In this chapter, I have discussed the seismic data used in this dissertation,
their
origin, and their appearance. I have described the used velocity analysis
in Promax, which yielded an increase in velocity in the hydrate-saturated
sediments to about 1.9 km/s and a decrease in the sediments underneath to
approximately 1.7 km/s. This drop in velocity at the BSR might be
indicative of the presence of free gas in the region.
Possible RMS velocity picking errors of 
10 m/s
can result in as much as 200 m/s error in the
interval velocities, either enhancing or suppressing the observed
high and low velocity zones. The presence of an increase in
velocity in the hydrate and a subsequent decrease in a gas-saturated
zone is, however, confirmed by VSP measurements in the region.
Furthermore, the observed negative reflection
polarity at the BSR is in good agreement with a velocity reversal at the
BSR.
Subsequently, I have outlined the true-amplitude processing scheme of the data which is essential in preserving the amplitude information required for the subsequent AVO analysis. The processing scheme consisted of source wavelet deconvolution, trace interpolation, prestack migration/inversion, RNMO correction and amplitude calibration. The resulting gathers display strong, negative BSR reflection coefficients. Such amplitude trends appear to be observed at most places showing a strong BSR Andreassen et al. (1995); Hyndman and Spence (1992); Katzman et al. (1994)
After these processing steps, the final gathers are used as input into AVO inversion and modeling, which will be described in the next chapter.