SIMPLE EXAMPLE

As a simple example of the methodology, we started from a single CMP gather (Figure data). We then scanned over velocities calculating semblance and instantaneous stack energy (Figure rms-picks). We started with an initial RMS velocity function $\bold d$ by picking the maximum semblance within a fairway. We used the corresponding instantaneous stack energy for our weighting function, $\bold W$.

 

data Figure 1 Input CMP gather from the Gulf of Mexico.

 

rms-picks
Figure 2 Two different approaches to picking starting RMS and weighting functions. Both start by scanning over velocity and then picking maximum amplitude within a fairway. To avoid edge problems early and late time velocities are pre-determined. The left frame shows a semblance scan and the resulting RMS function; the right panel, same information for instantaneous stack energy

We applied fitting goals (7) and (8) to the picked RMS function and obtained Figure a smooth, reasonable velocity function.

 

scale-residuals Figure 3 Estimated interval velocity obtained from fitting goals (7) and (8).