for the matrix permeability that is critical in approximating permeability structures in the
accretionary complex for modeling studies.
Hydrogeologic Modeling
Mathematical models used in hydrologic modeling are derived from the governing
principles of fluid flow and specifications such as formation geometry, boundary
conditions and initial conditions. These models help quantify conceptual models of sub-
seafloor hydrogeologic flow system. These models can be extremely useful and cost
effective in providing possible explanations for known or hypothesized conditions. They
can also be used to assess whether or not a conceptual model is feasible. As a starting
point, with limited data it is best to use one or two-dimensional analytical solutions
derived from simple well-defined boundary problems (Anderson and Woessner, 1992).
However, in sub-seafloor settings, numerical models are often necessary in order to
account for parameters such as complex geometry, variable density fluid flow, and
variations in heat flow.
Due to limited access to convergent margins, models are essential for integrating
the field observations with laboratory results. It has also been recognized that numerical
models are required in order to extend observations made at shallow parts of the
subduction system to greater depths such to the seismogenic zone (COMPLEX, 1999).
Most previous modeling studies have focused on coupled compaction-fluid flow and
diffusion-advection models of pore fluid chemistry and heat for Barbados, Nankai and
Cascadia accretionary prisms (e.g., Bekins et al., 1995; Saffer and Bekins, 2002; Screaton
and Ge, 1997). However, recent data collection allows significantly improved
characterization of permeability, which is a major component that affects modeled fluid
pressures in accretionary complexes. Furthermore, previous modeling studies at Nankai