| [[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 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. |