Spectral blending

Spectral blending specifically blends spectral decomposition results(e.g., 15 Hz, 30 Hz, 60 Hz) into a color composite.

     1. Spectral Decomposition 

• Compute frequency-dependent amplitude volumes using methods like: 
  • Short-Time Fourier Transform (STFT)
  • Continuous Wavelet Transform (CWT)
  • Matching Pursuit Decomposition (MPD)
• Result → amplitude cubes: A_15Hz, A_30Hz, A_60Hz

• Normalize each frequency amplitude to a consistent dynamic range (e.g., 0–1 or percentile scaling).
• Prevents one band from dominating visually.

• R → Low frequency (e.g., 15 Hz)
• G → Mid frequency (e.g., 30 Hz)
• B → High frequency (e.g., 60 Hz)
• RGB(x,z)=[A15​(x,z),A30​(x,z),A60​(x,z)]

• Combine into a single color image.
• Optionally overlay on amplitude or coherence section for context.

Most seismic interpretation platforms (e.g., Petrel, OpendTect, Kingdom, Geoteric) allow color blending via an RGB panel:You can assign each attribute (or filtered frequency) to a color channel. Adjust the gain or stretch of each to balance intensity.Optionally, use transparency or opacity blending to overlay on amplitude data.Example setup:RGB Channel   Attribute                               Description

========================================================= R Coherence                 (Faults and discontinuities)

G  Curvature                  (Structural deformation)

B  Sweetness                 ((AVO) Lithologic variation or 

                                             hydrocarbon indicator).

=========================================================

This composite allows simultaneous visualization of structure, stratigraphy, and lithology.

frequency decomposition algorithms are classified in there methods:

• Constant Bandwidth
• Constant Q
• High Definition Frequency Decomposition

The Constant Bandwidth algorithm uses a constant filter length defined by the lowest central frequency set by the user and offers the highest frequency resolution, but it is the weakest when it comes to vertical resolving power. The Constant Q algorithm utilities a variable filter length, thus a variable bandwidth, and has a better vertical resolution than the previous approach. The best vertical resolution is provided by the High Definition Frequency Decomposition (HDFD). 

 The quickest way to a useful frequency decomposition color blend is to use the Exponential Constant Q option in the Frequency Decomposition workflow. A reference time slice should be chosen to reflect the potentially most prospective interval. Generate a spectrum along this time slice, then modify the minimum and maximum frequencies so that they correspond to frequency values where the power spectrum reaches 30-50% of its peak value (note that the vertical axis of the graph is divided into 10 equal intervals). 

Once an object of interest has been identified, the combined frequencies can be selected in a more focused manner. 

Another way to optimize the frequencies for a color blend is to visually compare the different frequency magnitude responses in the Data Preview window of the Frequency Decomposition tool.