Velocity-porosity relationships in smectite-rich sediments; Shikoku Basin, Japan

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doi: 10.1002/2013GC004974
Author(s): Tudge, Joanne; Tobin, Harold J.
Author Affiliation(s): Primary:
University of Wisconsin-Madison, Department of Geoscience, Madison, WI, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 14(12), p.5194-5207. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 87 refs.; illus., incl. sketch map
Summary: At the Nankai Trough, Japan, smectite-rich sediments of the Shikoku Basin are both underthrust beneath and frontally accreted to the outer accretionary wedge. To understand the changes that occur in the physical properties of sediments as they are underthrust or incorporated into the accretionary wedge, it is necessary to characterize those physical properties outboard of the deformation front. One key relationship to constrain is between the compressional wave velocity (vp) and porosity (Φ) in order to estimate pore fluid pressure and determine the strength of fault rocks at depth. Here we investigate how the type of clay minerals and proportions of the different clays may affect the velocity-porosity relationship, with particular emphasis on the abundance of hydrous smectitic clays. Using data from IODP Sites C0011 and C0012 in the Shikoku Basin, we demonstrate that when the core-based porosity is corrected for the abundance of smectite, the resultant velocity-porosity relationship does not fit previously established transforms. Therefore, we propose a new empirical relationship for the smectite-rich sediments of the Shikoku Basin, and caution against the indiscriminate use of global and/or pre-existing models in smectite rich formations. Abstract Copyright (2013). American Geophysical Union. All Rights Reserved.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; 07 Marine Geology and Oceanography; Asia; Clastic sediments; Clay; Clay minerals; Elastic waves; Equations; Expedition 322; Far East; Faults; IODP Site C0011; IODP Site C0012; Integrated Ocean Drilling Program; Japan; Marine sediments; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Numerical analysis; Pacific Ocean; Porosity; Sediments; Seismic waves; Sheet silicates; Shikoku Basin; Silicates; Smectite; Velocity analysis; West Pacific; X-ray diffraction data
Coordinates: N324453 N324453 E1365501 E1365501
N324944 N324945 E1365256 E1365254
N323500 N342500 E1380000 E1300000
Record ID: 2014034994
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