Semblance (Velocity)

Description Create semblance velocity spectra gathers for a range of velocities.
Module(s) Explorationist, Image Gather Processing Gather Attributes
Requirements Volume
Related NMO, RMO Velocity Picking
Works with Gathers

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.

  1. In the Control Panel, open the Process tab.
  2. At the tab header, click the Add icon and select New Process.
  3. Scroll down and double-click on Semblance (velocity).
  4. Type a name for the process and click OK.

Configure the Semblance (Velocity) process

  1. Volume: Select the input gathers to analyse.
  2. Window Length: The length of the window for the semblance calculation.
  3. Offset Weighting Power: Increase the weighting of far offsets.
  4. Normalise: When enabled, normalise the semblance at each time to [ 0.0 to 1.0 ] (for each gather).
  5. TWT (ms): The maximum time and increment for the calculated semblance gather.
  1. Velocity: The range of NMO velocities to test

a. For gathers without NMO correction, use absolute velocities:

b. For gathers with NMO correction applied, use relative velocities:

  1. NMO: The NMO model and order to apply, with an optional Stretch Mute.
  1. Mute: Select inner and outer mutes to apply to the gathers before calculating the semblance.