Purpose: Analyze seismic data at different vertical scales. Typically applied to horizons to visualize thickness variations at sub-seismic resolution. Theory: When the thickness of an acoustic layer falls in the tuning range the seismic amplitude increases due to interference of top and bottom reflections. If you decompose the seismic response into its frequency components (or into wavelet scales) the largest amplitude corresponds to the layer's tuning range, hence, to its thickness. In this way, it is possible to interpret thickness variations at sub-seismic resolution by decomposing an interval around a mapped horizon. Software: OpendTect
Workflow:
Add an element (horizon) to the tree.
Open the Attribute Set window and add Spectral Decomposition to the list.
Press the Evaluate Attribute icon to calculate the individual components (frequencies or wavelet scales).
Use the slider to movie-style inspect the components. Pressing Accept updates the Attribute definition to calculate this component only.
To use individual components for further work (e.g. to create a cube for frequency 10Hz) you must define each component as a separate attribute in the list.
Tips:
Spectral Decomposition applied to a horizon takes time. Use the "Store slices on Accept" option to save all components as Surface data belonging to that Horizon for later use. To scroll through Surface data use the Pg Up and Pg down keys.
Color blended display: RGBA blending attribute display is used to create a normalized color-blended display that often show features with greater clarity and enhances a detail map view. The user can blend the iso-frequency responses (Spectral Decomposition). For more information go to RGB display