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

       2. Amplitude Normalization 

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

       3. RGB Assignment 

• 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)]

        4. Blending 

• 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.

Dominant Color   Frequency Band  Interpretation

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

Red                        Low (15 Hz)            Thick beds or broad features

Green                    Mid (30 Hz)            Intermediate bed thickness

Blue                       High (60 Hz)         Thin beds or sharp boundaries

Cyan/Magenta    Mixed                      Transition zones or                              

/Yellow/White                                        complex layering

• Channel delineation: channels often show strong color contrast due to frequency attenuation or tuning.
• Thin-bed tuning detection: high-frequency dominance (blue) highlights tuned reflections.
• Facies differentiation: lithologic changes alter dominant frequency response.
• Hydrocarbon indicators: gas-charged sands often exhibit local spectral anomalies.