Composite density displays

Steven Lynch

Over the past ten years the science of seismic visualization has progressed on all fronts except one, the display of the actual seismic data itself. We can display and animate huge 3D volumes in real time but the seismic itself is still displayed as some combination of colour/greyscale variable density with a wiggle-trace overlay.

In the first part of this paper I introduce a new type of seismic display called a Composite Density display. These new displays are the geophysical equivalent of the computer game designer's bump-mapped images. They are constructed by combining a typical variable density display with what is essentially a shaded relief map of the seismic. The resultant display is, as I will show, very similar to the truly three-dimensional SeisScape display but are much less resource intensive.

In the second part of the paper I tackle the question of "What makes a better display?" It won't take the reader long to realize that composite density displays are different but are they better? This is very hard to quantify since seismic is such a visual science and so the readers will have to make up their own minds. But to help, I present three sets of examples that cover a wider range of seismic situations.

The first example set, shows a seismic section that has been badly corrupted by migration artifacts. The variable density section shows that there are problems with the section, but the migration artifacts are very hard to see. By contrast, when the composite density's light source is oriented a certain way, the artifacts pop out of the section and are obvious to even the most unsophisticated viewer.

In the second set of examples, I tackle the nebulous subject of perception. By that I mean, "Can we use the composite density display to better understand what we can already see." The examples that were chosen, an in-line from the Stratton survey and a time slice from a Peruvian 3D are both free of processing artifacts. In both cases they were chosen because what is visible on the composite density display is also visible on the variable density display. By choosing these examples, I want the user to decide for themselves if the addition of lighting to the composite density display makes it easier to understand.

In the final set of examples, I compare the variable density and composite density views of two highly faulted seismic lines. In both cases, orienting the composite density's light source appropriately greatly enhances the viewer's ability to discern the faults. The first example has the light source perpendicular to the fault whereas the second has it parallel. This shows how important it is that the user be able to manipulate the light source in real time.