sfsigmoid generates a 2-D synthetic reflectivity model, created by Jon Claerbout.
One of the first occurrences of this model is in SEP-73 sponsor report from 1992, where it appeared in several papers:
- J. F. Claerbout, 1992, Introduction to Kirchhoff Migration Programs: SEP-73 report, 361-366, Stanford Exploration Project.
- J. F. Claerbout, 1992, Filling Data Gaps Using a Local Plane-Wave Model: SEP-73 report, 401-408, Stanford Exploration Project.
- J. F. Claerbout, 1992, Information from Smiles: Mono-Plane-Annihilator Weighted Regression: SEP-73 report, 409-420, Stanford Exploration Project.
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J. F. Claerbout, 1992, Crossline Regridding by Inversion: SEP-73 report, 421-428, Stanford Exploration Project.
The model was described as “a synthetic model that illustrates local variation in bedding. Notice dipping bedding, curved bedding, unconformity between them, and a fault in the curved bedding.” Later, the sigmoid model made an appearance in Claerbout’s book Basic Earth Imaging. The following example from bei/krch/sep73 illustrates the effect of aliasing on Kirchhoff modeling and migration:
The model has appeared in numerous other tests. The following example from tccs/flat/flat shows automatic flattening of the sigmoid model by predictive painting.
sfsigmoid has several parameters that control the model. The usual n1=, n2=, o1=, o2=, d1=, d2= parameters control the mesh size and sampling, taper= indicates whether to taper the sides of the model, large= controls the length of the synthetic reflectivity series. The program takes no input.
