Deformation and fluid flow in sedimentary sequences cause changes in physical properties. In situ measurement of physical properties evaluates processes (consolidation, cementation, dilation) operating during deformation, fluid flow, and faulting. Because seismic images are affected by changes in physical properties, their measurement allows for calibration of seismic data as a tool for remotely sensing processes of deformation and fluid flow. Logging-while-drilling (LWD) provides an industry-standard tool for in situ evaluation of physical processes, including transient borehole conditions. Leg 171B will drill a series of LWD holes to measure the physical properties of sediments through a deforming accretionary prism and across plate-boundary faults off Barbados (Figs. 1 and 2). Extensive drilling and three-dimensional seismic surveys provide a rich framework for log interpretation, seismic calibration, and process evaluation. The results will assist with the interpretation of similar, but less active, systems in sedimentary basins elsewhere, thereby contributing to the analysis of groundwater, hydrocarbon migration, and earthquake processes.