Local Trace Alignment

Description Flatten gathers at one window using shifts
Module(s) Gather Attributes
Requirements Volume
Related RMO Correction, Trim Statics, Trace Shift,
Works with Gathers

This process aligns gathers/records by applying a vertical shift to each trace. The shift is calculated using correlation to a target trace over a single window. When creating the target trace by stacking, the target is updated at each iteration using progressively higher frequencies.

Create a Local Trace Alignment process

Create edges
  1. In the Process tab, click the blue "+" icon and select New Process.
  2. Select Local Trace Alignment and type a name for the process.

Configure the process

  1. Volume: Select the gather volume.
  2. (Optional) Output header: If provided, store the final shift in this trace header.
    • TIP: Use a scaled header (i.e. by SCALEL), to provide sub-ms precision. Stored shifts can be reversed using a "Trace Shift" process. When using an unscaled header, shifts are rounded to the nearest millisecond.
  3. Window top/bottom (ms): The start and end of the correlation window
  4. Max shift per iteration (ms): The maximum time shift that can be applied.
    • Choose a large enough value to flatten at the event.
    • If values are too large, it may cycle-skip and correlate to the wrong event.
  5. Iterations: The number of iterations to perform. Each iteration filters the data using progressively-higher frequencies.
  6. High-cut on first/last frequencies: The first and last high-cut frequency values to apply. Iterations step linearly between these values.
  7. Align to:
    • Central Traces: Align to the centre trace of the gather/record
    • Stack of Traces: Align to a stack of the gather/record
  8. (For Stack of Traces) Number of Stack Building Iterations:
    • For the first iteration, the target is a stack of the input.
    • For following iterations, the target is a stack of the input with shifts applied.
    • Shifts are always calculated by correlating the original traces against the current target.