--> Shaded Relief Display of Seismic Image, by Arthur E. Barnes, #40599 (2010)
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GCShaded Relief Display of Previous HitSeismicNext Hit Images*

 

Arthur E. Barnes1

 

Search and Discovery Article #40599 (2010)

Posted September 30, 2010

 

*Adapted from the Geophysical Corner column, prepared by the author, in AAPG Explorer, March, 2010, and entitled “Shining Light on a Shady Situation”. Editor of Geophysical Corner is Bob A. Hardage ([email protected]). Managing Editor of AAPG Explorer is Vern Stefanic; Larry Nation is Communications Director.

 

1Landmark Graphics Corp., Highlands Ranch, Colorado ([email protected])

 

 

General Statement

 

Previous HitSeismicNext Hit reflection data come alive when displayed with shaded relief. With shaded relief, time slices look like illuminated topography, and Previous HitverticalNext Hit sections look like rugged canyon walls; faults, domes, anticlines, synclines, channels and even gas clouds stand out boldly.

 

Shaded relief displays are ubiquitous in geology and geophysics. Elevations, bathymetry, gravity, magnetic and other kinds of map data are routinely displayed with shaded relief to make maps that look like photographs of apparent topography. Such maps are powerful aids to geologic intuition because apparent topography often suggests true underlying geology. Though contour maps offer the same information, shaded relief maps present the information in a way that is more natural – and so more readily comprehensible.

 

Figures

 

General statement
Figures
Method
Conclusion




















General statement
Figures
Method
Conclusion




















General statement
Figures
Method
Conclusion




















General statement
Figures
Method
Conclusion

 

 

 

 

 

 

 

fig01

Figure 1. Previous HitSeismicNext Hit data + shaded relief attribute = illuminated Previous HitseismicNext Hit reflections.

fig02

Figure 2. A cross-section as it would appear if imaged by Previous HitseismicNext Hit data and converted to Previous HitseismicNext Hit shaded relief. At any point on a reflection surface, the illumination is a function of the angle of incidence of the light upon the surface.

fig03

Figure 3. (a) Time slice through the Previous HitseismicNext Hit data volume of Figure 1; (b) the same time slice blended with shaded relief. The yellow arrow indicates the direction of illumination. The anticlinal structure stands out sharply, even though the crest is obscured by a gas cloud.

fig04

Figure 4. Previous HitSeismicNext Hit shaded relief is best viewed along time slices or horizons, but it can also be effective in Previous HitverticalNext Hit view. (a) A highly faulted zone through the Previous HitseismicNext Hit data of Figure 1; (b) the Previous HitseismicNext Hit data blended with shaded relief. The yellow arrow indicates the direction of illumination. Faults appear sculpted into the side of the volume and tend to be clearer.

 

Method and Examples

 

Adding shaded relief to 3D Previous HitseismicNext Hit data is similar to adding shaded relief to maps, with the difference that shading is applied to all reflection surfaces in the Previous HitseismicNext Hit volume, not to a single horizon. Thus Previous HitseismicNext Hit shaded relief is inherently 3D, so that both time slices and Previous HitverticalNext Hit sections appear illuminated. The process of adding shaded relief to Previous HitseismicNext Hit data is simple: create a shaded relief Previous HitseismicNext Hit attribute and blend it with the Previous HitseismicNext Hit data (Figure 1).

 

A shaded relief Previous HitseismicNext Hit attribute quantifies the amount of light that Previous HitseismicNext Hit surfaces reflect when illuminated by a distant light source (Figure 2). This quantity – the shading – is a function of the angle of incidence of the illumination, which depends on reflection orientation and the position of the sun. Shading can be controlled by exaggerating reflection slopes to enhance contrasts, or by adjusting surfaces to appear dull like shale, shiny like water or moderately shiny like quartz sand. Because shaded relief depends on the sun position, it acts as a directional filter.

 

Features that trend perpendicular to the illumination direction are highlighted, while features that trend parallel are hidden. To capture all trends, it is necessary to create two shaded relief attribute volumes using orthogonal illumination directions. Blending Previous HitseismicNext Hit data with shaded relief complements blending data with a discontinuity attribute because shaded relief reveals different structural features than continuity, principally anticlines, synclines and domes (Figure 3).

 

Like discontinuity, shaded relief also reveals faults and channels (Figure 4), with the advantage that it can indicate the direction of throw on a fault and show the internal geometry of the channel. A shaded relief Previous HitseismicNext Hit attribute can have arbitrary resolution, but it tends to provide better results when it is fairly smooth and clean (as in the data examples presented here). Smoothed shaded relief highlights large features and trends that might otherwise be obscured by details in the data; it lets one see the forest for the trees. In this way shaded relief can serve as a useful tool for rapid reconnaissance of structure in a Previous HitseismicNext Hit volume. Of course, smoothing reduces the resolution of the shaded relief so that small features, such as narrow channels and minor faults, will not be seen. These features are often best imaged by discontinuity and curvature attributes.

 

Conclusion

 

Almost everything we do to prepare Previous HitseismicNext Hit data for conventional interpretation is designed to make images that look as much like geology – and as little like Previous HitseismicNext Hit waves - as we can. Previous HitSeismicNext Hit shaded relief is another small step in this direction. Can shaded relief aid our understanding of Previous HitseismicTop data as much as it aids our understanding of geologic maps? Only time will tell.

 

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