Changes

[[file:interpreting-seismic-data_fig12-2.png|thumb|{{figure number|2}}. Copyright: Liner, 1999; courtesy PennWell.]]

[[file:interpreting-seismic-data_fig12-2.png|thumb|{{figure number|2}}. Copyright: Liner, 1999; 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 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 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 reflections, including a 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==