Real Reflectivity Gather

The real reflectivity gather at the subsurface position of 49 km is shown in Figure . The BSR reflection and the one from the bottom of the gas underneath are strongly visible. The BSR displays the characteristic behavior of increasing amplitudes with increasing offset.

The actual amplitude picks along the BSR as a function of offset are shown in Figure . Anomalous amplitudes between offsets 2.25 and 2.6 km represent some residual effects present after amplitude calibration (see Chapter 2, section 2.4.3). This displayed AVO behavior was related to the presence of free gas-saturated sediment underneath the hydrate (Chapter 3). I furthermore concluded from the AVO analysis on the real data that the hydrate does not have a pronounced effect on the shear properties of the in-situ sediment. This already indicates that hydrate cementing the sediment cannot explain the seismic data from the Blake Outer Ridge.

By calculating synthetic seismograms based on the saturations inferred from seismic at the distance of 49 km and by subsequently comparing the synthetic gathers with the one in Figure , I should be able to get an better insight into the internal structure of the hydrated sediment.

 

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Figure 5 Real reflectivity gather.

 

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Figure 6 BSR AVO picks.