In this chapter, I use the seismic amplitude information extracted by the processing described in Chapter 2 to determine the characteristics and possible causes of the BSR reflection. Using 2-D P- and S-impedance contrast inversion, the BSR appears to be characterized by negative P-impedance contrast and mostly positive S-impedance contrast. The negative P-impedance contrast is in good agreement with the velocity reversal determined in Chapter 2. Local investigation of the BSR reflection character and amplitudes shows that the BSR is underlain by many small structural layers which contribute laterally to significant tuning effects. In areas without tuning, the BSR is characterized by a strong increase in amplitude with increasing offset, while the other areas exhibit more constant amplitudes with offset. In the case of increasing amplitudes with offset, forward modeling using the Zoeppritz equations supports the BSR model of hydrate overlying free gas-saturated sediment. The more constant amplitudes with offset, on the other hand, would indicate the presence of brine-saturated sediment underneath the BSR. Although a laterally heterogeneous structure of hydrate and gas/brine distribution is physically plausible, tuning appears to be the more important factor in producing constant or distorted amplitudes in the area. This suggests that the BSR is caused by hydrate-bearing sediment overlying gas sediment. This is in good agreement with the flat reflector underneath the BSR, which appears to mark the bottom of the gas zone and the transition to brine-saturated sediments. The presence of a thick gas layer in the region of the Blake Outer Ridge has furthermore been confirmed by recent drilling results Matsumoto et al. (1996).