Seismic Reflection Examples
|Reduced view of an entire marine seismic record. Note:
|Field recording parameters for the survey. In particular note the diagram of the ship, with the energy source towed behind, and the long streamer array towed behind that.|
|Scales on the two axes.
On the top of the diagram, numbers show:
At selected points on the top, you get
|Common artefact in reflection profiling, a "bow tie". Note the explanation on the left.|
| Annotated record . The strongest
reflectors will be sedimentary layers, which should be
relatively horizontal and continuous, and faults, which will tend to dip
much more steeply.
The red line marks a major change in the layers visible in the image. Below that point the sedimentary layering appears much less obvious, and it is likely the bottom might be another kind of rock.
The light blue lines trace some layers in the bedded sedimentary layers. The law of superposition can be used to show that there are older rocks on the right side that are not present on the left side.
|Annotated record tracing two layers. Note that this divides the record into three sequences, and that one in the center pinches out.|
|The green line marks a likely fault surface. Note the strong sedimentary layering to the left and the lack of corresponding layering to the right.|
|Note the two reflections near the water surface, and angular
unconformity below them with beds dipping gently to the right.
Older rocks are just under the surface on the left, with progressively
younger rocks to the right.
Apparent dip. On a single line, you see the apparent dip. This is the true dip only if the seismic line parallels the strike; otherwise the apparent dip will be less than the true dip. In the extreme case, when the line is perpendicular to the strike, the apparent dip will be zero.
|Create a 3D fence diagram
Last revision 12/7/2014