Spectral Descomposition guide time gate

[efrain andres laverde mera]

Hi everyone. I wonder if there are some way to create a guide spectral descomposition. I mean, I have a horizont of interes and I want to generate a spectral descomposition along the horizont with a time gate of -50 + 50, but with the horizont in the center.

If anyone can give me some advices it would be very valued. Thank you so much.

Efrain Laverde

[Paul de Groot]

Dear Efrain,

There are two possible workflows to do this.

Option 1: only calculate components along the horizon.

1. Add your horizon to the tree and make sure the horizon is selected (i.e. do not click on another object after you added the horizon)
2. Open the 3D Attribute definition window and select Spectral Decomposition.
3. Select Short Window FFT* and define the time-window**. 
4. Add the attribute (let's call it "sd")
5. Press the "Evaluate Attribute" icon.
6. Specify the "Number of steps" and Calculate. 
7. Use the slider to movie-style inspect the components.
8. Set the "Store slices on Accept" toggle to "on" and press Accept***.

Option 2: Decompose an entire volume and then display along a horizon.

1. Open the 3D Attribute definition window and select Spectral Decomposition.
2. Select Short Window FFT* and define the time-window**.
3. Add the attribute (let's call it "sd")
4. Go to Processing -> Create Seismic Output -> Attributes -> Multi-Attribute
5. Select "sd" and select all components. Process the volume.
6. Add the horizon to the tree and add multiple display elements, each filled with a different component from the volume****. 

*You can also use Continuous Wavelet Decomposition on the horizon. CWT does not have a time-gate but it may result in sharper images and hence this is worth testing.

** A time-window of -50 to + 50 means you get a mixed signal from the geologic layers above and below your horizon. If the horizon represents the top of the layer of interest it makes more sense to try an a-symmetric window e.g. -8, +32 to take the convolutional effect into account.

*** The components are stored with the Horizon as "Surface data". Thereafter, you can reload all components into a single display element and use "Pg up" and "Pg dn" keyboard controls to movie-style step through the components. 

**** In both cases you can add a horizon for RGB(A) blending of three components (and a 4th attribute like similarity for the alpha channel).

I hope this helps. Best regards,

Paul.

-- 

Paul de Groot

President

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