Scientific Drilling

Kinoshita, Masataka; Tobin, H. J.; Eguchi, N.; Nielsen, Simon H.H.

doi:10.2204/iodp.sd.14.03.2012

Cited by 4 publications

(2 citation statements)

References 18 publications

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“…The arrow indicates the plate convergence direction. (b) Seismic profile across the Nankai accretionary complex [after Kinoshita et al, 2012]. IODP drill sites are projected onto the profile.…”

Section: Geological Setting and Sample Descriptionmentioning

confidence: 99%

PandSwave velocity measurements of water-rich sediments from the Nankai Trough, Japan

Schumann

Behrmann

Klaeschen

et al. 2014

J. Geophys. Res. Solid Earth

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Acoustic velocities were measured during triaxial deformation tests of silty clay and clayey silt core samples from the Nankai subduction zone (Integrated Ocean Drilling Program Expeditions 315, 316, and 333). We provide a new data set, continuously measured during pressure increase and subsequent axial deformation. A new data processing method was developed using seismic time series analysis. Compressional wave velocities (V p ) range between about 1450 and 2200 m/s, and shear wave velocities (V s ) range between about 150 and 800 m/s. V p slightly increases with rising effective confining pressure and effective axial stress. Samples from the accretionary prism toe show the highest Vp, while fore-arc slope sediments show lower Vp. Samples from the incoming plate, slightly richer in clay minerals, have the lowest values for V p . V s increases with higher effective confining pressures and effective axial stress, irrespective of composition and tectonic setting. Shear and bulk moduli are between 0.2 and 1.3 GPa, and 3.85 and 8.41 GPa, respectively. Elastic moduli of samples from the accretionary prism toe and the footwall of the megasplay fault (1.50 and 3.98 GPa) are higher than those from the hanging wall and incoming plate (0.59 and 0.88 GPa). This allows differentiation between normal and overconsolidated sediments. The data show that in a tectonosedimentary environment of only subtle compositional differences, acoustic properties can be used to differentiate between stronger (accretionary prism toe) and weaker (fore-arc slope, incoming plate) sediments. Especially V p /V s ratios may be instrumental in detecting zones of low effective stress and thus high pore fluid pressure.

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Section: Geological Setting and Sample Descriptionmentioning

confidence: 99%

PandSwave velocity measurements of water-rich sediments from the Nankai Trough, Japan

Schumann

Behrmann

Klaeschen

et al. 2014

J. Geophys. Res. Solid Earth

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show abstract

“…The arrow indicates the plate convergence direction. (B) Seismic cross section along the transect of the drill sites with tectonic interpretation (after Kinoshita et al, 2012). IODP Sites C0001, C0004 and C0008 are located on both sides of the Megasplay Fault, Sites C0006 and C0007 are at the accretionary prism toe, and IODP Sites C0011 and C0012 are located on the incoming plate.…”

Section: Synchrotron Texture Measurementsmentioning

confidence: 99%

Texture development in naturally compacted and experimentally deformed silty clay sediments from the Nankai Trench and Forearc, Japan

2014

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Present‐day stress states underneath the Kumano basin to 2 km below seafloor based on borehole wall failures at IODP site C0002, Nankai accretionary wedge

Chang

Song

2016

Geochem Geophys Geosyst

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We constrain the state of stress to 2 km below seafloor in the Nankai accretionary prism at the Integrated Ocean Drilling Program (IODP) site C0002F, southwest Japan, based on borehole wall failures and rock strengths. The logging‐while‐drilling resistivity images from 872.5 to 2005.5 m below seafloor show that drilling‐mud control in riser drilling worked properly to minimize borehole wall failures. Available breakouts indicate a consistent maximum compression orientation subparallel to the subducting plate margin. Breakout analysis with drill logs suggests that breakouts occurred only when borehole pressure was slightly lowered and time lag between hole cutting and image logging was several hours. This indicates that the observed breakouts are not immediate stress‐induced failure but brought up into shape gradually with time due to other mechanisms. Laboratory investigations on deformation and failure of the cores suggest that the time‐delayed breakout might be a result of progressive rock spall‐out in borehole wall damage zones that occur at a stress level close to failure condition. We constrain stress magnitudes assuming that the stress state is sufficient to bring about the damage zones at the borehole wall. An integrated method utilizing breakouts, drilling‐induced tensile fractures, and a leak‐off test suggests that the stress states are on the boundary between strike‐slip faulting and normal faulting stress regimes, and somewhat variable depending on depth. The stress magnitudes in the accretionary wedge appear to be controlled by frictional strength of the rock, such that the differential stresses are constrained by the laboratory determined frictional coefficients.

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Scientific Drilling

Cited by 4 publications

References 18 publications

PandSwave velocity measurements of water-rich sediments from the Nankai Trough, Japan

PandSwave velocity measurements of water-rich sediments from the Nankai Trough, Japan

Texture development in naturally compacted and experimentally deformed silty clay sediments from the Nankai Trench and Forearc, Japan

Present‐day stress states underneath the Kumano basin to 2 km below seafloor based on borehole wall failures at IODP site C0002, Nankai accretionary wedge

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