P and S wave velocity measurements of water-rich sediments from the Nankai Trough, Japan.

Schumann, Kai, Stipp, Michael, Behrmann, Jan H. , Klaeschen, Dirk and Schulte-Kortnack, Detlef (2014) P and S wave velocity measurements of water-rich sediments from the Nankai Trough, Japan. Open Access Journal of Geophysical Research: Solid Earth, 119 (2). pp. 787-805. DOI 10.1002/2013JB010290.

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Abstract

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

Document Type: Article
Additional Information: WOS:000333034600002
Keywords: sonic velocity; Nankai; IODP; accretionary prism; NanTroSEIZE
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2013JB010290
ISSN: 0148-0227
Projects: IODP, Future Ocean
Date Deposited: 17 Jun 2014 11:50
Last Modified: 27 Feb 2018 10:28
URI: http://oceanrep.geomar.de/id/eprint/24757

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