Diffractions, statics, and downward continuation
Repeated acquisition experiments when the elevation of the surface is lowered to one scatterpoint
Diffraction estimation at various depths using surface measurements.
Assume the source and receiver arrays are lowered into the earth at the levels indicated on the left side of the geological model.
Sketch the seismic image on the following time sections for the appropriate depths.
Copy the zero-time energy to the corresponding depth section below.
Compare the migrated depth section with the original geology.
the data always remains as a time section
only the top edge of the time section is copied to the migrated section
this top edge is referred to as the imaging condition.
Estimating the downward layer diffraction from the surface diffraction using vertical elevation corrections.
Generalized diffraction estimation using all possible ray path correction.
Figures & Tables
This volume, SEG Course Notes Series No. 13, is designed to give the practicing geophysicist an understanding of the principles of poststack migration, presented with intuitive reasoning rather than laborious math. Modeling is introduced as a natural process that starts with a geologic model and then builds seismic data. Migration is then described as the reverse process that uses seismic data to find the geologic model. Many other topics are covered relating to the quality of the migrated section, such as aliasing, rugged topography, or use of the correct velocity. Significant new material has been added in this revised edition of the original 1997 book, especially algorithms based on the phase-shift method, such as PSPI and the omegaX method.