Variations in log-derived physical properties among tectonic domains at the Nankai Trough, Japan; IODP NanTroSEIZE Project

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Author(s): Tudge, J.; Tobin, H. J.
Author Affiliation(s): Primary:
University of Wisconsin-Madison, Department of Geosciences, Madison, WI, United States
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Characterising physical properties at subduction zones is essential to understanding the changes that occur as sediments are subducted and incorporated into accretionary prisms. The relationship between compressional wave velocity and porosity is key to quantifying the fluid and solid material budget in the subduction process because velocity can be remotely sensed. That relationship is intrinsically linked to the burial history and tectonic evolution of sediments. Typically, core-derived velocity and porosity data have been used to develop transform functions; however, they often require corrections for in-situ conditions and are rarely complete data sets, especially in and around fault zone settings. Borehole logging data is continuous through fault zones and measures at in-situ conditions, and therefore provides a good alternative to core data. Using data from recent IODP drilling expeditions for the NanTroSEIZE drilling project, we use logging data to investigate variations in the physical properties based on tectonic regime and the associated inferred sediment burial and deformational history. Our studies focus on data from Sites C0002 and C0009, which are located in the Kumano forearc basin and extend down into the underlying older accretionary prism. Initial results indicate that previous empirical relationships between compressional wave velocity and porosity for similar settings do not apply in detail. However, a distinctly different relationship between velocity and porosity is observed between the Kumano forearc basin sediments and the underlying accretionary prism, consistent with their different tectonic histories. By investigating the variations in physical properties across the Nankai Trough we can make inferences about the tectonic evolution of the sediments in different areas across the Nankai Transect. By establishing locally calibrated empirical relationships between velocity and porosity we provide a potential means of expanding porosity models away from the borehole and onto the seismic scale. In addition, we also investigate the diagnostic potential of these relationships for determining the tectonic history of both stratigraphic and structural packages.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Accretionary wedges; Basins; Expedition 319; Fault zones; Faults; Fore-arc basins; IODP Site C0002; IODP Site C0009; Integrated Ocean Drilling Program; Kumano Basin; Models; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Pacific Ocean; Physical properties; Plate tectonics; Porosity; Porous materials; Sediments; Stratigraphy; Subduction; Subduction zones; Tectonics; West Pacific
Coordinates: N331800 N331801 E1363801 E1363800
N332728 N332728 E1363209 E1363209
Record ID: 2015077230
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