How to estimate seismic bandwidth using spectral decomposition?
Workflow
![](https://media.screensteps.com/image_assets/assets/003/281/945/original/dbcdf46e-76c0-44ac-a8dc-0482aba5e56d.png)
Calculate the Spectral Decomposition result:
- Click the Process tab, click the blue "+" button and add a Spectral Decomposition process.
- Select an Input Volume.
- Pay attention to the Spectral Decomposition frequency interval, it's needed for the last step.
![](https://media.screensteps.com/image_assets/assets/003/281/948/original/079d7da5-b9b1-498b-985a-70cf3ef187aa.png)
Apply a gate / threshold function to specify the minimum amplitude to qualify for inclusion.
- Click the blue "+" button and add a Volume Maths process.
- In the details panel, add a symbol and select the result from the previous process.
- Use formula: if (v1 > 20000, 2, 1)
- Tune this threshold to adjust your results. This example uses 20,000, but it will vary depending on your spectral decomposition amplitudes.
Note: The gate uses values of 1 & 2 to avoid creating "missing values" in the stacking.
![](https://media.screensteps.com/image_assets/assets/003/281/944/original/91ec5dd5-0ac1-47fb-9e05-ac74d0df0f5b.png)
Stack the gated result (in effect counting the number of frequencies above the threshold).
- Click the blue "+" button and add a Stacking process.
- In the details panel, select the result from the previous Volume Maths process in the volume search box.
![](https://media.screensteps.com/image_assets/assets/003/281/949/original/28a30406-262f-47c6-ba5b-0482a99568c0.png)
Rescale the stack by the number of stacked traces (NHS trace header) and the frequency interval from step 1. This gives the bandwidth estimate.
- Click the blue "+" button and add a Volume Maths process.
- In the details panel, add a symbol and select the result from the Stacking process.
- Use formula: (v1 - 1) * 3 * NHS
Note: A constant 1 value is subtracted from the stack to account for the 1-2 range of the gate. For this example, the value 3 is the frequency interval from step 1.
Results
![](https://media.screensteps.com/image_assets/assets/003/281/946/original/f5a913e9-a767-49c2-937f-a19dbf53e50e.png)
![](https://media.screensteps.com/image_assets/assets/003/281/947/original/a3d3f2a2-a6b0-4a4d-8ef0-86c5f9e68f38.png)