How do polarity and amplitude variations of seismic images relate to variations in fluid pressure, permeability, and other sediment physical properties? If these questions can be answered, seismic data can be used as a predictor of fluid properties in fault zones. Once applied, these data can be used to study earthquake hazards and hydrocarbon and groundwater migration. Shallowly dipping decollement faults (detachments thrusts) beneath accretionary prisms formed at convergent margins are ideal locations for calibrating seismic reflection images as proxies for fluid processes [Shipley etal, 1994] (Figure 1).