Trace Shift

Description Shift traces vertically.
Module(s) Explorationist, Image Gather Processing
Requirements Volume
Related Trace Padding, NaN Removal, Header Maths, RMO Correction
Works with 2D, Stacks, Gathers

Create Trace Shift process

  1. In the Control Panel, open the Process tab.
  2. Click the blue "+" icon and select New Process.
  3. Search and double-click Trace Shift.
  4. Type a name for the process and click OK.

Define Trace Shift settings

  1. Volume: Select the input data to be shifted.
  2. Type:
    • Bulk shift for a single shift per trace.
    • Volume-based shift for time/depth varying corrections.
  3. Mode:
    • Apply: Positive values shift traces to greater depths/times.
    • Remove: Negative values shift traces to greater depths/times.
  4. Shift (Type: bulk shift): Traces will be shifted according to this value.
    • Constant: A constant shift value to be applied to all traces.
    • Trace Header: A variable shift value, calculated as Header * Scalar + Constant
      • Header: A standard trace header
      • Scalar: The value in the chosen header will be multiplied by this amount
      • Constant: To be added to the scaled header value

This process shifts each trace in TWT according to the value in a specified trace header. The shift amount can optionally be scaled by a multiplier and adjusted by a constant.

For each trace, the amount to shift is: Header * Scalar + Constant

This value will be interpreted as a shift in milliseconds, with a positive value moving the trace deeper (i.e. to a larger TWT).

The process uses sinc interpolation to apply shifts that are not a multiple of the sample interval.

  1. Shifts volume (Type: volume-based shift): Select a volume of time or depth shifts. Ensure this volume sufficiently covers the input volume. This mode will perform very limited linear interpolation/extrapolation for seismic not covered by the shifts volume, but only when not applying header-based trace matching.
  2. Output start/end time: The output traces will cover this time range, at the same sample interval as the input. If Output end time is not in the sequence defined by the Output start time and the sample interval, it will be changed to the nearest lower sequence member.

Interpolation of bulk-shifts will be performed using the same scheme as defined in the input volume class settings. Volume-based shifts use sinc interpolation. When applying shifts, input(t) is moved to output(t+shift(t)). When removing shifts, input(t+shift(t)) is moved to output(t). Note that when using shift volumes, removing a shift of v is not completely identical to applying a shift of -v.

Sample Interpolation

By default vertical interpolation is applied using the same scheme as defined in the input volume class settings. This is controlled by the following two parameters:

  1. Sample interpretation: whether samples are treated as point values (Instantaneous) or as interval values (Top-posted interval).
  2. Vertical interpolation: controls how values are obtained when interpolating between samples.
    • Sinc: Use for seismic data.
    • Edge Detecting: Use for blocky data, e.g. impedance volumes.
    • Lagrangian: Use for smoothly varying data, but not velocities.
    • Linear: Simple linear. Use for ZT and TZ velocity volumes.
    • Nearest
  3. If either parameter is edited, the new value will be retained irrespective of input volume selection or the selected volume's class. To reset this manual selection and return to volume-defined settings, click the reload button.

IMPORTANT: Interpolation of bulk-shifts will be performed using the same scheme as defined in the input volume class settings. Volume-based shifts use sinc interpolation. When applying shifts, input(t) is moved to output(t+shift(t)). When removing shifts, input(t+shift(t)) is moved to output(t). Note that when using shift volumes, removing a shift of v is not completely identical to applying a shift of -v.

Example

If the TSTAT header contains a positive value in microseconds, and you want to shift the traces up (i.e. shallower) by this amount, you would select:

  • Header: TSTAT
  • Scalar: -0.001
  • Constant: 0