CHAPTER 2 A COMPARATIVE STUDY OF PERMEABILITY MEASUREMENTS FROM THE SUBDUCTION ZONES OF NORTHERN BARBADOS, COSTA RICA, NANKAI, AND PERU Introduction Marine sediments have been widely studied for their physical properties both in academic and industrial research. With the introduction of the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP), a new level of understanding has been added to the knowledge of marine sediments during the past few decades. Physical properties of submarine sediments have been studied largely through recovered cores, down-hole logging, and also by in situ instrumentation. Permeability is one such physical property that has been closely studied for its importance in fluid flow and pore pressures in the subsurface. Previous studies based on permeability measurements of marine sediments have suggested that correlation between permeability and porosity could provide insight to a large range of sediments in nature (Bryant, 2002). Investigations based on numerical modeling have shown that permeability is a crucial parameter in accretionary complex hydrology (e.g., Bekins et al., 1995; Bruckmann et al., 1997; Saffer and Bekins, 1998). According to Saffer and Bekins (1998) sediment permeability is the most important factor that controls modeled pore pressures because it can vary by several orders of magnitude. Thus, using a systematic relationship between porosity and permeability is a powerful way to approximate the permeability structure in an accretionary wedge model (Saffer and Bekins, 1998). Results from modeling studies have shown that pore pressures are highly sensitive to the