Diffraction Stack Modeling Lab
(Top) Syncline reflectivity model and (bottom) ZO seismic traces.
OBJECTIVE: Generate Zero-Offset (ZO) synthetic data with a MATLAB script
that computes diffraction stack (DS) modeling.
Reinforce idea that DS only models primaries, accounts for diffractions, and
follows theoretical formula.
- Load into your working directory all MATLAB scripts. The important MATLAB scripts are for diffraction stack modeling (zomodel.m), Ricker wavelet generator (ricker.m), and ZO data modeler (model1.m). Name each file by their names given above.
- In MATLAB, type "zomodel" to generate ZO synthetic data for a syncline model. Data are in 1-way travel time. To examine the reflectivity model simply type "imagesc(MIG')". Examine the model1.m code and convince yourself that it honors the diffraction stack algorithm.
- Spurious diffraction energy will appear on data if the distance between adjacent scatterers is too coarse. Try to figure out rough rule of thumb for grid size and wavelength so a string of scatterers can faithfully represent the ZO reflections without unwanted spurious diffractions.
- Different Models: Go into zomodel.m and design your favorite model. Then run the programs again.
- Insert the obliquity factor in the forward modeling code (i.e., cos(theta) where theta is the angle between
source-image ray and neormal to surface where geophones are located). What is the effect of the obliquity factor?