and the “Expedition 316 summary” chapter [Screaton et al., 2009]).

In this study we used core samples from Sites C0001, C0004, and C0008 to investigate the megasplay fault and Sites C0006 and C0007, which are located in the frontal thrust region (Fig. F1). Recovered sediments from Site C0001 include slope-apron facies and upper accretionary prism sediments (see the “Expedition 315 Site C0001” chapter [Expedition 315 Scientists, 2009]). Cores from Sites C0004 and C0008 include slope sediments and underthrust slope facies, whereas those from Sites C0006 and C0007 included trench sediments and Shikoku Basin facies sediments (see the “Expedition 316 summary” chapter [Screaton et al., 2009]). Flow-through permeability tests were used to measure the vertical permeability of the samples. To quantify the alignment of grains on faces cut parallel to (vertical) and perpendicular to (horizontal) the core axis, samples for environmental scanning electron microscopy (ESEM) imaging of sediment fabric were located close to the whole-round cores and prepared following the general procedures described in Yue et al. (submitted).