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