Velocity analysis using similarity-weighted semblance

Field data examples

The first field data is a marine CMP gather (Figure 6). In this example, the proposed similarity-weighted semblance as shown in the right panel in Figure 6 obtains a very high resolution. The peaks on the semblance panel is easy to be picked out and thus reduce the velocity-peaking uncertainties (Fomel and Landa, 2014). In this example, the reference trace is chosen as the stacked trace using the SNR-weighting strategy.

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Figure 6. Comparison between semblance spectra for field data. Left: CMP gather. Middle left: using traditional semblance. Middle right: using AB semblance. Right: using similarity-weighted semblance.

The second field data example is a 3D prestack dataset from a 2D survey of the Gulf of Mexico, as shown in Figure 7. We stacked the prestack data using automatically picked NMO velocities from different semblance map. Figure 8a shows the stacked data using traditional semblance and Figure 8b shows the stacked data using the similarity-weighted semblance. The stacked data using the proposed approach can obtain better stacked result with stronger stacked energy, which indicates a more precise picked velocity. The comparison between Figures 8a and 8b is not very obvious. However, when we zoomed two parts from the original stacked sections, as shown in Figures 8c and 8d, we can find significant improvement. The two zoomed parts are highlighted by the two frame boxes in Figures 8a and 8b. In this example, the reference trace is chosen as the traditionally stacked trace.

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Figure 7. A prestack dataset from the Gulf of Mexico.

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Figure 8. (a) Stacked data using automatically picked NMO velocity from the traditional semblance. (b) Stacked data using automatically picked NMO velocity from the similarity-weighted semblance. (c) Zoomed section from (a). (b) Zoomed section from (b). The two zoomed parts are highlighted by the frame boxes in (a) and (b).

Velocity analysis using similarity-weighted semblance