Figure 1 is a cross-sectional profile illustrating a chute or fault surface low geometry, If the fault surface dips at a steep angle, then as the hangingwall moves over the footwall the entire hangingwall drops a large vertical distance (Figure 1), If however, the fault surface dips at a gentle angle, then as the hangingwall moves over the footwall the entire hangingwall drops a smaller vertical distance than it does over a fault that has a fault chute geometry. This difference in vertical distance can be seen by comparing the top of the rollover in Figures 1 and 2, The net effect, of the hangingwall block motion along the strike of a fault with this type of changing geometry, is to create a saddle or syncline over the fault chute geometry and a closed rollover high over the fault flat or bow geometry (Figure 3).

The relationship shown in Figures 1 and 2 between the fault chute and the fault bow geometry has application when generating or evaluating prospects, and can rapidly direct you to the rollover high. When evaluating a prospect, line up the dip lines in consecutive order. Then examine each line that crosses the prospect. The line that contains the flattest or lowest gradient on the fault surface should cross near the crest of the mapped rollover high, The dip lines that have the steepest fault surface dips should cross the saddles that laterally close the rollover (Figure 3), If the line that contains the flattest fault surface does not cross near the crest of the mapped rollover high, then the crest of the structure may not be correctly located. If a fault surface map has been prepared for the prospect, then the structure map can be laid over the fault surface map. The structural high should lie directly over or slightly down dip of a bow or high on the fault surface map. The size of the prospect should also approximate the size of the bow on the fault surface map. A comparison of the fault surface and structure maps is a good consistency check that helps to ensure prospect integrity.