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  | isbn    = 0-89181-602-X

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From the broad field of seismology, a few things seem to pop up with regularity. Some of these have been collected here. Keep them in mind when working with seismic data—in particular, 3-D seismic data.

From the broad field of seismology, a few things seem to pop up with regularity. Some of these have been collected here. Keep them in mind when working with [[seismic data]]—in particular, 3-D seismic data.

==The onion==

==The onion==

[[file:interpreting-seismic-data_fig12-2.png|300px|thumb|{{figure number|2}}. Copyright: Liner;<ref name=Liner /> courtesy PennWell.]]

[[file:interpreting-seismic-data_fig12-2.png|300px|thumb|{{figure number|2}}. Copyright: Liner;<ref name=Liner /> courtesy PennWell.]]

If you look at a [http://www.merriam-webster.com/dictionary/outcrop rock outcrop], you see [[sandstone]], [[shale]], [[limestone]], etc. If you look at seismic data, you see the edges of rock units. The figure below shows the edge effect on a Gulf of Mexico [[salt dome]] example. Seismic analysis is, in effect, an edge detection technique. The bigger the [[velocity]] and/or [[density]] contrast between the rocks, the stronger the edge.

If you look at a [http://www.merriam-webster.com/dictionary/outcrop rock outcrop], you see [[sandstone]], [[shale]], [[limestone]], etc. If you look at seismic data, you see the edges of rock units. The figure below shows the edge effect on a [[Gulf of Mexico]] [[salt dome]] example. Seismic analysis is, in effect, an edge detection technique. The bigger the [[velocity]] and/or [[density]] contrast between the rocks, the stronger the edge.

To be fair, seismic impulses respond to much more than just lithology. Any vertical variation in rock property that modifies the velocity or density can potentially generate [[seismic reflection]]s, including a [[Fluid contacts|fluid contact]], [[porosity]] variation, or shale density change.

To be fair, seismic impulses respond to much more than just lithology. Any vertical variation in rock property that modifies the velocity or density can potentially generate [[seismic reflection]]s, including a [[Fluid contacts|fluid contact]], [[porosity]] variation, or shale density change.

==Event tracking==

==Event tracking==

A key part of the interpretation process for 3-D seismic data is event tracking. To picture this, think of the [[3-D seismic: the data cube|3-D seismic data volume]] as a block of vanilla ice cream with chocolate streaks. Tracking means we follow a streak into the cube and find out where it goes—this is [[Seismic structure map|structure mapping]]. We also keep track of how dark the chocolate is as we follow it—this is [[amplitude map]]ping.

A key part of the interpretation process for 3-D [[seismic data]] is event tracking. To picture this, think of the [[3-D seismic: the data cube|3-D seismic data volume]] as a block of vanilla ice cream with chocolate streaks. Tracking means we follow a streak into the cube and find out where it goes—this is [[Seismic structure map|structure mapping]]. We also keep track of how dark the chocolate is as we follow it—this is [[amplitude map]]ping.

==Computer limitations==

==Computer limitations==

[[Category:Interpreting seismic data]]

[[Category:Interpreting seismic data]]

[[Category:Geophysical methods]]

[[Category:Geophysical methods]]