Canadian overthrust example

The data set used for this study is a 2-D line acquired in the Canadian foothills. It has excellent signal quality and a very interesting complex structure. The similarity of nearby seismic lines, analysis of nearby wells, and success of 2-D prestack depth migration on nearby lines indicates that 3-D effects are minimal for this line.

Four representative shot gathers from the data set are plotted in Figure . There are 144 shots with 300 groups per shot. Shot and receiver spacing varies because of the rugged terrain, but the nearest offset is at 60 m, average shot spacing is 100 m, and average group spacing is 20 m. This results in 30 fold CMP coverage. Figure  is a representative plot of receiver interval for one shot gather, and Figure  is a plot of shot spacing for the entire line. The receiver spacing is fairly regular, but the shot spacing is more variable.

As shown in Figure , there is considerable topography along the line. The topography varies in excess of 200 m. That, coupled with the high near-surface velocities, makes this data set an excellent candidate for wave-equation datuming.

 

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Figure 3 Representative shot gathers from the Canadian overthrust data set

 

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Figure 4 Receiver interval along the seismic line is fairly constant. This representative plot is for shot number 50, and is typical for the line.

 

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Figure 5 Source interval along the seismic line is variable.

 

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Figure 6 Topography along the seismic line varies in excess of 200 m.