pressure and P = lithostatic pressure) were 0.50 (Foucher, et al., 1997) and 0.36 (Becker

et al, 1997), respectively. These results were similar to those previously obtained using a

steady state model with a permeability-depth relation for clay-rich sediments (Bekins et

al; 1995). Moreover, the increase of ~* by 0.15 between Sites 949 and 948 over a lateral

distance of 2.2 km was also estimated by Stauffer and Bekins (2001) based on inferred

consolidation state.

 In addition, constraints for pore pressure distribution also follow from an analysis

of the mechanical force balance in accretionary wedges presented by Davis et al. (1983).

According to Davis et al. (1983), in order for the sediments of the wedge to move over

the underthrust sequence along a low-angle decollement, high pore pressures (k = 0.92

for the overall taper, where X is the ratio of pore fluid pressures to the vertical normal

traction exerted by the lithostatic overburden) must be present along the decollement.

The presence of lower pressures would result in a steeper taper angle than that observed

at Barbados (Bekins et al., 1995).

Hydrofractures

 Behrmann (1991) suggested that hydrofracturing enhances permeability in

argillaceous rock sequences. According to Behrmann (1991) the capability of rocks to

hydrofracture depends on the mode of faulting and the effective mean stress. He also

noted that the depth to which hydrofracture could occur is a function of both the faulting

mode and the ratio of fluid and lithostatic pressures. Thus, wrench and normal faults

hydrofracture even at ratios of fluid and lithostatic pressure is less than one. In contrast

thrust faults always require ratio of fluid and lithostatic pressure to be greater than one to

hydrofracture. Vertical fluid flow has been indicated by 3 -D seismic images at the