Faulting

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Problem

How do you reconcile the contradictory dips between the 5- and 6-km marks at the top of the migrated section in Figure 10.4a? What structural style is represented? How would you draw faults?

Background

Structural style is discussed in problem 10.3.

When a burst of energy occurs on only a few traces, it migrates into a wavefront shape, called a smile; the pattern on Figure 10.4a below 3 s is mainly one of intersecting smiles.

Figure 10.4a.  Ardmore Basin (Oklahoma) section.
Figure 10.4b.  Interpretation of Figure 10.4a.

Solution

This section has been migrated, as is evident from the many “smiles” in the lower portion of the section. Migration generally assumes that

  1. the line is in the dip direction so that there are no data from off to the side of the line
  2. the velocities used are correct
  3. all of the data arise from primary reflections or diffractions.

If some of these assumptions are not true, the result is conflicting dips, which are abundant on this section. There is no obvious correlation of events at opposite sides of the section.

This structure can be interpreted as a flower structure (solid lines in Figure 10.4b), a structure resulting from a compressional component (or extensional component for a negative flower structure) of strike-slip faulting. If this is the case, the structural style would be classed as basement-involved wrench faulting. The structure may also be interpreted as thrust faulting (dashed line in Figure 10.4b), in which case it would be classed as basement-detached thrusting.

Knowledge of the structural style from other data would help in properly interpreting this line.

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Structural style Mapping faults using a grid of lines
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Data processing Refraction methods

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