Sediment Consolidation State and Fluid Flow Properties of Nankai Trough and Cascadia Margin Accretionary Subduction Zones

Hiroko Kitajima,

Texas A&M University, Department of Geology and Geophysics,

College Station, TX,

[email protected]

Sedimentation, deformation and fluid-flow processes operative in accretionary subduction zones are important in understanding not only mechanisms of devastating thrust-type earthquakes, often causing large tsunami, but also the accumulation of energy resources such as gas hydrates.

The project goal is to characterize the mechanical and fluid-flow properties of sediments at elevated temperature and pressure through laboratory experiments on samples recovered from Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) sites in the Nankai Trough and Cascadia Margin, which are appropriate to modeling the physics of seismic rupture, fluid expulsion, and hydrate accumulation. Three suites of experiments will be conducted; (1) measurement of hydraulic properties (porosity, permeability, and storage capacity) of sediments sampled from different lithologies at depths to constrain models of subsurface fluid flow, (2) long term consolidation tests at high pressure and high temperature to characterize physico-chemical interactions of water and minerals, and (3) deformation tests at high pressure with concurrent measurement of permeability and porosity to understand how clay-rich and high-porosity sediments deform and how fluid transport parameters change with deformation.

Understanding the relationship between deformation and fluid flow has implications for the origin, movement and accumulation of natural resources (oil, gas and hydrates) as well as environmental issues such as CO2 injection or waste isolation in deep reservoirs. Also, this study will respond to the IODP NantroSEIZE initiative to drill into the seismogenic zone of plate boundary faults in Nankai Trough by the new riser-drilling vessel Chikyu.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid