Semblance (Velocity)
This process creates a velocity-semblance gather by calculating the semblance for each input gather over a range of NMO velocities. The Velocity Picking window includes the same semblance velocity spectra in the default display.
See Velocity Picking for additional details on picking velocities and semblance calculations.
![](https://media.screensteps.com/image_assets/assets/002/653/080/original/22624604-1835-4efb-9793-0f73f2d4991f.png)
- In the Control Panel, open the Process tab.
- At the tab header, click the Add icon and select New Process.
- Scroll down and double-click on Semblance (velocity).
- Type a name for the process and click OK.
Configure the Semblance (Velocity) process
![](https://media.screensteps.com/image_assets/assets/002/653/102/original/08c0bf49-dd45-4b77-9f8c-6a958361804e.png)
- Volume: Select the input gathers to analyse.
- Window Length: The length of the window for the semblance calculation.
- Offset Weighting Power: Increase the weighting of far offsets.
- Normalise: When enabled, normalise the semblance at each time to [ 0.0 to 1.0 ] (for each gather).
- TWT (ms): The maximum time and increment for the calculated semblance gather.
![](https://media.screensteps.com/image_assets/assets/002/653/084/original/17d55f36-a8f9-46e3-aa21-ef830ac68fa6.png)
- Velocity: The range of NMO velocities to test
a. For gathers without NMO correction, use absolute velocities:
![](https://media.screensteps.com/image_assets/assets/002/653/083/original/03f93dab-30bb-4143-8846-8ec07eaf7f49.png)
b. For gathers with NMO correction applied, use relative velocities:
![](https://media.screensteps.com/image_assets/assets/002/653/076/original/bd8ada16-f6e2-433c-b777-48654a07c3dd.png)
- NMO: The NMO model and order to apply, with an optional Stretch Mute.
![](https://media.screensteps.com/image_assets/assets/002/653/079/original/972ac62b-d64a-46c1-a35f-ead5a6e744ae.png)
- Mute: Select inner and outer mutes to apply to the gathers before calculating the semblance.
![](https://media.screensteps.com/image_assets/assets/002/653/075/original/24d9e618-f153-4ffe-9cef-2411f26561dc.png)